diff --git a/core/block.ts b/core/block.ts
index 499cdaef0..f648674d2 100644
--- a/core/block.ts
+++ b/core/block.ts
@@ -12,51 +12,51 @@
  * The class representing one block.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Block');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_change.js';
+import './events/events_block_change';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_create.js';
+import './events/events_block_create';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_delete.js';
+import './events/events_block_delete';
 
-import {Blocks} from './blocks.js';
+import {Blocks} from './blocks';
 /* eslint-disable-next-line no-unused-vars */
-import {Comment} from './comment.js';
-import * as common from './common.js';
-import {Connection} from './connection.js';
-import {ConnectionType} from './connection_type.js';
-import * as constants from './constants.js';
+import {Comment} from './comment';
+import * as common from './common';
+import {Connection} from './connection';
+import {ConnectionType} from './connection_type';
+import * as constants from './constants';
 /* eslint-disable-next-line no-unused-vars */
-import {Abstract} from './events/events_abstract.js';
+import {Abstract} from './events/events_abstract';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockMove} from './events/events_block_move.js';
-import * as eventUtils from './events/utils.js';
-import * as Extensions from './extensions.js';
+import {BlockMove} from './events/events_block_move';
+import * as eventUtils from './events/utils';
+import * as Extensions from './extensions';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import {Align, Input} from './input.js';
-import {inputTypes} from './input_types.js';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import {Align, Input} from './input';
+import {inputTypes} from './input_types';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocation} from './interfaces/i_ast_node_location.js';
+import {IASTNodeLocation} from './interfaces/i_ast_node_location';
 /* eslint-disable-next-line no-unused-vars */
-import {IDeletable} from './interfaces/i_deletable.js';
-import {ASTNode} from './keyboard_nav/ast_node.js';
+import {IDeletable} from './interfaces/i_deletable';
+import {ASTNode} from './keyboard_nav/ast_node';
 /* eslint-disable-next-line no-unused-vars */
-import {Mutator} from './mutator.js';
-import * as Tooltip from './tooltip.js';
-import * as arrayUtils from './utils/array.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as idGenerator from './utils/idgenerator.js';
-import * as parsing from './utils/parsing.js';
-import {Size} from './utils/size.js';
+import {Mutator} from './mutator';
+import * as Tooltip from './tooltip';
+import * as arrayUtils from './utils/array';
+import {Coordinate} from './utils/coordinate';
+import * as idGenerator from './utils/idgenerator';
+import * as parsing from './utils/parsing';
+import {Size} from './utils/size';
 /* eslint-disable-next-line no-unused-vars */
-import {VariableModel} from './variable_model.js';
+import {VariableModel} from './variable_model';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 
 
 /**
diff --git a/core/block_animations.ts b/core/block_animations.ts
index 105f771e8..83beded81 100644
--- a/core/block_animations.ts
+++ b/core/block_animations.ts
@@ -12,13 +12,13 @@
  * Methods animating a block on connection and disconnection.
  * @namespace Blockly.blockAnimations
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.blockAnimations');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as dom from './utils/dom.js';
-import {Svg} from './utils/svg.js';
+import {BlockSvg} from './block_svg';
+import * as dom from './utils/dom';
+import {Svg} from './utils/svg';
 
 
 /** A bounding box for a cloned block. */
diff --git a/core/block_drag_surface.ts b/core/block_drag_surface.ts
index cca671a6f..2f8595bc2 100644
--- a/core/block_drag_surface.ts
+++ b/core/block_drag_surface.ts
@@ -22,13 +22,13 @@
  * while dragging blocks.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.BlockDragSurfaceSvg');
 
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {Svg} from './utils/svg.js';
-import * as svgMath from './utils/svg_math.js';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {Svg} from './utils/svg';
+import * as svgMath from './utils/svg_math';
 
 
 /**
diff --git a/core/block_dragger.ts b/core/block_dragger.ts
index 7f6537ea0..b1fd69c70 100644
--- a/core/block_dragger.ts
+++ b/core/block_dragger.ts
@@ -12,32 +12,32 @@
  * Methods for dragging a block visually.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.BlockDragger');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_drag.js';
+import './events/events_block_drag';
 
-import * as blockAnimation from './block_animations.js';
+import * as blockAnimation from './block_animations';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as bumpObjects from './bump_objects.js';
-import * as common from './common.js';
+import {BlockSvg} from './block_svg';
+import * as bumpObjects from './bump_objects';
+import * as common from './common';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockMove} from './events/events_block_move.js';
-import * as eventUtils from './events/utils.js';
+import {BlockMove} from './events/events_block_move';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {Icon} from './icon.js';
-import {InsertionMarkerManager} from './insertion_marker_manager.js';
+import {Icon} from './icon';
+import {InsertionMarkerManager} from './insertion_marker_manager';
 /* eslint-disable-next-line no-unused-vars */
-import {IBlockDragger} from './interfaces/i_block_dragger.js';
+import {IBlockDragger} from './interfaces/i_block_dragger';
 /* eslint-disable-next-line no-unused-vars */
-import {IDragTarget} from './interfaces/i_drag_target.js';
-import * as registry from './registry.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
+import {IDragTarget} from './interfaces/i_drag_target';
+import * as registry from './registry';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/block_svg.ts b/core/block_svg.ts
index da46dc61d..63c31ae81 100644
--- a/core/block_svg.ts
+++ b/core/block_svg.ts
@@ -12,72 +12,72 @@
  * Methods for graphically rendering a block as SVG.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.BlockSvg');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './theme.js';
+import './theme';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_selected.js';
+import './events/events_selected';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './touch.js';
+import './touch';
 
-import {Block} from './block.js';
-import * as blockAnimations from './block_animations.js';
-import * as browserEvents from './browser_events.js';
+import {Block} from './block';
+import * as blockAnimations from './block_animations';
+import * as browserEvents from './browser_events';
 /* eslint-disable-next-line no-unused-vars */
-import {Comment} from './comment.js';
-import * as common from './common.js';
-import {config} from './config.js';
+import {Comment} from './comment';
+import * as common from './common';
+import {config} from './config';
 /* eslint-disable-next-line no-unused-vars */
-import {Connection} from './connection.js';
-import {ConnectionType} from './connection_type.js';
-import * as constants from './constants.js';
-import * as ContextMenu from './contextmenu.js';
-import {ContextMenuOption, ContextMenuRegistry, LegacyContextMenuOption} from './contextmenu_registry.js';
+import {Connection} from './connection';
+import {ConnectionType} from './connection_type';
+import * as constants from './constants';
+import * as ContextMenu from './contextmenu';
+import {ContextMenuOption, ContextMenuRegistry, LegacyContextMenuOption} from './contextmenu_registry';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockMove} from './events/events_block_move.js';
-import * as eventUtils from './events/utils.js';
+import {BlockMove} from './events/events_block_move';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from './field.js';
-import {FieldLabel} from './field_label.js';
+import {Field} from './field';
+import {FieldLabel} from './field_label';
 /* eslint-disable-next-line no-unused-vars */
-import {Icon} from './icon.js';
+import {Icon} from './icon';
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from './input.js';
+import {Input} from './input';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocationSvg} from './interfaces/i_ast_node_location_svg.js';
+import {IASTNodeLocationSvg} from './interfaces/i_ast_node_location_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {IBoundedElement} from './interfaces/i_bounded_element.js';
-import {CopyData, ICopyable} from './interfaces/i_copyable.js';
+import {IBoundedElement} from './interfaces/i_bounded_element';
+import {CopyData, ICopyable} from './interfaces/i_copyable';
 /* eslint-disable-next-line no-unused-vars */
-import {IDraggable} from './interfaces/i_draggable.js';
-import * as internalConstants from './internal_constants.js';
-import {ASTNode} from './keyboard_nav/ast_node.js';
-import {TabNavigateCursor} from './keyboard_nav/tab_navigate_cursor.js';
-import {MarkerManager} from './marker_manager.js';
-import {Msg} from './msg.js';
+import {IDraggable} from './interfaces/i_draggable';
+import * as internalConstants from './internal_constants';
+import {ASTNode} from './keyboard_nav/ast_node';
+import {TabNavigateCursor} from './keyboard_nav/tab_navigate_cursor';
+import {MarkerManager} from './marker_manager';
+import {Msg} from './msg';
 /* eslint-disable-next-line no-unused-vars */
-import {Mutator} from './mutator.js';
-import {RenderedConnection} from './rendered_connection.js';
+import {Mutator} from './mutator';
+import {RenderedConnection} from './rendered_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {Debug as BlockRenderingDebug} from './renderers/common/debugger.js';
+import {Debug as BlockRenderingDebug} from './renderers/common/debugger';
 /* eslint-disable-next-line no-unused-vars */
-import {IPathObject} from './renderers/common/i_path_object.js';
-import * as blocks from './serialization/blocks.js';
-import {BlockStyle} from './theme.js';
-import * as Tooltip from './tooltip.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {Rect} from './utils/rect.js';
-import {Svg} from './utils/svg.js';
-import * as svgMath from './utils/svg_math.js';
+import {IPathObject} from './renderers/common/i_path_object';
+import * as blocks from './serialization/blocks';
+import {BlockStyle} from './theme';
+import * as Tooltip from './tooltip';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {Rect} from './utils/rect';
+import {Svg} from './utils/svg';
+import * as svgMath from './utils/svg_math';
 /* eslint-disable-next-line no-unused-vars */
-import {Warning} from './warning.js';
-import {Workspace} from './workspace.js';
+import {Warning} from './warning';
+import {Workspace} from './workspace';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/blockly.ts b/core/blockly.ts
index 24a87e9f9..a117c01e5 100644
--- a/core/blockly.ts
+++ b/core/blockly.ts
@@ -12,171 +12,171 @@
  * The top level namespace used to access the Blockly library.
  * @namespace Blockly
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_create.js';
+import './events/events_block_create';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/workspace_events.js';
+import './events/workspace_events';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_ui.js';
+import './events/events_ui';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_ui_base.js';
+import './events/events_ui_base';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_var_create.js';
+import './events/events_var_create';
 
-import {Block} from './block.js';
-import * as blockAnimations from './block_animations.js';
-import {BlockDragSurfaceSvg} from './block_drag_surface.js';
-import {BlockDragger} from './block_dragger.js';
-import {BlockSvg} from './block_svg.js';
-import {BlocklyOptions} from './blockly_options.js';
-import {Blocks} from './blocks.js';
-import * as browserEvents from './browser_events.js';
-import {Bubble} from './bubble.js';
-import {BubbleDragger} from './bubble_dragger.js';
-import * as bumpObjects from './bump_objects.js';
-import * as clipboard from './clipboard.js';
-import {Comment} from './comment.js';
-import * as common from './common.js';
-import {ComponentManager} from './component_manager.js';
-import {config} from './config.js';
-import {Connection} from './connection.js';
-import {ConnectionChecker} from './connection_checker.js';
-import {ConnectionDB} from './connection_db.js';
-import {ConnectionType} from './connection_type.js';
-import * as ContextMenu from './contextmenu.js';
-import * as ContextMenuItems from './contextmenu_items.js';
-import {ContextMenuRegistry} from './contextmenu_registry.js';
-import * as Css from './css.js';
-import {DeleteArea} from './delete_area.js';
-import * as dialog from './dialog.js';
-import {DragTarget} from './drag_target.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import * as Events from './events/events.js';
-import * as Extensions from './extensions.js';
-import {Field} from './field.js';
-import {FieldAngle} from './field_angle.js';
-import {FieldCheckbox} from './field_checkbox.js';
-import {FieldColour} from './field_colour.js';
-import {FieldDropdown} from './field_dropdown.js';
-import {FieldImage} from './field_image.js';
-import {FieldLabel} from './field_label.js';
-import {FieldLabelSerializable} from './field_label_serializable.js';
-import {FieldMultilineInput} from './field_multilineinput.js';
-import {FieldNumber} from './field_number.js';
-import * as fieldRegistry from './field_registry.js';
-import {FieldTextInput} from './field_textinput.js';
-import {FieldVariable} from './field_variable.js';
-import {Flyout} from './flyout_base.js';
-import {FlyoutButton} from './flyout_button.js';
-import {HorizontalFlyout} from './flyout_horizontal.js';
-import {FlyoutMetricsManager} from './flyout_metrics_manager.js';
-import {VerticalFlyout} from './flyout_vertical.js';
-import {Generator} from './generator.js';
-import {Gesture} from './gesture.js';
-import {Grid} from './grid.js';
-import {Icon} from './icon.js';
-import {inject} from './inject.js';
-import {Align, Input} from './input.js';
-import {inputTypes} from './input_types.js';
-import {InsertionMarkerManager} from './insertion_marker_manager.js';
-import {IASTNodeLocation} from './interfaces/i_ast_node_location.js';
-import {IASTNodeLocationSvg} from './interfaces/i_ast_node_location_svg.js';
-import {IASTNodeLocationWithBlock} from './interfaces/i_ast_node_location_with_block.js';
-import {IAutoHideable} from './interfaces/i_autohideable.js';
-import {IBlockDragger} from './interfaces/i_block_dragger.js';
-import {IBoundedElement} from './interfaces/i_bounded_element.js';
-import {IBubble} from './interfaces/i_bubble.js';
-import {ICollapsibleToolboxItem} from './interfaces/i_collapsible_toolbox_item.js';
-import {IComponent} from './interfaces/i_component.js';
-import {IConnectionChecker} from './interfaces/i_connection_checker.js';
-import {IContextMenu} from './interfaces/i_contextmenu.js';
-import {ICopyable} from './interfaces/i_copyable.js';
-import {IDeletable} from './interfaces/i_deletable.js';
-import {IDeleteArea} from './interfaces/i_delete_area.js';
-import {IDragTarget} from './interfaces/i_drag_target.js';
-import {IDraggable} from './interfaces/i_draggable.js';
-import {IFlyout} from './interfaces/i_flyout.js';
-import {IKeyboardAccessible} from './interfaces/i_keyboard_accessible.js';
-import {IMetricsManager} from './interfaces/i_metrics_manager.js';
-import {IMovable} from './interfaces/i_movable.js';
-import {IPositionable} from './interfaces/i_positionable.js';
-import {IRegistrable} from './interfaces/i_registrable.js';
-import {IRegistrableField} from './interfaces/i_registrable_field.js';
-import {ISelectable} from './interfaces/i_selectable.js';
-import {ISelectableToolboxItem} from './interfaces/i_selectable_toolbox_item.js';
-import {ISerializer as SerializerInterface} from './interfaces/i_serializer.js';
-import {IStyleable} from './interfaces/i_styleable.js';
-import {IToolbox} from './interfaces/i_toolbox.js';
-import {IToolboxItem} from './interfaces/i_toolbox_item.js';
-import * as internalConstants from './internal_constants.js';
-import {ASTNode} from './keyboard_nav/ast_node.js';
-import {BasicCursor} from './keyboard_nav/basic_cursor.js';
-import {Cursor} from './keyboard_nav/cursor.js';
-import {Marker} from './keyboard_nav/marker.js';
-import {TabNavigateCursor} from './keyboard_nav/tab_navigate_cursor.js';
-import {MarkerManager} from './marker_manager.js';
-import {Menu} from './menu.js';
-import {MenuItem} from './menuitem.js';
-import {MetricsManager} from './metrics_manager.js';
-import {Msg} from './msg.js';
-import {Mutator} from './mutator.js';
-import {Names} from './names.js';
-import {Options} from './options.js';
-import * as uiPosition from './positionable_helpers.js';
-import * as Procedures from './procedures.js';
-import * as registry from './registry.js';
-import {RenderedConnection} from './rendered_connection.js';
-import * as blockRendering from './renderers/common/block_rendering.js';
-import * as constants from './renderers/common/constants.js';
-import * as geras from './renderers/geras/geras.js';
-import * as minimalist from './renderers/minimalist/minimalist.js';
-import * as thrasos from './renderers/thrasos/thrasos.js';
-import * as zelos from './renderers/zelos/zelos.js';
-import {Scrollbar} from './scrollbar.js';
-import {ScrollbarPair} from './scrollbar_pair.js';
-import * as serializationBlocks from './serialization/blocks.js';
-import * as serializationExceptions from './serialization/exceptions.js';
-import * as serializationPriorities from './serialization/priorities.js';
-import * as serializationRegistry from './serialization/registry.js';
-import * as serializationVariables from './serialization/variables.js';
-import * as serializationWorkspaces from './serialization/workspaces.js';
-import * as ShortcutItems from './shortcut_items.js';
-import {ShortcutRegistry} from './shortcut_registry.js';
-import {Theme} from './theme.js';
-import * as Themes from './theme/themes.js';
-import {ThemeManager} from './theme_manager.js';
-import {ToolboxCategory} from './toolbox/category.js';
-import {CollapsibleToolboxCategory} from './toolbox/collapsible_category.js';
-import {ToolboxSeparator} from './toolbox/separator.js';
-import {Toolbox} from './toolbox/toolbox.js';
-import {ToolboxItem} from './toolbox/toolbox_item.js';
-import * as Tooltip from './tooltip.js';
-import * as Touch from './touch.js';
-import {TouchGesture} from './touch_gesture.js';
-import {Trashcan} from './trashcan.js';
-import * as utils from './utils.js';
-import * as colour from './utils/colour.js';
-import * as deprecation from './utils/deprecation.js';
-import * as svgMath from './utils/svg_math.js';
-import * as toolbox from './utils/toolbox.js';
-import {VariableMap} from './variable_map.js';
-import {VariableModel} from './variable_model.js';
-import * as Variables from './variables.js';
-import * as VariablesDynamic from './variables_dynamic.js';
-import {Warning} from './warning.js';
-import * as WidgetDiv from './widgetdiv.js';
-import {Workspace} from './workspace.js';
-import {WorkspaceAudio} from './workspace_audio.js';
-import {WorkspaceComment} from './workspace_comment.js';
-import {WorkspaceCommentSvg} from './workspace_comment_svg.js';
-import {WorkspaceDragSurfaceSvg} from './workspace_drag_surface_svg.js';
-import {WorkspaceDragger} from './workspace_dragger.js';
-import {resizeSvgContents as realResizeSvgContents, WorkspaceSvg} from './workspace_svg.js';
-import * as Xml from './xml.js';
-import {ZoomControls} from './zoom_controls.js';
+import {Block} from './block';
+import * as blockAnimations from './block_animations';
+import {BlockDragSurfaceSvg} from './block_drag_surface';
+import {BlockDragger} from './block_dragger';
+import {BlockSvg} from './block_svg';
+import {BlocklyOptions} from './blockly_options';
+import {Blocks} from './blocks';
+import * as browserEvents from './browser_events';
+import {Bubble} from './bubble';
+import {BubbleDragger} from './bubble_dragger';
+import * as bumpObjects from './bump_objects';
+import * as clipboard from './clipboard';
+import {Comment} from './comment';
+import * as common from './common';
+import {ComponentManager} from './component_manager';
+import {config} from './config';
+import {Connection} from './connection';
+import {ConnectionChecker} from './connection_checker';
+import {ConnectionDB} from './connection_db';
+import {ConnectionType} from './connection_type';
+import * as ContextMenu from './contextmenu';
+import * as ContextMenuItems from './contextmenu_items';
+import {ContextMenuRegistry} from './contextmenu_registry';
+import * as Css from './css';
+import {DeleteArea} from './delete_area';
+import * as dialog from './dialog';
+import {DragTarget} from './drag_target';
+import * as dropDownDiv from './dropdowndiv';
+import * as Events from './events/events';
+import * as Extensions from './extensions';
+import {Field} from './field';
+import {FieldAngle} from './field_angle';
+import {FieldCheckbox} from './field_checkbox';
+import {FieldColour} from './field_colour';
+import {FieldDropdown} from './field_dropdown';
+import {FieldImage} from './field_image';
+import {FieldLabel} from './field_label';
+import {FieldLabelSerializable} from './field_label_serializable';
+import {FieldMultilineInput} from './field_multilineinput';
+import {FieldNumber} from './field_number';
+import * as fieldRegistry from './field_registry';
+import {FieldTextInput} from './field_textinput';
+import {FieldVariable} from './field_variable';
+import {Flyout} from './flyout_base';
+import {FlyoutButton} from './flyout_button';
+import {HorizontalFlyout} from './flyout_horizontal';
+import {FlyoutMetricsManager} from './flyout_metrics_manager';
+import {VerticalFlyout} from './flyout_vertical';
+import {Generator} from './generator';
+import {Gesture} from './gesture';
+import {Grid} from './grid';
+import {Icon} from './icon';
+import {inject} from './inject';
+import {Align, Input} from './input';
+import {inputTypes} from './input_types';
+import {InsertionMarkerManager} from './insertion_marker_manager';
+import {IASTNodeLocation} from './interfaces/i_ast_node_location';
+import {IASTNodeLocationSvg} from './interfaces/i_ast_node_location_svg';
+import {IASTNodeLocationWithBlock} from './interfaces/i_ast_node_location_with_block';
+import {IAutoHideable} from './interfaces/i_autohideable';
+import {IBlockDragger} from './interfaces/i_block_dragger';
+import {IBoundedElement} from './interfaces/i_bounded_element';
+import {IBubble} from './interfaces/i_bubble';
+import {ICollapsibleToolboxItem} from './interfaces/i_collapsible_toolbox_item';
+import {IComponent} from './interfaces/i_component';
+import {IConnectionChecker} from './interfaces/i_connection_checker';
+import {IContextMenu} from './interfaces/i_contextmenu';
+import {ICopyable} from './interfaces/i_copyable';
+import {IDeletable} from './interfaces/i_deletable';
+import {IDeleteArea} from './interfaces/i_delete_area';
+import {IDragTarget} from './interfaces/i_drag_target';
+import {IDraggable} from './interfaces/i_draggable';
+import {IFlyout} from './interfaces/i_flyout';
+import {IKeyboardAccessible} from './interfaces/i_keyboard_accessible';
+import {IMetricsManager} from './interfaces/i_metrics_manager';
+import {IMovable} from './interfaces/i_movable';
+import {IPositionable} from './interfaces/i_positionable';
+import {IRegistrable} from './interfaces/i_registrable';
+import {IRegistrableField} from './interfaces/i_registrable_field';
+import {ISelectable} from './interfaces/i_selectable';
+import {ISelectableToolboxItem} from './interfaces/i_selectable_toolbox_item';
+import {ISerializer as SerializerInterface} from './interfaces/i_serializer';
+import {IStyleable} from './interfaces/i_styleable';
+import {IToolbox} from './interfaces/i_toolbox';
+import {IToolboxItem} from './interfaces/i_toolbox_item';
+import * as internalConstants from './internal_constants';
+import {ASTNode} from './keyboard_nav/ast_node';
+import {BasicCursor} from './keyboard_nav/basic_cursor';
+import {Cursor} from './keyboard_nav/cursor';
+import {Marker} from './keyboard_nav/marker';
+import {TabNavigateCursor} from './keyboard_nav/tab_navigate_cursor';
+import {MarkerManager} from './marker_manager';
+import {Menu} from './menu';
+import {MenuItem} from './menuitem';
+import {MetricsManager} from './metrics_manager';
+import {Msg} from './msg';
+import {Mutator} from './mutator';
+import {Names} from './names';
+import {Options} from './options';
+import * as uiPosition from './positionable_helpers';
+import * as Procedures from './procedures';
+import * as registry from './registry';
+import {RenderedConnection} from './rendered_connection';
+import * as blockRendering from './renderers/common/block_rendering';
+import * as constants from './renderers/common/constants';
+import * as geras from './renderers/geras/geras';
+import * as minimalist from './renderers/minimalist/minimalist';
+import * as thrasos from './renderers/thrasos/thrasos';
+import * as zelos from './renderers/zelos/zelos';
+import {Scrollbar} from './scrollbar';
+import {ScrollbarPair} from './scrollbar_pair';
+import * as serializationBlocks from './serialization/blocks';
+import * as serializationExceptions from './serialization/exceptions';
+import * as serializationPriorities from './serialization/priorities';
+import * as serializationRegistry from './serialization/registry';
+import * as serializationVariables from './serialization/variables';
+import * as serializationWorkspaces from './serialization/workspaces';
+import * as ShortcutItems from './shortcut_items';
+import {ShortcutRegistry} from './shortcut_registry';
+import {Theme} from './theme';
+import * as Themes from './theme/themes';
+import {ThemeManager} from './theme_manager';
+import {ToolboxCategory} from './toolbox/category';
+import {CollapsibleToolboxCategory} from './toolbox/collapsible_category';
+import {ToolboxSeparator} from './toolbox/separator';
+import {Toolbox} from './toolbox/toolbox';
+import {ToolboxItem} from './toolbox/toolbox_item';
+import * as Tooltip from './tooltip';
+import * as Touch from './touch';
+import {TouchGesture} from './touch_gesture';
+import {Trashcan} from './trashcan';
+import * as utils from './utils';
+import * as colour from './utils/colour';
+import * as deprecation from './utils/deprecation';
+import * as svgMath from './utils/svg_math';
+import * as toolbox from './utils/toolbox';
+import {VariableMap} from './variable_map';
+import {VariableModel} from './variable_model';
+import * as Variables from './variables';
+import * as VariablesDynamic from './variables_dynamic';
+import {Warning} from './warning';
+import * as WidgetDiv from './widgetdiv';
+import {Workspace} from './workspace';
+import {WorkspaceAudio} from './workspace_audio';
+import {WorkspaceComment} from './workspace_comment';
+import {WorkspaceCommentSvg} from './workspace_comment_svg';
+import {WorkspaceDragSurfaceSvg} from './workspace_drag_surface_svg';
+import {WorkspaceDragger} from './workspace_dragger';
+import {resizeSvgContents as realResizeSvgContents, WorkspaceSvg} from './workspace_svg';
+import * as Xml from './xml';
+import {ZoomControls} from './zoom_controls';
 
 
 /**
diff --git a/core/blockly_options.ts b/core/blockly_options.ts
index 775669f92..927a79ada 100644
--- a/core/blockly_options.ts
+++ b/core/blockly_options.ts
@@ -12,7 +12,7 @@
  * Object that defines user-specified options for the workspace.
  * @namespace Blockly.BlocklyOptions
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.BlocklyOptions');
 
 
diff --git a/core/blocks.ts b/core/blocks.ts
index c57e5a8bd..07037bf3a 100644
--- a/core/blocks.ts
+++ b/core/blocks.ts
@@ -12,7 +12,7 @@
  * A mapping of block type names to block prototype objects.
  * @namespace Blockly.blocks
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.blocks');
 
 
diff --git a/core/browser_events.ts b/core/browser_events.ts
index 00d275ba3..432eb0e1c 100644
--- a/core/browser_events.ts
+++ b/core/browser_events.ts
@@ -12,11 +12,11 @@
  * Browser event handling.
  * @namespace Blockly.browserEvents
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.browserEvents');
 
-import * as Touch from './touch.js';
-import * as userAgent from './utils/useragent.js';
+import * as Touch from './touch';
+import * as userAgent from './utils/useragent';
 
 
 /**
diff --git a/core/bubble.ts b/core/bubble.ts
index 29dcb798e..abea01e70 100644
--- a/core/bubble.ts
+++ b/core/bubble.ts
@@ -12,33 +12,33 @@
  * Object representing a UI bubble.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Bubble');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './metrics_manager.js';
+import './metrics_manager';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './workspace.js';
+import './workspace';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockDragSurfaceSvg} from './block_drag_surface.js';
+import {BlockDragSurfaceSvg} from './block_drag_surface';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
 /* eslint-disable-next-line no-unused-vars */
-import {IBubble} from './interfaces/i_bubble.js';
-import {ContainerRegion} from './metrics_manager.js';
-import {Scrollbar} from './scrollbar.js';
-import * as Touch from './touch.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import * as math from './utils/math.js';
-import {Size} from './utils/size.js';
-import {Svg} from './utils/svg.js';
-import * as userAgent from './utils/useragent.js';
+import {IBubble} from './interfaces/i_bubble';
+import {ContainerRegion} from './metrics_manager';
+import {Scrollbar} from './scrollbar';
+import * as Touch from './touch';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import * as math from './utils/math';
+import {Size} from './utils/size';
+import {Svg} from './utils/svg';
+import * as userAgent from './utils/useragent';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/bubble_dragger.ts b/core/bubble_dragger.ts
index 297bc4fa4..e91907515 100644
--- a/core/bubble_dragger.ts
+++ b/core/bubble_dragger.ts
@@ -12,31 +12,31 @@
  * Methods for dragging a bubble visually.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.BubbleDragger');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './bubble.js';
+import './bubble';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './constants.js';
+import './constants';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockDragSurfaceSvg} from './block_drag_surface.js';
-import {ComponentManager} from './component_manager.js';
+import {BlockDragSurfaceSvg} from './block_drag_surface';
+import {ComponentManager} from './component_manager';
 /* eslint-disable-next-line no-unused-vars */
-import {CommentMove} from './events/events_comment_move.js';
-import * as eventUtils from './events/utils.js';
+import {CommentMove} from './events/events_comment_move';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {IBubble} from './interfaces/i_bubble.js';
+import {IBubble} from './interfaces/i_bubble';
 /* eslint-disable-next-line no-unused-vars */
-import {IDeleteArea} from './interfaces/i_delete_area.js';
+import {IDeleteArea} from './interfaces/i_delete_area';
 /* eslint-disable-next-line no-unused-vars */
-import {IDragTarget} from './interfaces/i_drag_target.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as svgMath from './utils/svg_math.js';
-import {WorkspaceCommentSvg} from './workspace_comment_svg.js';
+import {IDragTarget} from './interfaces/i_drag_target';
+import {Coordinate} from './utils/coordinate';
+import * as svgMath from './utils/svg_math';
+import {WorkspaceCommentSvg} from './workspace_comment_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/bump_objects.ts b/core/bump_objects.ts
index 29a08b4cc..e83a18eb6 100644
--- a/core/bump_objects.ts
+++ b/core/bump_objects.ts
@@ -12,28 +12,28 @@
  * Utilities for bumping objects back into worksapce bounds.
  * @namespace Blockly.bumpObjects
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.bumpObjects');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
+import {BlockSvg} from './block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {Abstract} from './events/events_abstract.js';
-import {BlockCreate} from './events/events_block_create.js';
-import {BlockMove} from './events/events_block_move.js';
-import {CommentCreate} from './events/events_comment_create.js';
-import {CommentMove} from './events/events_comment_move.js';
+import {Abstract} from './events/events_abstract';
+import {BlockCreate} from './events/events_block_create';
+import {BlockMove} from './events/events_block_move';
+import {CommentCreate} from './events/events_comment_create';
+import {CommentMove} from './events/events_comment_move';
 /* eslint-disable-next-line no-unused-vars */
-import {ViewportChange} from './events/events_viewport.js';
-import * as eventUtils from './events/utils.js';
+import {ViewportChange} from './events/events_viewport';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {IBoundedElement} from './interfaces/i_bounded_element.js';
-import {ContainerRegion, MetricsManager} from './metrics_manager.js';
-import * as mathUtils from './utils/math.js';
+import {IBoundedElement} from './interfaces/i_bounded_element';
+import {ContainerRegion, MetricsManager} from './metrics_manager';
+import * as mathUtils from './utils/math';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceCommentSvg} from './workspace_comment_svg.js';
+import {WorkspaceCommentSvg} from './workspace_comment_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/clipboard.ts b/core/clipboard.ts
index 2788f90ed..36203e777 100644
--- a/core/clipboard.ts
+++ b/core/clipboard.ts
@@ -12,10 +12,10 @@
  * Blockly's internal clipboard for managing copy-paste.
  * @namespace Blockly.clipboard
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.clipboard');
 
-import {CopyData, ICopyable} from './interfaces/i_copyable.js';
+import {CopyData, ICopyable} from './interfaces/i_copyable';
 
 
 /** Metadata about the object that is currently on the clipboard. */
diff --git a/core/comment.ts b/core/comment.ts
index 3941f7531..51b44f06c 100644
--- a/core/comment.ts
+++ b/core/comment.ts
@@ -12,37 +12,37 @@
  * Object representing a code comment.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Comment');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './block.js';
+import './block';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './workspace_svg.js';
+import './workspace_svg';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_change.js';
+import './events/events_block_change';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_bubble_open.js';
+import './events/events_bubble_open';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './warning.js';
+import './warning';
 
-import {CommentModel} from './block.js';
+import {CommentModel} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
-import {Bubble} from './bubble.js';
-import * as Css from './css.js';
-import * as eventUtils from './events/utils.js';
-import {Icon} from './icon.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
+import {Bubble} from './bubble';
+import * as Css from './css';
+import * as eventUtils from './events/utils';
+import {Icon} from './icon';
 /* eslint-disable-next-line no-unused-vars */
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
 /* eslint-disable-next-line no-unused-vars */
-import {Size} from './utils/size.js';
-import {Svg} from './utils/svg.js';
-import * as userAgent from './utils/useragent.js';
+import {Size} from './utils/size';
+import {Svg} from './utils/svg';
+import * as userAgent from './utils/useragent';
 
 
 /**
diff --git a/core/common.ts b/core/common.ts
index edbf2a6fb..008a7c218 100644
--- a/core/common.ts
+++ b/core/common.ts
@@ -14,21 +14,21 @@
  * must not be at the top level to avoid circular dependencies.
  * @namespace Blockly.common
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.common');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
-import {BlockDefinition, Blocks} from './blocks.js';
+import {Block} from './block';
+import {BlockDefinition, Blocks} from './blocks';
 /* eslint-disable-next-line no-unused-vars */
-import {Connection} from './connection.js';
+import {Connection} from './connection';
 /* eslint-disable-next-line no-unused-vars */
-import {ICopyable} from './interfaces/i_copyable.js';
+import {ICopyable} from './interfaces/i_copyable';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/component_manager.ts b/core/component_manager.ts
index a39130a47..9dcf6e8aa 100644
--- a/core/component_manager.ts
+++ b/core/component_manager.ts
@@ -12,20 +12,20 @@
  * Manager for all items registered with the workspace.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ComponentManager');
 
 /* eslint-disable-next-line no-unused-vars */
-import {IAutoHideable} from './interfaces/i_autohideable.js';
+import {IAutoHideable} from './interfaces/i_autohideable';
 /* eslint-disable-next-line no-unused-vars */
-import {IComponent} from './interfaces/i_component.js';
+import {IComponent} from './interfaces/i_component';
 /* eslint-disable-next-line no-unused-vars */
-import {IDeleteArea} from './interfaces/i_delete_area.js';
+import {IDeleteArea} from './interfaces/i_delete_area';
 /* eslint-disable-next-line no-unused-vars */
-import {IDragTarget} from './interfaces/i_drag_target.js';
+import {IDragTarget} from './interfaces/i_drag_target';
 /* eslint-disable-next-line no-unused-vars */
-import {IPositionable} from './interfaces/i_positionable.js';
-import * as arrayUtils from './utils/array.js';
+import {IPositionable} from './interfaces/i_positionable';
+import * as arrayUtils from './utils/array';
 
 
 class Capability<T> {
diff --git a/core/config.ts b/core/config.ts
index 64f10199c..9aec22ba0 100644
--- a/core/config.ts
+++ b/core/config.ts
@@ -16,7 +16,7 @@
  * generally recommended.
  * @namespace Blockly.config
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.config');
 
 
diff --git a/core/connection.ts b/core/connection.ts
index 3899f441f..66d65b6f6 100644
--- a/core/connection.ts
+++ b/core/connection.ts
@@ -12,26 +12,26 @@
  * Components for creating connections between blocks.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Connection');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './constants.js';
+import './constants';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
-import {ConnectionType} from './connection_type.js';
+import {Block} from './block';
+import {ConnectionType} from './connection_type';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockMove} from './events/events_block_move.js';
-import * as eventUtils from './events/utils.js';
+import {BlockMove} from './events/events_block_move';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from './input.js';
+import {Input} from './input';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocationWithBlock} from './interfaces/i_ast_node_location_with_block.js';
+import {IASTNodeLocationWithBlock} from './interfaces/i_ast_node_location_with_block';
 /* eslint-disable-next-line no-unused-vars */
-import {IConnectionChecker} from './interfaces/i_connection_checker.js';
-import * as blocks from './serialization/blocks.js';
-import * as Xml from './xml.js';
+import {IConnectionChecker} from './interfaces/i_connection_checker';
+import * as blocks from './serialization/blocks';
+import * as Xml from './xml';
 
 
 /**
diff --git a/core/connection_checker.ts b/core/connection_checker.ts
index 9b07b30d5..e1f117794 100644
--- a/core/connection_checker.ts
+++ b/core/connection_checker.ts
@@ -14,18 +14,18 @@
  * potential connection is safe and valid.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ConnectionChecker');
 
-import * as common from './common.js';
-import {Connection} from './connection.js';
-import {ConnectionType} from './connection_type.js';
+import * as common from './common';
+import {Connection} from './connection';
+import {ConnectionType} from './connection_type';
 /* eslint-disable-next-line no-unused-vars */
-import {IConnectionChecker} from './interfaces/i_connection_checker.js';
-import * as internalConstants from './internal_constants.js';
-import * as registry from './registry.js';
+import {IConnectionChecker} from './interfaces/i_connection_checker';
+import * as internalConstants from './internal_constants';
+import * as registry from './registry';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from './rendered_connection.js';
+import {RenderedConnection} from './rendered_connection';
 
 
 /**
diff --git a/core/connection_db.ts b/core/connection_db.ts
index eb8c489e8..d9f027320 100644
--- a/core/connection_db.ts
+++ b/core/connection_db.ts
@@ -16,19 +16,19 @@
  *    Sorted by y coordinate.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ConnectionDB');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './constants.js';
+import './constants';
 
-import {ConnectionType} from './connection_type.js';
+import {ConnectionType} from './connection_type';
 /* eslint-disable-next-line no-unused-vars */
-import {IConnectionChecker} from './interfaces/i_connection_checker.js';
+import {IConnectionChecker} from './interfaces/i_connection_checker';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from './rendered_connection.js';
+import {RenderedConnection} from './rendered_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {Coordinate} from './utils/coordinate.js';
+import {Coordinate} from './utils/coordinate';
 
 
 /**
diff --git a/core/connection_type.ts b/core/connection_type.ts
index 337fa225c..aa7fe1879 100644
--- a/core/connection_type.ts
+++ b/core/connection_type.ts
@@ -12,7 +12,7 @@
  * An enum for the possible types of connections.
  * @namespace Blockly.ConnectionType
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ConnectionType');
 
 
diff --git a/core/constants.ts b/core/constants.ts
index 15f08f077..8ea419bda 100644
--- a/core/constants.ts
+++ b/core/constants.ts
@@ -12,7 +12,7 @@
  * Blockly constants.
  * @namespace Blockly.constants
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.constants');
 
 
diff --git a/core/contextmenu.ts b/core/contextmenu.ts
index f432ad4fd..c3592cfb1 100644
--- a/core/contextmenu.ts
+++ b/core/contextmenu.ts
@@ -12,33 +12,33 @@
  * Functionality for the right-click context menus.
  * @namespace Blockly.ContextMenu
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ContextMenu');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
-import * as clipboard from './clipboard.js';
-import {config} from './config.js';
-import {ContextMenuOption, ContextMenuRegistry, LegacyContextMenuOption} from './contextmenu_registry.js';
-import * as BlockCreate from './events/events_block_create.js';
-import * as eventUtils from './events/utils.js';
-import {Menu} from './menu.js';
-import {MenuItem} from './menuitem.js';
-import {Msg} from './msg.js';
-import * as aria from './utils/aria.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {Rect} from './utils/rect.js';
-import * as svgMath from './utils/svg_math.js';
-import * as userAgent from './utils/useragent.js';
-import * as WidgetDiv from './widgetdiv.js';
-import {WorkspaceCommentSvg} from './workspace_comment_svg.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
+import * as clipboard from './clipboard';
+import {config} from './config';
+import {ContextMenuOption, ContextMenuRegistry, LegacyContextMenuOption} from './contextmenu_registry';
+import * as BlockCreate from './events/events_block_create';
+import * as eventUtils from './events/utils';
+import {Menu} from './menu';
+import {MenuItem} from './menuitem';
+import {Msg} from './msg';
+import * as aria from './utils/aria';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {Rect} from './utils/rect';
+import * as svgMath from './utils/svg_math';
+import * as userAgent from './utils/useragent';
+import * as WidgetDiv from './widgetdiv';
+import {WorkspaceCommentSvg} from './workspace_comment_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
-import * as Xml from './xml.js';
+import {WorkspaceSvg} from './workspace_svg';
+import * as Xml from './xml';
 
 
 /**
diff --git a/core/contextmenu_items.ts b/core/contextmenu_items.ts
index 6d840ab41..d84495064 100644
--- a/core/contextmenu_items.ts
+++ b/core/contextmenu_items.ts
@@ -12,22 +12,22 @@
  * Registers default context menu items.
  * @namespace Blockly.ContextMenuItems
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ContextMenuItems');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as clipboard from './clipboard.js';
-import {ContextMenuRegistry, RegistryItem, Scope} from './contextmenu_registry.js';
-import * as dialog from './dialog.js';
-import * as Events from './events/events.js';
-import * as eventUtils from './events/utils.js';
-import {inputTypes} from './input_types.js';
-import {Msg} from './msg.js';
-import * as idGenerator from './utils/idgenerator.js';
-import * as userAgent from './utils/useragent.js';
+import {BlockSvg} from './block_svg';
+import * as clipboard from './clipboard';
+import {ContextMenuRegistry, RegistryItem, Scope} from './contextmenu_registry';
+import * as dialog from './dialog';
+import * as Events from './events/events';
+import * as eventUtils from './events/utils';
+import {inputTypes} from './input_types';
+import {Msg} from './msg';
+import * as idGenerator from './utils/idgenerator';
+import * as userAgent from './utils/useragent';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/contextmenu_registry.ts b/core/contextmenu_registry.ts
index a3fa6aba0..6ea906243 100644
--- a/core/contextmenu_registry.ts
+++ b/core/contextmenu_registry.ts
@@ -12,13 +12,13 @@
  * Registry for context menu option items.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ContextMenuRegistry');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
+import {BlockSvg} from './block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/css.ts b/core/css.ts
index 02300946c..ec83ef6bb 100644
--- a/core/css.ts
+++ b/core/css.ts
@@ -12,10 +12,10 @@
  * Inject Blockly's CSS synchronously.
  * @namespace Blockly.Css
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Css');
 
-import * as deprecation from './utils/deprecation.js';
+import * as deprecation from './utils/deprecation';
 
 
 /** Has CSS already been injected? */
diff --git a/core/delete_area.ts b/core/delete_area.ts
index da7870745..c6f5449bd 100644
--- a/core/delete_area.ts
+++ b/core/delete_area.ts
@@ -14,15 +14,15 @@
  * bubble that is dropped on top of it.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.DeleteArea');
 
-import {BlockSvg} from './block_svg.js';
-import {DragTarget} from './drag_target.js';
+import {BlockSvg} from './block_svg';
+import {DragTarget} from './drag_target';
 /* eslint-disable-next-line no-unused-vars */
-import {IDeleteArea} from './interfaces/i_delete_area.js';
+import {IDeleteArea} from './interfaces/i_delete_area';
 /* eslint-disable-next-line no-unused-vars */
-import {IDraggable} from './interfaces/i_draggable.js';
+import {IDraggable} from './interfaces/i_draggable';
 
 
 /**
diff --git a/core/dialog.ts b/core/dialog.ts
index f839cfba3..87dbe326d 100644
--- a/core/dialog.ts
+++ b/core/dialog.ts
@@ -13,7 +13,7 @@
  * Wrapper functions around JS functions for showing alert/confirmation dialogs.
  * @namespace Blockly.dialog
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.dialog');
 
 
diff --git a/core/drag_target.ts b/core/drag_target.ts
index 8f2178302..71099e85c 100644
--- a/core/drag_target.ts
+++ b/core/drag_target.ts
@@ -14,15 +14,15 @@
  * block or bubble is dragged over or dropped on top of it.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.DragTarget');
 
 /* eslint-disable-next-line no-unused-vars */
-import {IDragTarget} from './interfaces/i_drag_target.js';
+import {IDragTarget} from './interfaces/i_drag_target';
 /* eslint-disable-next-line no-unused-vars */
-import {IDraggable} from './interfaces/i_draggable.js';
+import {IDraggable} from './interfaces/i_draggable';
 /* eslint-disable-next-line no-unused-vars */
-import {Rect} from './utils/rect.js';
+import {Rect} from './utils/rect';
 
 
 /**
diff --git a/core/dropdowndiv.ts b/core/dropdowndiv.ts
index 13dd961a7..c5e0a75d9 100644
--- a/core/dropdowndiv.ts
+++ b/core/dropdowndiv.ts
@@ -14,22 +14,22 @@
  * A div that floats on top of the workspace, for drop-down menus.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.dropDownDiv');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as common from './common.js';
+import {BlockSvg} from './block_svg';
+import * as common from './common';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from './field.js';
-import * as dom from './utils/dom.js';
-import * as math from './utils/math.js';
-import {Rect} from './utils/rect.js';
+import {Field} from './field';
+import * as dom from './utils/dom';
+import * as math from './utils/math';
+import {Rect} from './utils/rect';
 /* eslint-disable-next-line no-unused-vars */
-import {Size} from './utils/size.js';
-import * as style from './utils/style.js';
+import {Size} from './utils/size';
+import * as style from './utils/style';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/events/events.ts b/core/events/events.ts
index c3a7722e7..4dbd090d4 100644
--- a/core/events/events.ts
+++ b/core/events/events.ts
@@ -12,37 +12,37 @@
  * Events fired as a result of actions in Blockly's editor.
  * @namespace Blockly.Events
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events');
 
-import {Abstract as AbstractEvent} from './events_abstract.js';
-import {BlockBase} from './events_block_base.js';
-import {BlockChange} from './events_block_change.js';
-import {BlockCreate} from './events_block_create.js';
-import {BlockDelete} from './events_block_delete.js';
-import {BlockDrag} from './events_block_drag.js';
-import {BlockMove} from './events_block_move.js';
-import {BubbleOpen} from './events_bubble_open.js';
-import {Click} from './events_click.js';
-import {CommentBase} from './events_comment_base.js';
-import {CommentChange} from './events_comment_change.js';
-import {CommentCreate} from './events_comment_create.js';
-import {CommentDelete} from './events_comment_delete.js';
-import {CommentMove} from './events_comment_move.js';
-import {MarkerMove} from './events_marker_move.js';
-import {Selected} from './events_selected.js';
-import {ThemeChange} from './events_theme_change.js';
-import {ToolboxItemSelect} from './events_toolbox_item_select.js';
-import {TrashcanOpen} from './events_trashcan_open.js';
-import {Ui} from './events_ui.js';
-import {UiBase} from './events_ui_base.js';
-import {VarBase} from './events_var_base.js';
-import {VarCreate} from './events_var_create.js';
-import {VarDelete} from './events_var_delete.js';
-import {VarRename} from './events_var_rename.js';
-import {ViewportChange} from './events_viewport.js';
-import * as eventUtils from './utils.js';
-import {FinishedLoading} from './workspace_events.js';
+import {Abstract as AbstractEvent} from './events_abstract';
+import {BlockBase} from './events_block_base';
+import {BlockChange} from './events_block_change';
+import {BlockCreate} from './events_block_create';
+import {BlockDelete} from './events_block_delete';
+import {BlockDrag} from './events_block_drag';
+import {BlockMove} from './events_block_move';
+import {BubbleOpen} from './events_bubble_open';
+import {Click} from './events_click';
+import {CommentBase} from './events_comment_base';
+import {CommentChange} from './events_comment_change';
+import {CommentCreate} from './events_comment_create';
+import {CommentDelete} from './events_comment_delete';
+import {CommentMove} from './events_comment_move';
+import {MarkerMove} from './events_marker_move';
+import {Selected} from './events_selected';
+import {ThemeChange} from './events_theme_change';
+import {ToolboxItemSelect} from './events_toolbox_item_select';
+import {TrashcanOpen} from './events_trashcan_open';
+import {Ui} from './events_ui';
+import {UiBase} from './events_ui_base';
+import {VarBase} from './events_var_base';
+import {VarCreate} from './events_var_create';
+import {VarDelete} from './events_var_delete';
+import {VarRename} from './events_var_rename';
+import {ViewportChange} from './events_viewport';
+import * as eventUtils from './utils';
+import {FinishedLoading} from './workspace_events';
 
 
 // Events.
diff --git a/core/events/events_abstract.ts b/core/events/events_abstract.ts
index 36faea962..969325bb9 100644
--- a/core/events/events_abstract.ts
+++ b/core/events/events_abstract.ts
@@ -14,13 +14,13 @@
  * Blockly's editor.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.Abstract');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from '../workspace.js';
+import {Workspace} from '../workspace';
 
-import * as eventUtils from './utils.js';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_block_base.ts b/core/events/events_block_base.ts
index af0484d5b..ee0ff25bd 100644
--- a/core/events/events_block_base.ts
+++ b/core/events/events_block_base.ts
@@ -12,13 +12,13 @@
  * Base class for all types of block events.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.BlockBase');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
+import {Block} from '../block';
 
-import {Abstract as AbstractEvent} from './events_abstract.js';
+import {Abstract as AbstractEvent} from './events_abstract';
 
 
 /**
diff --git a/core/events/events_block_change.ts b/core/events/events_block_change.ts
index 95e197fd7..8fa5a0fb8 100644
--- a/core/events/events_block_change.ts
+++ b/core/events/events_block_change.ts
@@ -12,18 +12,18 @@
  * Class for a block change event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.BlockChange');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
+import {Block} from '../block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../block_svg.js';
-import * as registry from '../registry.js';
-import * as Xml from '../xml.js';
+import {BlockSvg} from '../block_svg';
+import * as registry from '../registry';
+import * as Xml from '../xml';
 
-import {BlockBase} from './events_block_base.js';
-import * as eventUtils from './utils.js';
+import {BlockBase} from './events_block_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_block_create.ts b/core/events/events_block_create.ts
index 02f27ab02..018736d46 100644
--- a/core/events/events_block_create.ts
+++ b/core/events/events_block_create.ts
@@ -12,17 +12,17 @@
  * Class for a block creation event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.BlockCreate');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
-import * as registry from '../registry.js';
-import * as blocks from '../serialization/blocks.js';
-import * as Xml from '../xml.js';
+import {Block} from '../block';
+import * as registry from '../registry';
+import * as blocks from '../serialization/blocks';
+import * as Xml from '../xml';
 
-import {BlockBase} from './events_block_base.js';
-import * as eventUtils from './utils.js';
+import {BlockBase} from './events_block_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_block_delete.ts b/core/events/events_block_delete.ts
index 5823a9ec2..296a58b94 100644
--- a/core/events/events_block_delete.ts
+++ b/core/events/events_block_delete.ts
@@ -12,17 +12,17 @@
  * Class for a block delete event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.BlockDelete');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
-import * as registry from '../registry.js';
-import * as blocks from '../serialization/blocks.js';
-import * as Xml from '../xml.js';
+import {Block} from '../block';
+import * as registry from '../registry';
+import * as blocks from '../serialization/blocks';
+import * as Xml from '../xml';
 
-import {BlockBase} from './events_block_base.js';
-import * as eventUtils from './utils.js';
+import {BlockBase} from './events_block_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_block_drag.ts b/core/events/events_block_drag.ts
index 2ddf87cbf..c6ef42125 100644
--- a/core/events/events_block_drag.ts
+++ b/core/events/events_block_drag.ts
@@ -12,15 +12,15 @@
  * Events fired as a block drag.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.BlockDrag');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
-import * as registry from '../registry.js';
+import {Block} from '../block';
+import * as registry from '../registry';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_block_move.ts b/core/events/events_block_move.ts
index c9621d29c..00eef2f4c 100644
--- a/core/events/events_block_move.ts
+++ b/core/events/events_block_move.ts
@@ -12,17 +12,17 @@
  * Class for a block move event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.BlockMove');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
-import {ConnectionType} from '../connection_type.js';
-import * as registry from '../registry.js';
-import {Coordinate} from '../utils/coordinate.js';
+import {Block} from '../block';
+import {ConnectionType} from '../connection_type';
+import * as registry from '../registry';
+import {Coordinate} from '../utils/coordinate';
 
-import {BlockBase} from './events_block_base.js';
-import * as eventUtils from './utils.js';
+import {BlockBase} from './events_block_base';
+import * as eventUtils from './utils';
 
 
 interface BlockLocation {
diff --git a/core/events/events_bubble_open.ts b/core/events/events_bubble_open.ts
index 4f7bcda11..7171a2b73 100644
--- a/core/events/events_bubble_open.ts
+++ b/core/events/events_bubble_open.ts
@@ -12,15 +12,15 @@
  * Events fired as a result of bubble open.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.BubbleOpen');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../block_svg.js';
-import * as registry from '../registry.js';
+import {BlockSvg} from '../block_svg';
+import * as registry from '../registry';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_click.ts b/core/events/events_click.ts
index e92900324..382ed1990 100644
--- a/core/events/events_click.ts
+++ b/core/events/events_click.ts
@@ -12,15 +12,15 @@
  * Events fired as a result of UI click in Blockly's editor.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.Click');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
-import * as registry from '../registry.js';
+import {Block} from '../block';
+import * as registry from '../registry';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_comment_base.ts b/core/events/events_comment_base.ts
index 54f4d93c8..706b788b7 100644
--- a/core/events/events_comment_base.ts
+++ b/core/events/events_comment_base.ts
@@ -12,20 +12,20 @@
  * Base class for comment events.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.CommentBase');
 
-import * as utilsXml from '../utils/xml.js';
+import * as utilsXml from '../utils/xml';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceComment} from '../workspace_comment.js';
-import * as Xml from '../xml.js';
+import {WorkspaceComment} from '../workspace_comment';
+import * as Xml from '../xml';
 
-import {Abstract as AbstractEvent} from './events_abstract.js';
+import {Abstract as AbstractEvent} from './events_abstract';
 /* eslint-disable-next-line no-unused-vars */
-import {CommentCreate} from './events_comment_create.js';
+import {CommentCreate} from './events_comment_create';
 /* eslint-disable-next-line no-unused-vars */
-import {CommentDelete} from './events_comment_delete.js';
-import * as eventUtils from './utils.js';
+import {CommentDelete} from './events_comment_delete';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_comment_change.ts b/core/events/events_comment_change.ts
index 4553fcf44..78e1ddce9 100644
--- a/core/events/events_comment_change.ts
+++ b/core/events/events_comment_change.ts
@@ -12,15 +12,15 @@
  * Class for comment change event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.CommentChange');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceComment} from '../workspace_comment.js';
+import {WorkspaceComment} from '../workspace_comment';
 
-import {CommentBase} from './events_comment_base.js';
-import * as eventUtils from './utils.js';
+import {CommentBase} from './events_comment_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_comment_create.ts b/core/events/events_comment_create.ts
index 6afc6cb50..f642e308e 100644
--- a/core/events/events_comment_create.ts
+++ b/core/events/events_comment_create.ts
@@ -12,16 +12,16 @@
  * Class for comment creation event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.CommentCreate');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceComment} from '../workspace_comment.js';
-import * as Xml from '../xml.js';
+import {WorkspaceComment} from '../workspace_comment';
+import * as Xml from '../xml';
 
-import {CommentBase} from './events_comment_base.js';
-import * as eventUtils from './utils.js';
+import {CommentBase} from './events_comment_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_comment_delete.ts b/core/events/events_comment_delete.ts
index 1293ec8d6..92a33d0c4 100644
--- a/core/events/events_comment_delete.ts
+++ b/core/events/events_comment_delete.ts
@@ -12,15 +12,15 @@
  * Class for comment deletion event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.CommentDelete');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceComment} from '../workspace_comment.js';
+import {WorkspaceComment} from '../workspace_comment';
 
-import {CommentBase} from './events_comment_base.js';
-import * as eventUtils from './utils.js';
+import {CommentBase} from './events_comment_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_comment_move.ts b/core/events/events_comment_move.ts
index 3a69f8dd5..522b1473d 100644
--- a/core/events/events_comment_move.ts
+++ b/core/events/events_comment_move.ts
@@ -12,16 +12,16 @@
  * Class for comment move event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.CommentMove');
 
-import * as registry from '../registry.js';
-import {Coordinate} from '../utils/coordinate.js';
+import * as registry from '../registry';
+import {Coordinate} from '../utils/coordinate';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceComment} from '../workspace_comment.js';
+import {WorkspaceComment} from '../workspace_comment';
 
-import {CommentBase} from './events_comment_base.js';
-import * as eventUtils from './utils.js';
+import {CommentBase} from './events_comment_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_marker_move.ts b/core/events/events_marker_move.ts
index 1ebc9e6fb..8751d2032 100644
--- a/core/events/events_marker_move.ts
+++ b/core/events/events_marker_move.ts
@@ -12,18 +12,18 @@
  * Events fired as a result of a marker move.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.MarkerMove');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
-import {ASTNode} from '../keyboard_nav/ast_node.js';
-import * as registry from '../registry.js';
+import {Block} from '../block';
+import {ASTNode} from '../keyboard_nav/ast_node';
+import * as registry from '../registry';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from '../workspace.js';
+import {Workspace} from '../workspace';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_selected.ts b/core/events/events_selected.ts
index 3034af1a5..8d7502337 100644
--- a/core/events/events_selected.ts
+++ b/core/events/events_selected.ts
@@ -12,13 +12,13 @@
  * Events fired as a result of element select action.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.Selected');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_theme_change.ts b/core/events/events_theme_change.ts
index c3648a2a4..988fa1889 100644
--- a/core/events/events_theme_change.ts
+++ b/core/events/events_theme_change.ts
@@ -12,13 +12,13 @@
  * Events fired as a result of a theme update.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.ThemeChange');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_toolbox_item_select.ts b/core/events/events_toolbox_item_select.ts
index db6c3b2eb..a854d7969 100644
--- a/core/events/events_toolbox_item_select.ts
+++ b/core/events/events_toolbox_item_select.ts
@@ -12,13 +12,13 @@
  * Events fired as a result of selecting an item on the toolbox.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.ToolboxItemSelect');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_trashcan_open.ts b/core/events/events_trashcan_open.ts
index 0940517f5..2cac5ea5e 100644
--- a/core/events/events_trashcan_open.ts
+++ b/core/events/events_trashcan_open.ts
@@ -12,13 +12,13 @@
  * Events fired as a result of trashcan flyout open and close.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.TrashcanOpen');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_ui.ts b/core/events/events_ui.ts
index d667bc114..a95857ae3 100644
--- a/core/events/events_ui.ts
+++ b/core/events/events_ui.ts
@@ -14,15 +14,15 @@
  * Blockly's editor.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.Ui');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
-import * as registry from '../registry.js';
+import {Block} from '../block';
+import * as registry from '../registry';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_ui_base.ts b/core/events/events_ui_base.ts
index 8f9c2fd3d..34e368812 100644
--- a/core/events/events_ui_base.ts
+++ b/core/events/events_ui_base.ts
@@ -14,10 +14,10 @@
  * Blockly's editor.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.UiBase');
 
-import {Abstract as AbstractEvent} from './events_abstract.js';
+import {Abstract as AbstractEvent} from './events_abstract';
 
 
 /**
diff --git a/core/events/events_var_base.ts b/core/events/events_var_base.ts
index 70b4d131c..c6671e721 100644
--- a/core/events/events_var_base.ts
+++ b/core/events/events_var_base.ts
@@ -12,13 +12,13 @@
  * Abstract class for a variable event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.VarBase');
 
 /* eslint-disable-next-line no-unused-vars */
-import {VariableModel} from '../variable_model.js';
+import {VariableModel} from '../variable_model';
 
-import {Abstract as AbstractEvent} from './events_abstract.js';
+import {Abstract as AbstractEvent} from './events_abstract';
 
 
 /**
diff --git a/core/events/events_var_create.ts b/core/events/events_var_create.ts
index c8ce8fe8a..07ce98d02 100644
--- a/core/events/events_var_create.ts
+++ b/core/events/events_var_create.ts
@@ -12,15 +12,15 @@
  * Class for a variable creation event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.VarCreate');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 /* eslint-disable-next-line no-unused-vars */
-import {VariableModel} from '../variable_model.js';
+import {VariableModel} from '../variable_model';
 
-import {VarBase} from './events_var_base.js';
-import * as eventUtils from './utils.js';
+import {VarBase} from './events_var_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_var_delete.ts b/core/events/events_var_delete.ts
index 5fd30f66f..15eab9aff 100644
--- a/core/events/events_var_delete.ts
+++ b/core/events/events_var_delete.ts
@@ -12,15 +12,15 @@
  * Classes for all types of variable events.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.VarDelete');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 /* eslint-disable-next-line no-unused-vars */
-import {VariableModel} from '../variable_model.js';
+import {VariableModel} from '../variable_model';
 
-import {VarBase} from './events_var_base.js';
-import * as eventUtils from './utils.js';
+import {VarBase} from './events_var_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_var_rename.ts b/core/events/events_var_rename.ts
index 4fefd49ef..9c02b4dfb 100644
--- a/core/events/events_var_rename.ts
+++ b/core/events/events_var_rename.ts
@@ -12,15 +12,15 @@
  * Class for a variable rename event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.VarRename');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 /* eslint-disable-next-line no-unused-vars */
-import {VariableModel} from '../variable_model.js';
+import {VariableModel} from '../variable_model';
 
-import {VarBase} from './events_var_base.js';
-import * as eventUtils from './utils.js';
+import {VarBase} from './events_var_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/events_viewport.ts b/core/events/events_viewport.ts
index 45609717b..5b9690c8e 100644
--- a/core/events/events_viewport.ts
+++ b/core/events/events_viewport.ts
@@ -12,13 +12,13 @@
  * Events fired as a result of a viewport change.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.ViewportChange');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 
-import {UiBase} from './events_ui_base.js';
-import * as eventUtils from './utils.js';
+import {UiBase} from './events_ui_base';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/events/utils.ts b/core/events/utils.ts
index 6f41cf67f..9f65abc2d 100644
--- a/core/events/utils.ts
+++ b/core/events/utils.ts
@@ -14,32 +14,32 @@
  * actions in Blockly's editor.
  * @namespace Blockly.Events.utils
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.utils');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
-import * as registry from '../registry.js';
-import * as idGenerator from '../utils/idgenerator.js';
+import {Block} from '../block';
+import * as registry from '../registry';
+import * as idGenerator from '../utils/idgenerator';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from '../workspace.js';
+import {Workspace} from '../workspace';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../workspace_svg.js';
+import {WorkspaceSvg} from '../workspace_svg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Abstract} from './events_abstract.js';
+import {Abstract} from './events_abstract';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockChange} from './events_block_change.js';
+import {BlockChange} from './events_block_change';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockCreate} from './events_block_create.js';
+import {BlockCreate} from './events_block_create';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockMove} from './events_block_move.js';
+import {BlockMove} from './events_block_move';
 /* eslint-disable-next-line no-unused-vars */
-import {CommentCreate} from './events_comment_create.js';
+import {CommentCreate} from './events_comment_create';
 /* eslint-disable-next-line no-unused-vars */
-import {CommentMove} from './events_comment_move.js';
+import {CommentMove} from './events_comment_move';
 /* eslint-disable-next-line no-unused-vars */
-import {ViewportChange} from './events_viewport.js';
+import {ViewportChange} from './events_viewport';
 
 
 /** Group ID for new events.  Grouped events are indivisible. */
diff --git a/core/events/workspace_events.ts b/core/events/workspace_events.ts
index 643b85f68..7f271b539 100644
--- a/core/events/workspace_events.ts
+++ b/core/events/workspace_events.ts
@@ -12,15 +12,15 @@
  * Class for a finished loading workspace event.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Events.FinishedLoading');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from '../workspace.js';
+import {Workspace} from '../workspace';
 
-import {Abstract as AbstractEvent} from './events_abstract.js';
-import * as eventUtils from './utils.js';
+import {Abstract as AbstractEvent} from './events_abstract';
+import * as eventUtils from './utils';
 
 
 /**
diff --git a/core/extensions.ts b/core/extensions.ts
index 1846bd8d1..22122c851 100644
--- a/core/extensions.ts
+++ b/core/extensions.ts
@@ -18,18 +18,18 @@
  *      array attribute.
  * @namespace Blockly.Extensions
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Extensions');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './mutator.js';
+import './mutator';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
-import {BlockSvg} from './block_svg.js';
-import {FieldDropdown} from './field_dropdown.js';
-import {Mutator} from './mutator.js';
-import * as parsing from './utils/parsing.js';
+import {Block} from './block';
+import {BlockSvg} from './block_svg';
+import {FieldDropdown} from './field_dropdown';
+import {Mutator} from './mutator';
+import * as parsing from './utils/parsing';
 
 
 /** The set of all registered extensions, keyed by extension name/id. */
diff --git a/core/field.ts b/core/field.ts
index 728c10558..658f25b5c 100644
--- a/core/field.ts
+++ b/core/field.ts
@@ -16,54 +16,54 @@
  * instances would be FieldTextInput, FieldDropdown, etc.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Field');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './shortcut_registry.js';
+import './shortcut_registry';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_change.js';
+import './events/events_block_change';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './gesture.js';
+import './gesture';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import * as eventUtils from './events/utils.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
+import * as dropDownDiv from './dropdowndiv';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from './input.js';
+import {Input} from './input';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocationSvg} from './interfaces/i_ast_node_location_svg.js';
+import {IASTNodeLocationSvg} from './interfaces/i_ast_node_location_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocationWithBlock} from './interfaces/i_ast_node_location_with_block.js';
+import {IASTNodeLocationWithBlock} from './interfaces/i_ast_node_location_with_block';
 /* eslint-disable-next-line no-unused-vars */
-import {IKeyboardAccessible} from './interfaces/i_keyboard_accessible.js';
+import {IKeyboardAccessible} from './interfaces/i_keyboard_accessible';
 /* eslint-disable-next-line no-unused-vars */
-import {IRegistrable} from './interfaces/i_registrable.js';
-import {MarkerManager} from './marker_manager.js';
+import {IRegistrable} from './interfaces/i_registrable';
+import {MarkerManager} from './marker_manager';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from './renderers/common/constants.js';
-import {KeyboardShortcut} from './shortcut_registry.js';
-import * as Tooltip from './tooltip.js';
+import {ConstantProvider} from './renderers/common/constants';
+import {KeyboardShortcut} from './shortcut_registry';
+import * as Tooltip from './tooltip';
 /* eslint-disable-next-line no-unused-vars */
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import * as parsing from './utils/parsing.js';
-import {Rect} from './utils/rect.js';
-import {Sentinel} from './utils/sentinel.js';
-import {Size} from './utils/size.js';
-import * as style from './utils/style.js';
-import {Svg} from './utils/svg.js';
-import * as userAgent from './utils/useragent.js';
-import * as utilsXml from './utils/xml.js';
-import * as WidgetDiv from './widgetdiv.js';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import * as parsing from './utils/parsing';
+import {Rect} from './utils/rect';
+import {Sentinel} from './utils/sentinel';
+import {Size} from './utils/size';
+import * as style from './utils/style';
+import {Svg} from './utils/svg';
+import * as userAgent from './utils/useragent';
+import * as utilsXml from './utils/xml';
+import * as WidgetDiv from './widgetdiv';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
-import * as Xml from './xml.js';
+import {WorkspaceSvg} from './workspace_svg';
+import * as Xml from './xml';
 
 
 /**
diff --git a/core/field_angle.ts b/core/field_angle.ts
index bd61b0a0a..00a4730d9 100644
--- a/core/field_angle.ts
+++ b/core/field_angle.ts
@@ -12,24 +12,24 @@
  * Angle input field.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldAngle');
 
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
-import * as Css from './css.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import {FieldTextInput} from './field_textinput.js';
-import * as dom from './utils/dom.js';
-import {KeyCodes} from './utils/keycodes.js';
-import * as math from './utils/math.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
+import * as Css from './css';
+import * as dropDownDiv from './dropdowndiv';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import {FieldTextInput} from './field_textinput';
+import * as dom from './utils/dom';
+import {KeyCodes} from './utils/keycodes';
+import * as math from './utils/math';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
-import {Svg} from './utils/svg.js';
-import * as userAgent from './utils/useragent.js';
-import * as WidgetDiv from './widgetdiv.js';
+import {Sentinel} from './utils/sentinel';
+import {Svg} from './utils/svg';
+import * as userAgent from './utils/useragent';
+import * as WidgetDiv from './widgetdiv';
 
 
 /**
diff --git a/core/field_checkbox.ts b/core/field_checkbox.ts
index d254ace14..0558e111f 100644
--- a/core/field_checkbox.ts
+++ b/core/field_checkbox.ts
@@ -12,17 +12,17 @@
  * Checkbox field.  Checked or not checked.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldCheckbox');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_change.js';
+import './events/events_block_change';
 
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import * as dom from './utils/dom.js';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import * as dom from './utils/dom';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
+import {Sentinel} from './utils/sentinel';
 
 
 /**
diff --git a/core/field_colour.ts b/core/field_colour.ts
index 40f260200..8abc3e408 100644
--- a/core/field_colour.ts
+++ b/core/field_colour.ts
@@ -12,26 +12,26 @@
  * Colour input field.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldColour');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_change.js';
+import './events/events_block_change';
 
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
-import * as Css from './css.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import * as aria from './utils/aria.js';
-import * as colour from './utils/colour.js';
-import * as dom from './utils/dom.js';
-import * as idGenerator from './utils/idgenerator.js';
-import {KeyCodes} from './utils/keycodes.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
+import * as Css from './css';
+import * as dropDownDiv from './dropdowndiv';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import * as aria from './utils/aria';
+import * as colour from './utils/colour';
+import * as dom from './utils/dom';
+import * as idGenerator from './utils/idgenerator';
+import {KeyCodes} from './utils/keycodes';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
-import {Size} from './utils/size.js';
+import {Sentinel} from './utils/sentinel';
+import {Size} from './utils/size';
 
 
 /**
diff --git a/core/field_dropdown.ts b/core/field_dropdown.ts
index c759ee325..5e9f5ba81 100644
--- a/core/field_dropdown.ts
+++ b/core/field_dropdown.ts
@@ -16,25 +16,25 @@
  * properties with the context menu.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldDropdown');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import {Menu} from './menu.js';
-import {MenuItem} from './menuitem.js';
-import * as aria from './utils/aria.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import * as parsing from './utils/parsing.js';
+import {BlockSvg} from './block_svg';
+import * as dropDownDiv from './dropdowndiv';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import {Menu} from './menu';
+import {MenuItem} from './menuitem';
+import * as aria from './utils/aria';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import * as parsing from './utils/parsing';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
-import * as utilsString from './utils/string.js';
-import {Svg} from './utils/svg.js';
-import * as userAgent from './utils/useragent.js';
+import {Sentinel} from './utils/sentinel';
+import * as utilsString from './utils/string';
+import {Svg} from './utils/svg';
+import * as userAgent from './utils/useragent';
 
 
 /**
diff --git a/core/field_image.ts b/core/field_image.ts
index 9ff494550..ab86a363a 100644
--- a/core/field_image.ts
+++ b/core/field_image.ts
@@ -12,17 +12,17 @@
  * Image field.  Used for pictures, icons, etc.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldImage');
 
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import * as dom from './utils/dom.js';
-import * as parsing from './utils/parsing.js';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import * as dom from './utils/dom';
+import * as parsing from './utils/parsing';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
-import {Size} from './utils/size.js';
-import {Svg} from './utils/svg.js';
+import {Sentinel} from './utils/sentinel';
+import {Size} from './utils/size';
+import {Svg} from './utils/svg';
 
 
 /**
diff --git a/core/field_label.ts b/core/field_label.ts
index bc47a1505..52cddafb8 100644
--- a/core/field_label.ts
+++ b/core/field_label.ts
@@ -14,15 +14,15 @@
  *    labels, etc.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldLabel');
 
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import * as dom from './utils/dom.js';
-import * as parsing from './utils/parsing.js';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import * as dom from './utils/dom';
+import * as parsing from './utils/parsing';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
+import {Sentinel} from './utils/sentinel';
 
 
 /**
diff --git a/core/field_label_serializable.ts b/core/field_label_serializable.ts
index 51b300b05..9d10c7929 100644
--- a/core/field_label_serializable.ts
+++ b/core/field_label_serializable.ts
@@ -16,12 +16,12 @@
  *    edited programmatically.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldLabelSerializable');
 
-import {FieldLabel} from './field_label.js';
-import * as fieldRegistry from './field_registry.js';
-import * as parsing from './utils/parsing.js';
+import {FieldLabel} from './field_label';
+import * as fieldRegistry from './field_registry';
+import * as parsing from './utils/parsing';
 
 
 /**
diff --git a/core/field_multilineinput.ts b/core/field_multilineinput.ts
index 505ad58ca..51f28c07a 100644
--- a/core/field_multilineinput.ts
+++ b/core/field_multilineinput.ts
@@ -12,22 +12,22 @@
  * Text Area field.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldMultilineInput');
 
-import * as Css from './css.js';
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import {FieldTextInput} from './field_textinput.js';
-import * as aria from './utils/aria.js';
-import * as dom from './utils/dom.js';
-import {KeyCodes} from './utils/keycodes.js';
-import * as parsing from './utils/parsing.js';
+import * as Css from './css';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import {FieldTextInput} from './field_textinput';
+import * as aria from './utils/aria';
+import * as dom from './utils/dom';
+import {KeyCodes} from './utils/keycodes';
+import * as parsing from './utils/parsing';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
-import {Svg} from './utils/svg.js';
-import * as userAgent from './utils/useragent.js';
-import * as WidgetDiv from './widgetdiv.js';
+import {Sentinel} from './utils/sentinel';
+import {Svg} from './utils/svg';
+import * as userAgent from './utils/useragent';
+import * as WidgetDiv from './widgetdiv';
 
 
 /**
diff --git a/core/field_number.ts b/core/field_number.ts
index c4f037441..6747c52da 100644
--- a/core/field_number.ts
+++ b/core/field_number.ts
@@ -12,15 +12,15 @@
  * Number input field
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldNumber');
 
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import {FieldTextInput} from './field_textinput.js';
-import * as aria from './utils/aria.js';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import {FieldTextInput} from './field_textinput';
+import * as aria from './utils/aria';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
+import {Sentinel} from './utils/sentinel';
 
 
 /**
diff --git a/core/field_registry.ts b/core/field_registry.ts
index 54e0a6d96..bbac7fbfd 100644
--- a/core/field_registry.ts
+++ b/core/field_registry.ts
@@ -16,14 +16,14 @@
  *    fields based on JSON.
  * @namespace Blockly.fieldRegistry
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.fieldRegistry');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from './field.js';
+import {Field} from './field';
 /* eslint-disable-next-line no-unused-vars */
-import {IRegistrableField} from './interfaces/i_registrable_field.js';
-import * as registry from './registry.js';
+import {IRegistrableField} from './interfaces/i_registrable_field';
+import * as registry from './registry';
 
 
 /**
diff --git a/core/field_textinput.ts b/core/field_textinput.ts
index 07571309f..f629076bd 100644
--- a/core/field_textinput.ts
+++ b/core/field_textinput.ts
@@ -12,32 +12,32 @@
  * Text input field.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldTextInput');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_change.js';
+import './events/events_block_change';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
-import * as dialog from './dialog.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import * as eventUtils from './events/utils.js';
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import {Msg} from './msg.js';
-import * as aria from './utils/aria.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {KeyCodes} from './utils/keycodes.js';
-import * as parsing from './utils/parsing.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
+import * as dialog from './dialog';
+import * as dropDownDiv from './dropdowndiv';
+import * as eventUtils from './events/utils';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import {Msg} from './msg';
+import * as aria from './utils/aria';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {KeyCodes} from './utils/keycodes';
+import * as parsing from './utils/parsing';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
-import * as userAgent from './utils/useragent.js';
-import * as WidgetDiv from './widgetdiv.js';
+import {Sentinel} from './utils/sentinel';
+import * as userAgent from './utils/useragent';
+import * as WidgetDiv from './widgetdiv';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/field_variable.ts b/core/field_variable.ts
index 358e4eeac..fb7728963 100644
--- a/core/field_variable.ts
+++ b/core/field_variable.ts
@@ -12,30 +12,30 @@
  * Variable input field.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FieldVariable');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_change.js';
+import './events/events_block_change';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
-import {Field} from './field.js';
-import {FieldDropdown} from './field_dropdown.js';
-import * as fieldRegistry from './field_registry.js';
-import * as internalConstants from './internal_constants.js';
+import {Block} from './block';
+import {Field} from './field';
+import {FieldDropdown} from './field_dropdown';
+import * as fieldRegistry from './field_registry';
+import * as internalConstants from './internal_constants';
 /* eslint-disable-next-line no-unused-vars */
-import {Menu} from './menu.js';
+import {Menu} from './menu';
 /* eslint-disable-next-line no-unused-vars */
-import {MenuItem} from './menuitem.js';
-import {Msg} from './msg.js';
-import * as parsing from './utils/parsing.js';
+import {MenuItem} from './menuitem';
+import {Msg} from './msg';
+import * as parsing from './utils/parsing';
 /* eslint-disable-next-line no-unused-vars */
-import {Sentinel} from './utils/sentinel.js';
-import {Size} from './utils/size.js';
-import {VariableModel} from './variable_model.js';
-import * as Variables from './variables.js';
-import * as Xml from './xml.js';
+import {Sentinel} from './utils/sentinel';
+import {Size} from './utils/size';
+import {VariableModel} from './variable_model';
+import * as Variables from './variables';
+import * as Xml from './xml';
 
 
 /**
diff --git a/core/flyout_base.ts b/core/flyout_base.ts
index 37a579ded..b6dc5586f 100644
--- a/core/flyout_base.ts
+++ b/core/flyout_base.ts
@@ -12,43 +12,43 @@
  * Flyout tray containing blocks which may be created.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Flyout');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
-import * as common from './common.js';
-import {ComponentManager} from './component_manager.js';
-import {DeleteArea} from './delete_area.js';
-import * as BlockCreate from './events/events_block_create.js';
-import * as VarCreate from './events/events_var_create.js';
-import * as eventUtils from './events/utils.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
+import * as common from './common';
+import {ComponentManager} from './component_manager';
+import {DeleteArea} from './delete_area';
+import * as BlockCreate from './events/events_block_create';
+import * as VarCreate from './events/events_var_create';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {FlyoutButton} from './flyout_button.js';
-import {FlyoutMetricsManager} from './flyout_metrics_manager.js';
-import * as Gesture from './gesture.js';
+import {FlyoutButton} from './flyout_button';
+import {FlyoutMetricsManager} from './flyout_metrics_manager';
+import * as Gesture from './gesture';
 /* eslint-disable-next-line no-unused-vars */
-import {IFlyout} from './interfaces/i_flyout.js';
+import {IFlyout} from './interfaces/i_flyout';
 /* eslint-disable-next-line no-unused-vars */
-import {Options} from './options.js';
-import * as blockRendering from './renderers/common/block_rendering.js';
-import {ScrollbarPair} from './scrollbar_pair.js';
-import * as blocks from './serialization/blocks.js';
-import * as Tooltip from './tooltip.js';
-import * as Touch from './touch.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import * as idGenerator from './utils/idgenerator.js';
+import {Options} from './options';
+import * as blockRendering from './renderers/common/block_rendering';
+import {ScrollbarPair} from './scrollbar_pair';
+import * as blocks from './serialization/blocks';
+import * as Tooltip from './tooltip';
+import * as Touch from './touch';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import * as idGenerator from './utils/idgenerator';
 /* eslint-disable-next-line no-unused-vars */
-import {Rect} from './utils/rect.js';
-import {Svg} from './utils/svg.js';
-import * as toolbox from './utils/toolbox.js';
-import * as Variables from './variables.js';
-import {WorkspaceSvg} from './workspace_svg.js';
-import * as Xml from './xml.js';
+import {Rect} from './utils/rect';
+import {Svg} from './utils/svg';
+import * as toolbox from './utils/toolbox';
+import * as Variables from './variables';
+import {WorkspaceSvg} from './workspace_svg';
+import * as Xml from './xml';
 
 
 enum FlyoutItemType {
diff --git a/core/flyout_button.ts b/core/flyout_button.ts
index bb29ffdc8..898fd83da 100644
--- a/core/flyout_button.ts
+++ b/core/flyout_button.ts
@@ -12,20 +12,20 @@
  * Class for a button in the flyout.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FlyoutButton');
 
-import * as browserEvents from './browser_events.js';
-import * as Css from './css.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import * as parsing from './utils/parsing.js';
-import * as style from './utils/style.js';
-import {Svg} from './utils/svg.js';
+import * as browserEvents from './browser_events';
+import * as Css from './css';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import * as parsing from './utils/parsing';
+import * as style from './utils/style';
+import {Svg} from './utils/svg';
 /* eslint-disable-next-line no-unused-vars */
-import * as toolbox from './utils/toolbox.js';
+import * as toolbox from './utils/toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/flyout_horizontal.ts b/core/flyout_horizontal.ts
index 7e433a913..bd8bd494b 100644
--- a/core/flyout_horizontal.ts
+++ b/core/flyout_horizontal.ts
@@ -12,23 +12,23 @@
  * Horizontal flyout tray containing blocks which may be created.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.HorizontalFlyout');
 
-import * as browserEvents from './browser_events.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import {Flyout, FlyoutItem} from './flyout_base.js';
+import * as browserEvents from './browser_events';
+import * as dropDownDiv from './dropdowndiv';
+import {Flyout, FlyoutItem} from './flyout_base';
 /* eslint-disable-next-line no-unused-vars */
-import {FlyoutButton} from './flyout_button.js';
+import {FlyoutButton} from './flyout_button';
 /* eslint-disable-next-line no-unused-vars */
-import {Options} from './options.js';
-import * as registry from './registry.js';
-import {Scrollbar} from './scrollbar.js';
+import {Options} from './options';
+import * as registry from './registry';
+import {Scrollbar} from './scrollbar';
 /* eslint-disable-next-line no-unused-vars */
-import {Coordinate} from './utils/coordinate.js';
-import {Rect} from './utils/rect.js';
-import * as toolbox from './utils/toolbox.js';
-import * as WidgetDiv from './widgetdiv.js';
+import {Coordinate} from './utils/coordinate';
+import {Rect} from './utils/rect';
+import * as toolbox from './utils/toolbox';
+import * as WidgetDiv from './widgetdiv';
 
 
 /**
diff --git a/core/flyout_metrics_manager.ts b/core/flyout_metrics_manager.ts
index 85fadbfcb..d1e64cda2 100644
--- a/core/flyout_metrics_manager.ts
+++ b/core/flyout_metrics_manager.ts
@@ -12,14 +12,14 @@
  * Calculates and reports flyout workspace metrics.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.FlyoutMetricsManager');
 
 /* eslint-disable-next-line no-unused-vars */
-import {IFlyout} from './interfaces/i_flyout.js';
-import {ContainerRegion, MetricsManager} from './metrics_manager.js';
+import {IFlyout} from './interfaces/i_flyout';
+import {ContainerRegion, MetricsManager} from './metrics_manager';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/flyout_vertical.ts b/core/flyout_vertical.ts
index 7e68b5963..80b7176f5 100644
--- a/core/flyout_vertical.ts
+++ b/core/flyout_vertical.ts
@@ -12,28 +12,28 @@
  * Layout code for a vertical variant of the flyout.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.VerticalFlyout');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './block.js';
+import './block';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './constants.js';
+import './constants';
 
-import * as browserEvents from './browser_events.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import {Flyout, FlyoutItem} from './flyout_base.js';
+import * as browserEvents from './browser_events';
+import * as dropDownDiv from './dropdowndiv';
+import {Flyout, FlyoutItem} from './flyout_base';
 /* eslint-disable-next-line no-unused-vars */
-import {FlyoutButton} from './flyout_button.js';
+import {FlyoutButton} from './flyout_button';
 /* eslint-disable-next-line no-unused-vars */
-import {Options} from './options.js';
-import * as registry from './registry.js';
-import {Scrollbar} from './scrollbar.js';
+import {Options} from './options';
+import * as registry from './registry';
+import {Scrollbar} from './scrollbar';
 /* eslint-disable-next-line no-unused-vars */
-import {Coordinate} from './utils/coordinate.js';
-import {Rect} from './utils/rect.js';
-import * as toolbox from './utils/toolbox.js';
-import * as WidgetDiv from './widgetdiv.js';
+import {Coordinate} from './utils/coordinate';
+import {Rect} from './utils/rect';
+import * as toolbox from './utils/toolbox';
+import * as WidgetDiv from './widgetdiv';
 
 
 /**
diff --git a/core/generator.ts b/core/generator.ts
index 0bcad0517..568b039da 100644
--- a/core/generator.ts
+++ b/core/generator.ts
@@ -14,17 +14,17 @@
  * Blockly code.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Generator');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
-import * as common from './common.js';
+import {Block} from './block';
+import * as common from './common';
 /* eslint-disable-next-line no-unused-vars */
-import {Names, NameType} from './names.js';
-import * as deprecation from './utils/deprecation.js';
+import {Names, NameType} from './names';
+import * as deprecation from './utils/deprecation';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 
 
 /**
diff --git a/core/gesture.ts b/core/gesture.ts
index 6d664581c..70c4c3835 100644
--- a/core/gesture.ts
+++ b/core/gesture.ts
@@ -14,41 +14,41 @@
  * or a tap.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Gesture');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './block_dragger.js';
+import './block_dragger';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_click.js';
+import './events/events_click';
 
-import * as blockAnimations from './block_animations.js';
+import * as blockAnimations from './block_animations';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
-import {BubbleDragger} from './bubble_dragger.js';
-import * as common from './common.js';
-import {config} from './config.js';
-import * as eventUtils from './events/utils.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
+import {BubbleDragger} from './bubble_dragger';
+import * as common from './common';
+import {config} from './config';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from './field.js';
+import {Field} from './field';
 /* eslint-disable-next-line no-unused-vars */
-import {IBlockDragger} from './interfaces/i_block_dragger.js';
+import {IBlockDragger} from './interfaces/i_block_dragger';
 /* eslint-disable-next-line no-unused-vars */
-import {IBubble} from './interfaces/i_bubble.js';
+import {IBubble} from './interfaces/i_bubble';
 /* eslint-disable-next-line no-unused-vars */
-import {IFlyout} from './interfaces/i_flyout.js';
-import * as internalConstants from './internal_constants.js';
-import * as registry from './registry.js';
-import * as Tooltip from './tooltip.js';
-import * as Touch from './touch.js';
-import {Coordinate} from './utils/coordinate.js';
-import {Workspace} from './workspace.js';
+import {IFlyout} from './interfaces/i_flyout';
+import * as internalConstants from './internal_constants';
+import * as registry from './registry';
+import * as Tooltip from './tooltip';
+import * as Touch from './touch';
+import {Coordinate} from './utils/coordinate';
+import {Workspace} from './workspace';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceCommentSvg} from './workspace_comment_svg.js';
-import {WorkspaceDragger} from './workspace_dragger.js';
+import {WorkspaceCommentSvg} from './workspace_comment_svg';
+import {WorkspaceDragger} from './workspace_dragger';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/grid.ts b/core/grid.ts
index 2ccd37473..c176dff57 100644
--- a/core/grid.ts
+++ b/core/grid.ts
@@ -14,12 +14,12 @@
  * Blockly.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Grid');
 
-import * as dom from './utils/dom.js';
-import {Svg} from './utils/svg.js';
-import * as userAgent from './utils/useragent.js';
+import * as dom from './utils/dom';
+import {Svg} from './utils/svg';
+import * as userAgent from './utils/useragent';
 
 
 /**
diff --git a/core/icon.ts b/core/icon.ts
index 464851de8..262c11485 100644
--- a/core/icon.ts
+++ b/core/icon.ts
@@ -12,19 +12,19 @@
  * Object representing an icon on a block.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Icon');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as browserEvents from './browser_events.js';
+import {BlockSvg} from './block_svg';
+import * as browserEvents from './browser_events';
 /* eslint-disable-next-line no-unused-vars */
-import {Bubble} from './bubble.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {Size} from './utils/size.js';
-import {Svg} from './utils/svg.js';
-import * as svgMath from './utils/svg_math.js';
+import {Bubble} from './bubble';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {Size} from './utils/size';
+import {Svg} from './utils/svg';
+import * as svgMath from './utils/svg_math';
 
 
 /**
diff --git a/core/inject.ts b/core/inject.ts
index 6095b1f10..b2111fadd 100644
--- a/core/inject.ts
+++ b/core/inject.ts
@@ -12,32 +12,32 @@
  * Functions for injecting Blockly into a web page.
  * @namespace Blockly.inject
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.inject');
 
-import {BlockDragSurfaceSvg} from './block_drag_surface.js';
+import {BlockDragSurfaceSvg} from './block_drag_surface';
 /* eslint-disable-next-line no-unused-vars */
-import {BlocklyOptions} from './blockly_options.js';
-import * as browserEvents from './browser_events.js';
-import * as bumpObjects from './bump_objects.js';
-import * as common from './common.js';
-import * as Css from './css.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import {Grid} from './grid.js';
-import {Msg} from './msg.js';
-import {Options} from './options.js';
-import {ScrollbarPair} from './scrollbar_pair.js';
-import {ShortcutRegistry} from './shortcut_registry.js';
-import * as Tooltip from './tooltip.js';
-import * as Touch from './touch.js';
-import * as aria from './utils/aria.js';
-import * as dom from './utils/dom.js';
-import {Svg} from './utils/svg.js';
-import * as userAgent from './utils/useragent.js';
-import * as WidgetDiv from './widgetdiv.js';
-import {Workspace} from './workspace.js';
-import {WorkspaceDragSurfaceSvg} from './workspace_drag_surface_svg.js';
-import {WorkspaceSvg} from './workspace_svg.js';
+import {BlocklyOptions} from './blockly_options';
+import * as browserEvents from './browser_events';
+import * as bumpObjects from './bump_objects';
+import * as common from './common';
+import * as Css from './css';
+import * as dropDownDiv from './dropdowndiv';
+import {Grid} from './grid';
+import {Msg} from './msg';
+import {Options} from './options';
+import {ScrollbarPair} from './scrollbar_pair';
+import {ShortcutRegistry} from './shortcut_registry';
+import * as Tooltip from './tooltip';
+import * as Touch from './touch';
+import * as aria from './utils/aria';
+import * as dom from './utils/dom';
+import {Svg} from './utils/svg';
+import * as userAgent from './utils/useragent';
+import * as WidgetDiv from './widgetdiv';
+import {Workspace} from './workspace';
+import {WorkspaceDragSurfaceSvg} from './workspace_drag_surface_svg';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/input.ts b/core/input.ts
index 9a297c7b0..a8ee2eaba 100644
--- a/core/input.ts
+++ b/core/input.ts
@@ -12,24 +12,24 @@
  * Object representing an input (value, statement, or dummy).
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Input');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './field_label.js';
+import './field_label';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
+import {BlockSvg} from './block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {Connection} from './connection.js';
+import {Connection} from './connection';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from './field.js';
-import * as fieldRegistry from './field_registry.js';
-import {inputTypes} from './input_types.js';
+import {Field} from './field';
+import * as fieldRegistry from './field_registry';
+import {inputTypes} from './input_types';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from './rendered_connection.js';
+import {RenderedConnection} from './rendered_connection';
 
 
 /**
diff --git a/core/input_types.ts b/core/input_types.ts
index c7ef64382..609b6c932 100644
--- a/core/input_types.ts
+++ b/core/input_types.ts
@@ -12,10 +12,10 @@
  * An enum for the possible types of inputs.
  * @namespace Blockly.inputTypes
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.inputTypes');
 
-import {ConnectionType} from './connection_type.js';
+import {ConnectionType} from './connection_type';
 
 
 /**
diff --git a/core/insertion_marker_manager.ts b/core/insertion_marker_manager.ts
index c509cd088..48df450a0 100644
--- a/core/insertion_marker_manager.ts
+++ b/core/insertion_marker_manager.ts
@@ -12,28 +12,28 @@
  * Class that controls updates to connections during drags.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.InsertionMarkerManager');
 
-import * as blockAnimations from './block_animations.js';
+import * as blockAnimations from './block_animations';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as common from './common.js';
-import {ComponentManager} from './component_manager.js';
-import {config} from './config.js';
-import {ConnectionType} from './connection_type.js';
-import * as constants from './constants.js';
-import * as eventUtils from './events/utils.js';
+import {BlockSvg} from './block_svg';
+import * as common from './common';
+import {ComponentManager} from './component_manager';
+import {config} from './config';
+import {ConnectionType} from './connection_type';
+import * as constants from './constants';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {IDeleteArea} from './interfaces/i_delete_area.js';
+import {IDeleteArea} from './interfaces/i_delete_area';
 /* eslint-disable-next-line no-unused-vars */
-import {IDragTarget} from './interfaces/i_drag_target.js';
+import {IDragTarget} from './interfaces/i_drag_target';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from './rendered_connection.js';
+import {RenderedConnection} from './rendered_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {Coordinate} from './utils/coordinate.js';
+import {Coordinate} from './utils/coordinate';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /** Represents a nearby valid connection. */
diff --git a/core/interfaces/i_ast_node_location.ts b/core/interfaces/i_ast_node_location.ts
index c9929382f..2842ef0bf 100644
--- a/core/interfaces/i_ast_node_location.ts
+++ b/core/interfaces/i_ast_node_location.ts
@@ -12,7 +12,7 @@
  * The interface for an AST node location.
  * @namespace Blockly.IASTNodeLocation
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IASTNodeLocation');
 
 
diff --git a/core/interfaces/i_ast_node_location_svg.ts b/core/interfaces/i_ast_node_location_svg.ts
index fe1f0926e..291e28884 100644
--- a/core/interfaces/i_ast_node_location_svg.ts
+++ b/core/interfaces/i_ast_node_location_svg.ts
@@ -12,11 +12,11 @@
  * The interface for an AST node location SVG.
  * @namespace Blockly.IASTNodeLocationSvg
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IASTNodeLocationSvg');
 
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocation} from './i_ast_node_location.js';
+import {IASTNodeLocation} from './i_ast_node_location';
 
 
 /**
diff --git a/core/interfaces/i_ast_node_location_with_block.ts b/core/interfaces/i_ast_node_location_with_block.ts
index 203079772..a8966180a 100644
--- a/core/interfaces/i_ast_node_location_with_block.ts
+++ b/core/interfaces/i_ast_node_location_with_block.ts
@@ -14,15 +14,15 @@
  * block.
  * @namespace Blockly.IASTNodeLocationWithBlock
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IASTNodeLocationWithBlock');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../block.js';
+import '../block';
 
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocation} from './i_ast_node_location.js';
+import {IASTNodeLocation} from './i_ast_node_location';
 
 
 /**
diff --git a/core/interfaces/i_autohideable.ts b/core/interfaces/i_autohideable.ts
index 2ba5cf201..7a25be7bb 100644
--- a/core/interfaces/i_autohideable.ts
+++ b/core/interfaces/i_autohideable.ts
@@ -14,11 +14,11 @@
  * when WorkspaceSvg.hideChaff is called.
  * @namespace Blockly.IAutoHideable
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IAutoHideable');
 
 /* eslint-disable-next-line no-unused-vars */
-import {IComponent} from './i_component.js';
+import {IComponent} from './i_component';
 
 
 /**
diff --git a/core/interfaces/i_block_dragger.ts b/core/interfaces/i_block_dragger.ts
index cf418838d..0cb712aed 100644
--- a/core/interfaces/i_block_dragger.ts
+++ b/core/interfaces/i_block_dragger.ts
@@ -12,15 +12,15 @@
  * The interface for a block dragger.
  * @namespace Blockly.IBlockDragger
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IBlockDragger');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../block_svg.js';
+import '../block_svg';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/coordinate.js';
+import '../utils/coordinate';
 
 
 /**
diff --git a/core/interfaces/i_bounded_element.ts b/core/interfaces/i_bounded_element.ts
index 10d27c3ba..5d9e2a54f 100644
--- a/core/interfaces/i_bounded_element.ts
+++ b/core/interfaces/i_bounded_element.ts
@@ -12,12 +12,12 @@
  * The interface for a bounded element.
  * @namespace Blockly.IBoundedElement
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IBoundedElement');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/rect.js';
+import '../utils/rect';
 
 
 /**
diff --git a/core/interfaces/i_bubble.ts b/core/interfaces/i_bubble.ts
index 1da315b6b..6470e61bd 100644
--- a/core/interfaces/i_bubble.ts
+++ b/core/interfaces/i_bubble.ts
@@ -12,20 +12,20 @@
  * The interface for a bubble.
  * @namespace Blockly.IBubble
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IBubble');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../block_drag_surface.js';
+import '../block_drag_surface';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/coordinate.js';
+import '../utils/coordinate';
 
 /* eslint-disable-next-line no-unused-vars */
-import {IContextMenu} from './i_contextmenu.js';
+import {IContextMenu} from './i_contextmenu';
 /* eslint-disable-next-line no-unused-vars */
-import {IDraggable} from './i_draggable.js';
+import {IDraggable} from './i_draggable';
 
 
 /**
diff --git a/core/interfaces/i_collapsible_toolbox_item.ts b/core/interfaces/i_collapsible_toolbox_item.ts
index 534bdf818..f05bdf1ea 100644
--- a/core/interfaces/i_collapsible_toolbox_item.ts
+++ b/core/interfaces/i_collapsible_toolbox_item.ts
@@ -12,15 +12,15 @@
  * The interface for a collapsible toolbox item.
  * @namespace Blockly.ICollapsibleToolboxItem
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.ICollapsibleToolboxItem');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './i_toolbox_item.js';
+import './i_toolbox_item';
 
-import {ISelectableToolboxItem} from './i_selectable_toolbox_item.js';
+import {ISelectableToolboxItem} from './i_selectable_toolbox_item';
 
 
 /**
diff --git a/core/interfaces/i_component.ts b/core/interfaces/i_component.ts
index 9f8a19660..df80fed08 100644
--- a/core/interfaces/i_component.ts
+++ b/core/interfaces/i_component.ts
@@ -14,7 +14,7 @@
  * the ComponentManager.
  * @namespace Blockly.IComponent
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IComponent');
 
 
diff --git a/core/interfaces/i_connection_checker.ts b/core/interfaces/i_connection_checker.ts
index 77585922b..19ad9f3d9 100644
--- a/core/interfaces/i_connection_checker.ts
+++ b/core/interfaces/i_connection_checker.ts
@@ -14,15 +14,15 @@
  * checking whether a potential connection is safe and valid.
  * @namespace Blockly.IConnectionChecker
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IConnectionChecker');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../connection.js';
+import '../connection';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../rendered_connection.js';
+import '../rendered_connection';
 
 
 /**
diff --git a/core/interfaces/i_contextmenu.ts b/core/interfaces/i_contextmenu.ts
index 983e9a78b..0d04a2545 100644
--- a/core/interfaces/i_contextmenu.ts
+++ b/core/interfaces/i_contextmenu.ts
@@ -12,7 +12,7 @@
  * The interface for an object that supports a right-click.
  * @namespace Blockly.IContextMenu
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IContextMenu');
 
 
diff --git a/core/interfaces/i_copyable.ts b/core/interfaces/i_copyable.ts
index 20fec55c0..5c1a776db 100644
--- a/core/interfaces/i_copyable.ts
+++ b/core/interfaces/i_copyable.ts
@@ -12,14 +12,14 @@
  * The interface for an object that is copyable.
  * @namespace Blockly.ICopyable
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.ICopyable');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../workspace_svg.js';
+import {WorkspaceSvg} from '../workspace_svg';
 
-import {ISelectable} from './i_selectable.js';
+import {ISelectable} from './i_selectable';
 
 
 /** @alias Blockly.ICopyable */
diff --git a/core/interfaces/i_deletable.ts b/core/interfaces/i_deletable.ts
index 599313d45..5e061ee35 100644
--- a/core/interfaces/i_deletable.ts
+++ b/core/interfaces/i_deletable.ts
@@ -12,7 +12,7 @@
  * The interface for an object that is deletable.
  * @namespace Blockly.IDeletable
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IDeletable');
 
 
diff --git a/core/interfaces/i_delete_area.ts b/core/interfaces/i_delete_area.ts
index 5f68ab92c..b60239596 100644
--- a/core/interfaces/i_delete_area.ts
+++ b/core/interfaces/i_delete_area.ts
@@ -14,15 +14,15 @@
  * that is dropped on top of it.
  * @namespace Blockly.IDeleteArea
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IDeleteArea');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './i_draggable.js';
+import './i_draggable';
 
-import {IDragTarget} from './i_drag_target.js';
+import {IDragTarget} from './i_drag_target';
 
 
 /**
diff --git a/core/interfaces/i_drag_target.ts b/core/interfaces/i_drag_target.ts
index 7da9209f7..ebf1fe4ac 100644
--- a/core/interfaces/i_drag_target.ts
+++ b/core/interfaces/i_drag_target.ts
@@ -14,18 +14,18 @@
  * block is dropped on top of it.
  * @namespace Blockly.IDragTarget
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IDragTarget');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './i_draggable.js';
+import './i_draggable';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/rect.js';
+import '../utils/rect';
 
-import {IComponent} from './i_component.js';
+import {IComponent} from './i_component';
 
 
 /**
diff --git a/core/interfaces/i_draggable.ts b/core/interfaces/i_draggable.ts
index 24f12a840..e09d8c3a5 100644
--- a/core/interfaces/i_draggable.ts
+++ b/core/interfaces/i_draggable.ts
@@ -12,11 +12,11 @@
  * The interface for an object that is draggable.
  * @namespace Blockly.IDraggable
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IDraggable');
 
 /* eslint-disable-next-line no-unused-vars */
-import {IDeletable} from './i_deletable.js';
+import {IDeletable} from './i_deletable';
 
 
 /**
diff --git a/core/interfaces/i_flyout.ts b/core/interfaces/i_flyout.ts
index 471f6d967..f9838b999 100644
--- a/core/interfaces/i_flyout.ts
+++ b/core/interfaces/i_flyout.ts
@@ -12,27 +12,27 @@
  * The interface for a flyout.
  * @namespace Blockly.IFlyout
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IFlyout');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/toolbox.js';
+import '../utils/toolbox';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../block_svg.js';
+import '../block_svg';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/coordinate.js';
+import '../utils/coordinate';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/svg.js';
+import '../utils/svg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../workspace_svg.js';
+import {WorkspaceSvg} from '../workspace_svg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {IRegistrable} from './i_registrable.js';
+import {IRegistrable} from './i_registrable';
 
 
 /**
diff --git a/core/interfaces/i_keyboard_accessible.ts b/core/interfaces/i_keyboard_accessible.ts
index f31ef205d..b8c238ed6 100644
--- a/core/interfaces/i_keyboard_accessible.ts
+++ b/core/interfaces/i_keyboard_accessible.ts
@@ -12,12 +12,12 @@
  * The interface for objects that handle keyboard shortcuts.
  * @namespace Blockly.IKeyboardAccessible
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IKeyboardAccessible');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../shortcut_registry.js';
+import '../shortcut_registry';
 
 
 /**
diff --git a/core/interfaces/i_metrics_manager.ts b/core/interfaces/i_metrics_manager.ts
index 3c1bc85dc..107e8179b 100644
--- a/core/interfaces/i_metrics_manager.ts
+++ b/core/interfaces/i_metrics_manager.ts
@@ -12,18 +12,18 @@
  * The interface for a metrics manager.
  * @namespace Blockly.IMetricsManager
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IMetricsManager');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../metrics_manager.js';
+import '../metrics_manager';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/metrics.js';
+import '../utils/metrics';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/size.js';
+import '../utils/size';
 
 
 /**
diff --git a/core/interfaces/i_movable.ts b/core/interfaces/i_movable.ts
index 6bc904941..baecf783e 100644
--- a/core/interfaces/i_movable.ts
+++ b/core/interfaces/i_movable.ts
@@ -12,7 +12,7 @@
  * The interface for an object that is movable.
  * @namespace Blockly.IMovable
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IMovable');
 
 
diff --git a/core/interfaces/i_positionable.ts b/core/interfaces/i_positionable.ts
index c8fcdeab1..a304fce90 100644
--- a/core/interfaces/i_positionable.ts
+++ b/core/interfaces/i_positionable.ts
@@ -12,18 +12,18 @@
  * The interface for a positionable UI element.
  * @namespace Blockly.IPositionable
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IPositionable');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../metrics_manager.js';
+import '../metrics_manager';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/rect.js';
+import '../utils/rect';
 
-import {IComponent} from './i_component.js';
+import {IComponent} from './i_component';
 
 
 /**
diff --git a/core/interfaces/i_registrable.ts b/core/interfaces/i_registrable.ts
index c25749244..a12fd2b5a 100644
--- a/core/interfaces/i_registrable.ts
+++ b/core/interfaces/i_registrable.ts
@@ -14,7 +14,7 @@
  *    (Ex. Toolbox, Fields, Renderers)
  * @namespace Blockly.IRegistrable
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IRegistrable');
 
 
diff --git a/core/interfaces/i_registrable_field.ts b/core/interfaces/i_registrable_field.ts
index f6929b9f8..4b35ed3c0 100644
--- a/core/interfaces/i_registrable_field.ts
+++ b/core/interfaces/i_registrable_field.ts
@@ -12,11 +12,11 @@
  * The interface for a Blockly field that can be registered.
  * @namespace Blockly.IRegistrableField
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IRegistrableField');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from '../field.js';
+import {Field} from '../field';
 
 
 type fromJson = (p1: object) => Field;
diff --git a/core/interfaces/i_selectable.ts b/core/interfaces/i_selectable.ts
index 497f0c1c5..3f15f51e9 100644
--- a/core/interfaces/i_selectable.ts
+++ b/core/interfaces/i_selectable.ts
@@ -12,13 +12,13 @@
  * The interface for an object that is selectable.
  * @namespace Blockly.ISelectable
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.ISelectable');
 
 // eslint-disable-next-line no-unused-vars
-import {IDeletable} from './i_deletable.js';
+import {IDeletable} from './i_deletable';
 // eslint-disable-next-line no-unused-vars
-import {IMovable} from './i_movable.js';
+import {IMovable} from './i_movable';
 
 
 /**
diff --git a/core/interfaces/i_selectable_toolbox_item.ts b/core/interfaces/i_selectable_toolbox_item.ts
index 411959b04..f9990b765 100644
--- a/core/interfaces/i_selectable_toolbox_item.ts
+++ b/core/interfaces/i_selectable_toolbox_item.ts
@@ -12,15 +12,15 @@
  * The interface for a selectable toolbox item.
  * @namespace Blockly.ISelectableToolboxItem
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.ISelectableToolboxItem');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/toolbox.js';
+import '../utils/toolbox';
 
 /* eslint-disable-next-line no-unused-vars */
-import {IToolboxItem} from './i_toolbox_item.js';
+import {IToolboxItem} from './i_toolbox_item';
 
 
 /**
diff --git a/core/interfaces/i_serializer.ts b/core/interfaces/i_serializer.ts
index 3f1d8ebfd..7ea3f734a 100644
--- a/core/interfaces/i_serializer.ts
+++ b/core/interfaces/i_serializer.ts
@@ -14,11 +14,11 @@
  *     serializing part of the workspace.
  * @namespace Blockly.serialization.ISerializer
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.serialization.ISerializer');
 
 // eslint-disable-next-line no-unused-vars
-import {Workspace} from '../workspace.js';
+import {Workspace} from '../workspace';
 
 
 /**
diff --git a/core/interfaces/i_styleable.ts b/core/interfaces/i_styleable.ts
index 292e18d56..7e03a28f9 100644
--- a/core/interfaces/i_styleable.ts
+++ b/core/interfaces/i_styleable.ts
@@ -12,7 +12,7 @@
  * The interface for an object that a style can be added to.
  * @namespace Blockly.IStyleable
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IStyleable');
 
 
diff --git a/core/interfaces/i_toolbox.ts b/core/interfaces/i_toolbox.ts
index 98dd493d0..03460c38a 100644
--- a/core/interfaces/i_toolbox.ts
+++ b/core/interfaces/i_toolbox.ts
@@ -12,24 +12,24 @@
  * The interface for a toolbox.
  * @namespace Blockly.IToolbox
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IToolbox');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../utils/toolbox.js';
+import '../utils/toolbox';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './i_flyout.js';
+import './i_flyout';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './i_toolbox_item.js';
+import './i_toolbox_item';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../workspace_svg.js';
+import '../workspace_svg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {IRegistrable} from './i_registrable.js';
+import {IRegistrable} from './i_registrable';
 
 
 /**
diff --git a/core/interfaces/i_toolbox_item.ts b/core/interfaces/i_toolbox_item.ts
index 7827444ab..f1d40ef08 100644
--- a/core/interfaces/i_toolbox_item.ts
+++ b/core/interfaces/i_toolbox_item.ts
@@ -12,7 +12,7 @@
  * The interface for a toolbox item.
  * @namespace Blockly.IToolboxItem
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.IToolboxItem');
 
 
diff --git a/core/internal_constants.ts b/core/internal_constants.ts
index 3a53ee55e..91d7e782e 100644
--- a/core/internal_constants.ts
+++ b/core/internal_constants.ts
@@ -14,10 +14,10 @@
  * use these constants outside of the core library.
  * @namespace Blockly.internalConstants
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.internalConstants');
 
-import {ConnectionType} from './connection_type.js';
+import {ConnectionType} from './connection_type';
 
 
 /**
diff --git a/core/keyboard_nav/ast_node.ts b/core/keyboard_nav/ast_node.ts
index 626290c4f..d79981ff4 100644
--- a/core/keyboard_nav/ast_node.ts
+++ b/core/keyboard_nav/ast_node.ts
@@ -14,25 +14,25 @@
  * Used to traverse the Blockly AST.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.ASTNode');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
+import {Block} from '../block';
 /* eslint-disable-next-line no-unused-vars */
-import {Connection} from '../connection.js';
-import {ConnectionType} from '../connection_type.js';
+import {Connection} from '../connection';
+import {ConnectionType} from '../connection_type';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from '../field.js';
+import {Field} from '../field';
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from '../input.js';
+import {Input} from '../input';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocation} from '../interfaces/i_ast_node_location.js';
+import {IASTNodeLocation} from '../interfaces/i_ast_node_location';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocationWithBlock} from '../interfaces/i_ast_node_location_with_block.js';
-import {Coordinate} from '../utils/coordinate.js';
+import {IASTNodeLocationWithBlock} from '../interfaces/i_ast_node_location_with_block';
+import {Coordinate} from '../utils/coordinate';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from '../workspace.js';
+import {Workspace} from '../workspace';
 
 
 /**
diff --git a/core/keyboard_nav/basic_cursor.ts b/core/keyboard_nav/basic_cursor.ts
index 53416da04..b46e5ebfd 100644
--- a/core/keyboard_nav/basic_cursor.ts
+++ b/core/keyboard_nav/basic_cursor.ts
@@ -14,13 +14,13 @@
  * Used to demo switching between different cursors.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.BasicCursor');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 
-import {ASTNode} from './ast_node.js';
-import {Cursor} from './cursor.js';
+import {ASTNode} from './ast_node';
+import {Cursor} from './cursor';
 
 
 /**
diff --git a/core/keyboard_nav/cursor.ts b/core/keyboard_nav/cursor.ts
index 2db5007a5..3119f9fc0 100644
--- a/core/keyboard_nav/cursor.ts
+++ b/core/keyboard_nav/cursor.ts
@@ -14,13 +14,13 @@
  * Used primarily for keyboard navigation.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Cursor');
 
-import * as registry from '../registry.js';
+import * as registry from '../registry';
 
-import {ASTNode} from './ast_node.js';
-import {Marker} from './marker.js';
+import {ASTNode} from './ast_node';
+import {Marker} from './marker';
 
 
 /**
diff --git a/core/keyboard_nav/marker.ts b/core/keyboard_nav/marker.ts
index 292e3816f..20f7e24c1 100644
--- a/core/keyboard_nav/marker.ts
+++ b/core/keyboard_nav/marker.ts
@@ -14,14 +14,14 @@
  * Used primarily for keyboard navigation to show a marked location.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Marker');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {MarkerSvg} from '../renderers/common/marker_svg.js';
+import {MarkerSvg} from '../renderers/common/marker_svg';
 
-import {ASTNode} from './ast_node.js';
+import {ASTNode} from './ast_node';
 
 
 /**
diff --git a/core/keyboard_nav/tab_navigate_cursor.ts b/core/keyboard_nav/tab_navigate_cursor.ts
index 6f6810e9d..fd8e74db6 100644
--- a/core/keyboard_nav/tab_navigate_cursor.ts
+++ b/core/keyboard_nav/tab_navigate_cursor.ts
@@ -14,14 +14,14 @@
  * between tab navigable fields.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.TabNavigateCursor');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from '../field.js';
+import {Field} from '../field';
 
-import {ASTNode} from './ast_node.js';
-import {BasicCursor} from './basic_cursor.js';
+import {ASTNode} from './ast_node';
+import {BasicCursor} from './basic_cursor';
 
 
 /**
diff --git a/core/marker_manager.ts b/core/marker_manager.ts
index f092fb424..61776d124 100644
--- a/core/marker_manager.ts
+++ b/core/marker_manager.ts
@@ -12,15 +12,15 @@
  * Object in charge of managing markers and the cursor.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.MarkerManager');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Cursor} from './keyboard_nav/cursor.js';
+import {Cursor} from './keyboard_nav/cursor';
 /* eslint-disable-next-line no-unused-vars */
-import {Marker} from './keyboard_nav/marker.js';
+import {Marker} from './keyboard_nav/marker';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/menu.ts b/core/menu.ts
index 7dc72a895..c2f830347 100644
--- a/core/menu.ts
+++ b/core/menu.ts
@@ -12,19 +12,19 @@
  * Blockly menu similar to Closure's goog.ui.Menu
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Menu');
 
-import * as browserEvents from './browser_events.js';
+import * as browserEvents from './browser_events';
 /* eslint-disable-next-line no-unused-vars */
-import {MenuItem} from './menuitem.js';
-import * as aria from './utils/aria.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {KeyCodes} from './utils/keycodes.js';
+import {MenuItem} from './menuitem';
+import * as aria from './utils/aria';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {KeyCodes} from './utils/keycodes';
 /* eslint-disable-next-line no-unused-vars */
-import {Size} from './utils/size.js';
-import * as style from './utils/style.js';
+import {Size} from './utils/size';
+import * as style from './utils/style';
 
 
 /**
diff --git a/core/menuitem.ts b/core/menuitem.ts
index c85e649a7..b495d1cee 100644
--- a/core/menuitem.ts
+++ b/core/menuitem.ts
@@ -12,12 +12,12 @@
  * Blockly menu item similar to Closure's goog.ui.MenuItem
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.MenuItem');
 
-import * as aria from './utils/aria.js';
-import * as dom from './utils/dom.js';
-import * as idGenerator from './utils/idgenerator.js';
+import * as aria from './utils/aria';
+import * as dom from './utils/dom';
+import * as idGenerator from './utils/idgenerator';
 
 
 /**
diff --git a/core/metrics_manager.ts b/core/metrics_manager.ts
index 4007a783c..8ee2692ce 100644
--- a/core/metrics_manager.ts
+++ b/core/metrics_manager.ts
@@ -12,22 +12,22 @@
  * Calculates and reports workspace metrics.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.MetricsManager');
 
 /* eslint-disable-next-line no-unused-vars */
-import {IFlyout} from './interfaces/i_flyout.js';
+import {IFlyout} from './interfaces/i_flyout';
 /* eslint-disable-next-line no-unused-vars */
-import {IMetricsManager} from './interfaces/i_metrics_manager.js';
+import {IMetricsManager} from './interfaces/i_metrics_manager';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolbox} from './interfaces/i_toolbox.js';
-import * as registry from './registry.js';
+import {IToolbox} from './interfaces/i_toolbox';
+import * as registry from './registry';
 /* eslint-disable-next-line no-unused-vars */
-import {Metrics} from './utils/metrics.js';
-import {Size} from './utils/size.js';
-import * as toolboxUtils from './utils/toolbox.js';
+import {Metrics} from './utils/metrics';
+import {Size} from './utils/size';
+import * as toolboxUtils from './utils/toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/msg.ts b/core/msg.ts
index d4c9be7b4..d928248bb 100644
--- a/core/msg.ts
+++ b/core/msg.ts
@@ -12,7 +12,7 @@
  * Empty name space for the Message singleton.
  * @namespace Blockly.Msg
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Msg');
 
 
diff --git a/core/mutator.ts b/core/mutator.ts
index dd147f465..5cb63c925 100644
--- a/core/mutator.ts
+++ b/core/mutator.ts
@@ -14,35 +14,35 @@
  * user to change the shape of a block using a nested blocks editor.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Mutator');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_bubble_open.js';
+import './events/events_bubble_open';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
+import {BlockSvg} from './block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {BlocklyOptions} from './blockly_options.js';
-import {Bubble} from './bubble.js';
-import {config} from './config.js';
+import {BlocklyOptions} from './blockly_options';
+import {Bubble} from './bubble';
+import {config} from './config';
 /* eslint-disable-next-line no-unused-vars */
-import {Connection} from './connection.js';
+import {Connection} from './connection';
 /* eslint-disable-next-line no-unused-vars */
-import {Abstract} from './events/events_abstract.js';
-import {BlockChange} from './events/events_block_change.js';
-import * as eventUtils from './events/utils.js';
-import {Icon} from './icon.js';
-import {Options} from './options.js';
+import {Abstract} from './events/events_abstract';
+import {BlockChange} from './events/events_block_change';
+import * as eventUtils from './events/utils';
+import {Icon} from './icon';
+import {Options} from './options';
 /* eslint-disable-next-line no-unused-vars */
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {Svg} from './utils/svg.js';
-import * as toolbox from './utils/toolbox.js';
-import * as xml from './utils/xml.js';
-import {WorkspaceSvg} from './workspace_svg.js';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {Svg} from './utils/svg';
+import * as toolbox from './utils/toolbox';
+import * as xml from './utils/xml';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/names.ts b/core/names.ts
index 046a7ee00..17737456e 100644
--- a/core/names.ts
+++ b/core/names.ts
@@ -12,19 +12,19 @@
  * Utility functions for handling variable and procedure names.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Names');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './procedures.js';
+import './procedures';
 
-import {Msg} from './msg.js';
-import * as Procedures from './procedures.js';
+import {Msg} from './msg';
+import * as Procedures from './procedures';
 /* eslint-disable-next-line no-unused-vars */
-import {VariableMap} from './variable_map.js';
-import * as Variables from './variables.js';
+import {VariableMap} from './variable_map';
+import * as Variables from './variables';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 
 
 /**
diff --git a/core/options.ts b/core/options.ts
index 99935c3ed..08c2e25bd 100644
--- a/core/options.ts
+++ b/core/options.ts
@@ -12,20 +12,20 @@
  * Object that controls settings for the workspace.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Options');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlocklyOptions} from './blockly_options.js';
-import * as registry from './registry.js';
-import {Theme} from './theme.js';
-import {Classic} from './theme/classic.js';
-import * as idGenerator from './utils/idgenerator.js';
+import {BlocklyOptions} from './blockly_options';
+import * as registry from './registry';
+import {Theme} from './theme';
+import {Classic} from './theme/classic';
+import * as idGenerator from './utils/idgenerator';
 /* eslint-disable-next-line no-unused-vars */
-import {Metrics} from './utils/metrics.js';
-import * as toolbox from './utils/toolbox.js';
+import {Metrics} from './utils/metrics';
+import * as toolbox from './utils/toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/positionable_helpers.ts b/core/positionable_helpers.ts
index 3965996b0..c540cd4e7 100644
--- a/core/positionable_helpers.ts
+++ b/core/positionable_helpers.ts
@@ -12,21 +12,21 @@
  * Utility functions for positioning UI elements.
  * @namespace Blockly.uiPosition
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.uiPosition');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './metrics_manager.js';
+import './metrics_manager';
 
-import {UiMetrics} from './metrics_manager.js';
-import {Scrollbar} from './scrollbar.js';
-import {Rect} from './utils/rect.js';
+import {UiMetrics} from './metrics_manager';
+import {Scrollbar} from './scrollbar';
+import {Rect} from './utils/rect';
 /* eslint-disable-next-line no-unused-vars */
-import {Size} from './utils/size.js';
-import * as toolbox from './utils/toolbox.js';
+import {Size} from './utils/size';
+import * as toolbox from './utils/toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/procedures.ts b/core/procedures.ts
index f0d87a3a2..537e0ea03 100644
--- a/core/procedures.ts
+++ b/core/procedures.ts
@@ -12,32 +12,32 @@
  * Utility functions for handling procedures.
  * @namespace Blockly.Procedures
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Procedures');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_change.js';
+import './events/events_block_change';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import {Blocks} from './blocks.js';
+import {BlockSvg} from './block_svg';
+import {Blocks} from './blocks';
 /* eslint-disable-next-line no-unused-vars */
-import {Abstract} from './events/events_abstract.js';
+import {Abstract} from './events/events_abstract';
 /* eslint-disable-next-line no-unused-vars */
-import {BubbleOpen} from './events/events_bubble_open.js';
-import * as eventUtils from './events/utils.js';
+import {BubbleOpen} from './events/events_bubble_open';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from './field.js';
-import {Msg} from './msg.js';
-import {Names} from './names.js';
-import * as utilsXml from './utils/xml.js';
-import * as Variables from './variables.js';
-import {Workspace} from './workspace.js';
+import {Field} from './field';
+import {Msg} from './msg';
+import {Names} from './names';
+import * as utilsXml from './utils/xml';
+import * as Variables from './variables';
+import {Workspace} from './workspace';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
-import * as Xml from './xml.js';
+import {WorkspaceSvg} from './workspace_svg';
+import * as Xml from './xml';
 
 
 /**
diff --git a/core/registry.ts b/core/registry.ts
index c4d5c4594..4aa61e3a6 100644
--- a/core/registry.ts
+++ b/core/registry.ts
@@ -14,35 +14,35 @@
  *    for registering and unregistering different types of classes.
  * @namespace Blockly.registry
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.registry');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Abstract} from './events/events_abstract.js';
+import {Abstract} from './events/events_abstract';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from './field.js';
+import {Field} from './field';
 /* eslint-disable-next-line no-unused-vars */
-import {IBlockDragger} from './interfaces/i_block_dragger.js';
+import {IBlockDragger} from './interfaces/i_block_dragger';
 /* eslint-disable-next-line no-unused-vars */
-import {IConnectionChecker} from './interfaces/i_connection_checker.js';
+import {IConnectionChecker} from './interfaces/i_connection_checker';
 /* eslint-disable-next-line no-unused-vars */
-import {IFlyout} from './interfaces/i_flyout.js';
+import {IFlyout} from './interfaces/i_flyout';
 /* eslint-disable-next-line no-unused-vars */
-import {IMetricsManager} from './interfaces/i_metrics_manager.js';
+import {IMetricsManager} from './interfaces/i_metrics_manager';
 /* eslint-disable-next-line no-unused-vars */
-import {ISerializer} from './interfaces/i_serializer.js';
+import {ISerializer} from './interfaces/i_serializer';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolbox} from './interfaces/i_toolbox.js';
+import {IToolbox} from './interfaces/i_toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {Cursor} from './keyboard_nav/cursor.js';
+import {Cursor} from './keyboard_nav/cursor';
 /* eslint-disable-next-line no-unused-vars */
-import {Options} from './options.js';
+import {Options} from './options';
 /* eslint-disable-next-line no-unused-vars */
-import {Renderer} from './renderers/common/renderer.js';
+import {Renderer} from './renderers/common/renderer';
 /* eslint-disable-next-line no-unused-vars */
-import {Theme} from './theme.js';
+import {Theme} from './theme';
 /* eslint-disable-next-line no-unused-vars */
-import {ToolboxItem} from './toolbox/toolbox_item.js';
+import {ToolboxItem} from './toolbox/toolbox_item';
 
 
 /**
diff --git a/core/rendered_connection.ts b/core/rendered_connection.ts
index 25155ec73..429067f8f 100644
--- a/core/rendered_connection.ts
+++ b/core/rendered_connection.ts
@@ -12,26 +12,26 @@
  * Components for creating connections between blocks.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.RenderedConnection');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import * as common from './common.js';
-import {config} from './config.js';
-import {Connection} from './connection.js';
+import {BlockSvg} from './block_svg';
+import * as common from './common';
+import {config} from './config';
+import {Connection} from './connection';
 /* eslint-disable-next-line no-unused-vars */
-import {ConnectionDB} from './connection_db.js';
-import {ConnectionType} from './connection_type.js';
-import * as eventUtils from './events/utils.js';
-import * as internalConstants from './internal_constants.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {Svg} from './utils/svg.js';
-import * as svgMath from './utils/svg_math.js';
-import * as svgPaths from './utils/svg_paths.js';
+import {ConnectionDB} from './connection_db';
+import {ConnectionType} from './connection_type';
+import * as eventUtils from './events/utils';
+import * as internalConstants from './internal_constants';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {Svg} from './utils/svg';
+import * as svgMath from './utils/svg_math';
+import * as svgPaths from './utils/svg_paths';
 
 
 /** A shape that has a pathDown property. */
diff --git a/core/renderers/common/block_rendering.ts b/core/renderers/common/block_rendering.ts
index 21f5c64b1..c914976f4 100644
--- a/core/renderers/common/block_rendering.ts
+++ b/core/renderers/common/block_rendering.ts
@@ -12,45 +12,45 @@
  * Namespace for block rendering functionality.
  * @namespace Blockly.blockRendering
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering');
 
-import * as registry from '../../registry.js';
+import * as registry from '../../registry';
 /* eslint-disable-next-line no-unused-vars */
-import {Theme} from '../../theme.js';
-import * as deprecation from '../../utils/deprecation.js';
-import {Measurable} from '../measurables/base.js';
-import {BottomRow} from '../measurables/bottom_row.js';
-import {Connection} from '../measurables/connection.js';
-import {ExternalValueInput} from '../measurables/external_value_input.js';
-import {Field} from '../measurables/field.js';
-import {Hat} from '../measurables/hat.js';
-import {Icon} from '../measurables/icon.js';
-import {InRowSpacer} from '../measurables/in_row_spacer.js';
-import {InlineInput} from '../measurables/inline_input.js';
-import {InputConnection} from '../measurables/input_connection.js';
-import {InputRow} from '../measurables/input_row.js';
-import {JaggedEdge} from '../measurables/jagged_edge.js';
-import {NextConnection} from '../measurables/next_connection.js';
-import {OutputConnection} from '../measurables/output_connection.js';
-import {PreviousConnection} from '../measurables/previous_connection.js';
-import {RoundCorner} from '../measurables/round_corner.js';
-import {Row} from '../measurables/row.js';
-import {SpacerRow} from '../measurables/spacer_row.js';
-import {SquareCorner} from '../measurables/square_corner.js';
-import {StatementInput} from '../measurables/statement_input.js';
-import {TopRow} from '../measurables/top_row.js';
-import {Types} from '../measurables/types.js';
+import {Theme} from '../../theme';
+import * as deprecation from '../../utils/deprecation';
+import {Measurable} from '../measurables/base';
+import {BottomRow} from '../measurables/bottom_row';
+import {Connection} from '../measurables/connection';
+import {ExternalValueInput} from '../measurables/external_value_input';
+import {Field} from '../measurables/field';
+import {Hat} from '../measurables/hat';
+import {Icon} from '../measurables/icon';
+import {InRowSpacer} from '../measurables/in_row_spacer';
+import {InlineInput} from '../measurables/inline_input';
+import {InputConnection} from '../measurables/input_connection';
+import {InputRow} from '../measurables/input_row';
+import {JaggedEdge} from '../measurables/jagged_edge';
+import {NextConnection} from '../measurables/next_connection';
+import {OutputConnection} from '../measurables/output_connection';
+import {PreviousConnection} from '../measurables/previous_connection';
+import {RoundCorner} from '../measurables/round_corner';
+import {Row} from '../measurables/row';
+import {SpacerRow} from '../measurables/spacer_row';
+import {SquareCorner} from '../measurables/square_corner';
+import {StatementInput} from '../measurables/statement_input';
+import {TopRow} from '../measurables/top_row';
+import {Types} from '../measurables/types';
 
-import {ConstantProvider} from './constants.js';
-import * as debug from './debug.js';
-import {Debug} from './debugger.js';
-import {Drawer} from './drawer.js';
-import {IPathObject} from './i_path_object.js';
-import {RenderInfo} from './info.js';
-import {MarkerSvg} from './marker_svg.js';
-import {PathObject} from './path_object.js';
-import {Renderer} from './renderer.js';
+import {ConstantProvider} from './constants';
+import * as debug from './debug';
+import {Debug} from './debugger';
+import {Drawer} from './drawer';
+import {IPathObject} from './i_path_object';
+import {RenderInfo} from './info';
+import {MarkerSvg} from './marker_svg';
+import {PathObject} from './path_object';
+import {Renderer} from './renderer';
 
 
 /**
diff --git a/core/renderers/common/constants.ts b/core/renderers/common/constants.ts
index e359a0127..98cab9f52 100644
--- a/core/renderers/common/constants.ts
+++ b/core/renderers/common/constants.ts
@@ -12,19 +12,19 @@
  * An object that provides constants for rendering blocks.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.ConstantProvider');
 
-import {ConnectionType} from '../../connection_type.js';
+import {ConnectionType} from '../../connection_type';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
-import {BlockStyle, Theme} from '../../theme.js';
-import * as colour from '../../utils/colour.js';
-import * as dom from '../../utils/dom.js';
-import * as parsing from '../../utils/parsing.js';
-import {Svg} from '../../utils/svg.js';
-import * as svgPaths from '../../utils/svg_paths.js';
-import * as userAgent from '../../utils/useragent.js';
+import {RenderedConnection} from '../../rendered_connection';
+import {BlockStyle, Theme} from '../../theme';
+import * as colour from '../../utils/colour';
+import * as dom from '../../utils/dom';
+import * as parsing from '../../utils/parsing';
+import {Svg} from '../../utils/svg';
+import * as svgPaths from '../../utils/svg_paths';
+import * as userAgent from '../../utils/useragent';
 
 
 /** An object containing sizing and path information about outside corners. */
diff --git a/core/renderers/common/debug.ts b/core/renderers/common/debug.ts
index 7b4407fde..fa1d0635d 100644
--- a/core/renderers/common/debug.ts
+++ b/core/renderers/common/debug.ts
@@ -12,10 +12,10 @@
  * Block rendering debugging functionality.
  * @namespace Blockly.blockRendering.debug
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.debug');
 
-import * as deprecation from '../../utils/deprecation.js';
+import * as deprecation from '../../utils/deprecation';
 
 
 /** Whether or not the debugger is turned on. */
diff --git a/core/renderers/common/debugger.ts b/core/renderers/common/debugger.ts
index c23d829e8..fcd4d0cff 100644
--- a/core/renderers/common/debugger.ts
+++ b/core/renderers/common/debugger.ts
@@ -12,33 +12,33 @@
  * Methods for rendering debug graphics.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Debug');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {ConnectionType} from '../../connection_type.js';
-import {FieldLabel} from '../../field_label.js';
+import {BlockSvg} from '../../block_svg';
+import {ConnectionType} from '../../connection_type';
+import {FieldLabel} from '../../field_label';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
-import * as dom from '../../utils/dom.js';
-import {Svg} from '../../utils/svg.js';
+import {RenderedConnection} from '../../rendered_connection';
+import * as dom from '../../utils/dom';
+import {Svg} from '../../utils/svg';
 /* eslint-disable-next-line no-unused-vars */
-import {Measurable} from '../measurables/base.js';
-import {Field} from '../measurables/field.js';
+import {Measurable} from '../measurables/base';
+import {Field} from '../measurables/field';
 /* eslint-disable-next-line no-unused-vars */
-import {InRowSpacer} from '../measurables/in_row_spacer.js';
-import {InputConnection} from '../measurables/input_connection.js';
+import {InRowSpacer} from '../measurables/in_row_spacer';
+import {InputConnection} from '../measurables/input_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {Row} from '../measurables/row.js';
-import {Types} from '../measurables/types.js';
+import {Row} from '../measurables/row';
+import {Types} from '../measurables/types';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo as ZelosInfo} from '../zelos/info.js';
+import {RenderInfo as ZelosInfo} from '../zelos/info';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from './constants.js';
+import {ConstantProvider} from './constants';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo} from './info.js';
+import {RenderInfo} from './info';
 
 
 /**
diff --git a/core/renderers/common/drawer.ts b/core/renderers/common/drawer.ts
index bfd83b42f..0278794ac 100644
--- a/core/renderers/common/drawer.ts
+++ b/core/renderers/common/drawer.ts
@@ -12,32 +12,32 @@
  * Methods for graphically rendering a block as SVG.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Drawer');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import * as svgPaths from '../../utils/svg_paths.js';
-import {Connection} from '../measurables/connection.js';
+import {BlockSvg} from '../../block_svg';
+import * as svgPaths from '../../utils/svg_paths';
+import {Connection} from '../measurables/connection';
 /* eslint-disable-next-line no-unused-vars */
-import {ExternalValueInput} from '../measurables/external_value_input.js';
+import {ExternalValueInput} from '../measurables/external_value_input';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from '../measurables/field.js';
+import {Field} from '../measurables/field';
 /* eslint-disable-next-line no-unused-vars */
-import {Icon} from '../measurables/icon.js';
+import {Icon} from '../measurables/icon';
 /* eslint-disable-next-line no-unused-vars */
-import {InlineInput} from '../measurables/inline_input.js';
+import {InlineInput} from '../measurables/inline_input';
 /* eslint-disable-next-line no-unused-vars */
-import {PreviousConnection} from '../measurables/previous_connection.js';
+import {PreviousConnection} from '../measurables/previous_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {Row} from '../measurables/row.js';
-import {Types} from '../measurables/types.js';
+import {Row} from '../measurables/row';
+import {Types} from '../measurables/types';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider, Notch, PuzzleTab} from './constants.js';
-import * as debug from './debug.js';
+import {ConstantProvider, Notch, PuzzleTab} from './constants';
+import * as debug from './debug';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo} from './info.js';
+import {RenderInfo} from './info';
 
 
 /**
diff --git a/core/renderers/common/i_path_object.ts b/core/renderers/common/i_path_object.ts
index de57cbff0..f454e9347 100644
--- a/core/renderers/common/i_path_object.ts
+++ b/core/renderers/common/i_path_object.ts
@@ -14,23 +14,23 @@
  * elements.
  * @namespace Blockly.blockRendering.IPathObject
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.IPathObject');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../../block_svg.js';
+import '../../block_svg';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../../connection.js';
+import '../../connection';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../../theme.js';
+import '../../theme';
 
-import {BlockStyle} from '../../theme.js';
+import {BlockStyle} from '../../theme';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from './constants.js';
+import {ConstantProvider} from './constants';
 
 
 /**
diff --git a/core/renderers/common/info.ts b/core/renderers/common/info.ts
index 24fe1e30f..77e36de89 100644
--- a/core/renderers/common/info.ts
+++ b/core/renderers/common/info.ts
@@ -12,42 +12,42 @@
  * Methods for graphically rendering a block as SVG.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.RenderInfo');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {Align, Input} from '../../input.js';
-import {inputTypes} from '../../input_types.js';
+import {BlockSvg} from '../../block_svg';
+import {Align, Input} from '../../input';
+import {inputTypes} from '../../input_types';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
+import {RenderedConnection} from '../../rendered_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {Measurable} from '../measurables/base.js';
-import {BottomRow} from '../measurables/bottom_row.js';
-import {ExternalValueInput} from '../measurables/external_value_input.js';
-import {Field} from '../measurables/field.js';
-import {Hat} from '../measurables/hat.js';
-import {Icon} from '../measurables/icon.js';
-import {InRowSpacer} from '../measurables/in_row_spacer.js';
-import {InlineInput} from '../measurables/inline_input.js';
-import {InputRow} from '../measurables/input_row.js';
-import {JaggedEdge} from '../measurables/jagged_edge.js';
-import {NextConnection} from '../measurables/next_connection.js';
-import {OutputConnection} from '../measurables/output_connection.js';
-import {PreviousConnection} from '../measurables/previous_connection.js';
-import {RoundCorner} from '../measurables/round_corner.js';
+import {Measurable} from '../measurables/base';
+import {BottomRow} from '../measurables/bottom_row';
+import {ExternalValueInput} from '../measurables/external_value_input';
+import {Field} from '../measurables/field';
+import {Hat} from '../measurables/hat';
+import {Icon} from '../measurables/icon';
+import {InRowSpacer} from '../measurables/in_row_spacer';
+import {InlineInput} from '../measurables/inline_input';
+import {InputRow} from '../measurables/input_row';
+import {JaggedEdge} from '../measurables/jagged_edge';
+import {NextConnection} from '../measurables/next_connection';
+import {OutputConnection} from '../measurables/output_connection';
+import {PreviousConnection} from '../measurables/previous_connection';
+import {RoundCorner} from '../measurables/round_corner';
 /* eslint-disable-next-line no-unused-vars */
-import {Row} from '../measurables/row.js';
-import {SpacerRow} from '../measurables/spacer_row.js';
-import {SquareCorner} from '../measurables/square_corner.js';
-import {StatementInput} from '../measurables/statement_input.js';
-import {TopRow} from '../measurables/top_row.js';
-import {Types} from '../measurables/types.js';
+import {Row} from '../measurables/row';
+import {SpacerRow} from '../measurables/spacer_row';
+import {SquareCorner} from '../measurables/square_corner';
+import {StatementInput} from '../measurables/statement_input';
+import {TopRow} from '../measurables/top_row';
+import {Types} from '../measurables/types';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from './constants.js';
+import {ConstantProvider} from './constants';
 /* eslint-disable-next-line no-unused-vars */
-import {Renderer} from './renderer.js';
+import {Renderer} from './renderer';
 
 
 /**
diff --git a/core/renderers/common/marker_svg.ts b/core/renderers/common/marker_svg.ts
index 1d7ffdf2c..4797c3838 100644
--- a/core/renderers/common/marker_svg.ts
+++ b/core/renderers/common/marker_svg.ts
@@ -12,35 +12,35 @@
  * Methods for graphically rendering a marker as SVG.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.MarkerSvg');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../../events/events_marker_move.js';
+import '../../events/events_marker_move';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
+import {BlockSvg} from '../../block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {Connection} from '../../connection.js';
-import {ConnectionType} from '../../connection_type.js';
-import * as eventUtils from '../../events/utils.js';
+import {Connection} from '../../connection';
+import {ConnectionType} from '../../connection_type';
+import * as eventUtils from '../../events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from '../../field.js';
+import {Field} from '../../field';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocationSvg} from '../../interfaces/i_ast_node_location_svg.js';
-import {ASTNode} from '../../keyboard_nav/ast_node.js';
+import {IASTNodeLocationSvg} from '../../interfaces/i_ast_node_location_svg';
+import {ASTNode} from '../../keyboard_nav/ast_node';
 /* eslint-disable-next-line no-unused-vars */
-import {Marker} from '../../keyboard_nav/marker.js';
+import {Marker} from '../../keyboard_nav/marker';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
-import * as dom from '../../utils/dom.js';
-import {Svg} from '../../utils/svg.js';
-import * as svgPaths from '../../utils/svg_paths.js';
+import {RenderedConnection} from '../../rendered_connection';
+import * as dom from '../../utils/dom';
+import {Svg} from '../../utils/svg';
+import * as svgPaths from '../../utils/svg_paths';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../../workspace_svg.js';
+import {WorkspaceSvg} from '../../workspace_svg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider, Notch, PuzzleTab} from './constants.js';
+import {ConstantProvider, Notch, PuzzleTab} from './constants';
 
 
 /** The name of the CSS class for a cursor. */
diff --git a/core/renderers/common/path_object.ts b/core/renderers/common/path_object.ts
index ed002ce25..79fb6f71f 100644
--- a/core/renderers/common/path_object.ts
+++ b/core/renderers/common/path_object.ts
@@ -12,25 +12,25 @@
  * An object that owns a block's rendering SVG elements.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.PathObject');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../../theme.js';
+import '../../theme';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
+import {BlockSvg} from '../../block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {Connection} from '../../connection.js';
-import {BlockStyle} from '../../theme.js';
-import * as dom from '../../utils/dom.js';
-import {Svg} from '../../utils/svg.js';
+import {Connection} from '../../connection';
+import {BlockStyle} from '../../theme';
+import * as dom from '../../utils/dom';
+import {Svg} from '../../utils/svg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from './constants.js';
+import {ConstantProvider} from './constants';
 /* eslint-disable-next-line no-unused-vars */
-import {IPathObject} from './i_path_object.js';
+import {IPathObject} from './i_path_object';
 
 
 /**
diff --git a/core/renderers/common/renderer.ts b/core/renderers/common/renderer.ts
index b8839dcbf..86e9639e8 100644
--- a/core/renderers/common/renderer.ts
+++ b/core/renderers/common/renderer.ts
@@ -12,36 +12,36 @@
  * Base renderer.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Renderer');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../../block.js';
+import {Block} from '../../block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {Connection} from '../../connection.js';
-import {ConnectionType} from '../../connection_type.js';
-import {InsertionMarkerManager, PreviewType} from '../../insertion_marker_manager.js';
+import {BlockSvg} from '../../block_svg';
+import {Connection} from '../../connection';
+import {ConnectionType} from '../../connection_type';
+import {InsertionMarkerManager, PreviewType} from '../../insertion_marker_manager';
 /* eslint-disable-next-line no-unused-vars */
-import {IRegistrable} from '../../interfaces/i_registrable.js';
+import {IRegistrable} from '../../interfaces/i_registrable';
 /* eslint-disable-next-line no-unused-vars */
-import {Marker} from '../../keyboard_nav/marker.js';
+import {Marker} from '../../keyboard_nav/marker';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
-import {BlockStyle, Theme} from '../../theme.js';
+import {RenderedConnection} from '../../rendered_connection';
+import {BlockStyle, Theme} from '../../theme';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../../workspace_svg.js';
+import {WorkspaceSvg} from '../../workspace_svg';
 
-import {ConstantProvider} from './constants.js';
-import * as debug from './debug.js';
+import {ConstantProvider} from './constants';
+import * as debug from './debug';
 /* eslint-disable-next-line no-unused-vars */
-import {Debug} from './debugger.js';
-import {Drawer} from './drawer.js';
+import {Debug} from './debugger';
+import {Drawer} from './drawer';
 /* eslint-disable-next-line no-unused-vars */
-import {IPathObject} from './i_path_object.js';
-import {RenderInfo} from './info.js';
-import {MarkerSvg} from './marker_svg.js';
-import {PathObject} from './path_object.js';
+import {IPathObject} from './i_path_object';
+import {RenderInfo} from './info';
+import {MarkerSvg} from './marker_svg';
+import {PathObject} from './path_object';
 
 
 /**
diff --git a/core/renderers/geras/constants.ts b/core/renderers/geras/constants.ts
index d4f997a41..77869cfa5 100644
--- a/core/renderers/geras/constants.ts
+++ b/core/renderers/geras/constants.ts
@@ -14,10 +14,10 @@
  * mode.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras.ConstantProvider');
 
-import {ConstantProvider as BaseConstantProvider} from '../common/constants.js';
+import {ConstantProvider as BaseConstantProvider} from '../common/constants';
 
 
 /**
diff --git a/core/renderers/geras/drawer.ts b/core/renderers/geras/drawer.ts
index 1867735b6..c80bb684d 100644
--- a/core/renderers/geras/drawer.ts
+++ b/core/renderers/geras/drawer.ts
@@ -12,25 +12,25 @@
  * Renderer that preserves the look and feel of Blockly pre-2019.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras.Drawer');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import * as svgPaths from '../../utils/svg_paths.js';
-import * as debug from '../common/debug.js';
-import {Drawer as BaseDrawer} from '../common/drawer.js';
-import {Row} from '../measurables/row.js';
+import {BlockSvg} from '../../block_svg';
+import * as svgPaths from '../../utils/svg_paths';
+import * as debug from '../common/debug';
+import {Drawer as BaseDrawer} from '../common/drawer';
+import {Row} from '../measurables/row';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from './constants.js';
-import {Highlighter} from './highlighter.js';
+import {ConstantProvider} from './constants';
+import {Highlighter} from './highlighter';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo} from './info.js';
+import {RenderInfo} from './info';
 /* eslint-disable-next-line no-unused-vars */
-import {InlineInput} from './measurables/inline_input.js';
+import {InlineInput} from './measurables/inline_input';
 /* eslint-disable-next-line no-unused-vars */
-import {PathObject} from './path_object.js';
+import {PathObject} from './path_object';
 
 
 /**
diff --git a/core/renderers/geras/geras.ts b/core/renderers/geras/geras.ts
index 3840f534f..41e85ae9c 100644
--- a/core/renderers/geras/geras.ts
+++ b/core/renderers/geras/geras.ts
@@ -10,18 +10,18 @@
  * Re-exports of Blockly.geras.* modules.
  * @namespace Blockly.geras
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras');
 
-import {ConstantProvider} from './constants.js';
-import {Drawer} from './drawer.js';
-import {HighlightConstantProvider} from './highlight_constants.js';
-import {Highlighter} from './highlighter.js';
-import {RenderInfo} from './info.js';
-import {InlineInput} from './measurables/inline_input.js';
-import {StatementInput} from './measurables/statement_input.js';
-import {PathObject} from './path_object.js';
-import {Renderer} from './renderer.js';
+import {ConstantProvider} from './constants';
+import {Drawer} from './drawer';
+import {HighlightConstantProvider} from './highlight_constants';
+import {Highlighter} from './highlighter';
+import {RenderInfo} from './info';
+import {InlineInput} from './measurables/inline_input';
+import {StatementInput} from './measurables/statement_input';
+import {PathObject} from './path_object';
+import {Renderer} from './renderer';
 
 
 export {
diff --git a/core/renderers/geras/highlight_constants.ts b/core/renderers/geras/highlight_constants.ts
index 8f7d8fb32..0e6c88d51 100644
--- a/core/renderers/geras/highlight_constants.ts
+++ b/core/renderers/geras/highlight_constants.ts
@@ -12,12 +12,12 @@
  * Objects for rendering highlights on blocks.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras.HighlightConstantProvider');
 
-import * as svgPaths from '../../utils/svg_paths.js';
+import * as svgPaths from '../../utils/svg_paths';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
 
 /** An object containing sizing and path information about an outside corner. */
diff --git a/core/renderers/geras/highlighter.ts b/core/renderers/geras/highlighter.ts
index 27a12aa33..2afc20f42 100644
--- a/core/renderers/geras/highlighter.ts
+++ b/core/renderers/geras/highlighter.ts
@@ -14,30 +14,30 @@
  * compatibility mode.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras.Highlighter');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './renderer.js';
+import './renderer';
 
-import * as svgPaths from '../../utils/svg_paths.js';
+import * as svgPaths from '../../utils/svg_paths';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 /* eslint-disable-next-line no-unused-vars */
-import {BottomRow} from '../measurables/bottom_row.js';
+import {BottomRow} from '../measurables/bottom_row';
 /* eslint-disable-next-line no-unused-vars */
-import {Row} from '../measurables/row.js';
-import {SpacerRow} from '../measurables/spacer_row.js';
+import {Row} from '../measurables/row';
+import {SpacerRow} from '../measurables/spacer_row';
 /* eslint-disable-next-line no-unused-vars */
-import {TopRow} from '../measurables/top_row.js';
-import {Types} from '../measurables/types.js';
+import {TopRow} from '../measurables/top_row';
+import {Types} from '../measurables/types';
 
-import {HighlightConstantProvider, InsideCorner, JaggedTeeth, Notch, OutsideCorner, PuzzleTab, StartHat} from './highlight_constants.js';
+import {HighlightConstantProvider, InsideCorner, JaggedTeeth, Notch, OutsideCorner, PuzzleTab, StartHat} from './highlight_constants';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo} from './info.js';
+import {RenderInfo} from './info';
 /* eslint-disable-next-line no-unused-vars */
-import {InlineInput} from './measurables/inline_input.js';
+import {InlineInput} from './measurables/inline_input';
 
 
 /**
diff --git a/core/renderers/geras/info.ts b/core/renderers/geras/info.ts
index 850303fa6..1a3cf4f00 100644
--- a/core/renderers/geras/info.ts
+++ b/core/renderers/geras/info.ts
@@ -14,34 +14,34 @@
  * Geras: spirit of old age.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras.RenderInfo');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {Input} from '../../input.js';
-import {inputTypes} from '../../input_types.js';
-import {RenderInfo as BaseRenderInfo} from '../common/info.js';
-import {Measurable} from '../measurables/base.js';
+import {BlockSvg} from '../../block_svg';
+import {Input} from '../../input';
+import {inputTypes} from '../../input_types';
+import {RenderInfo as BaseRenderInfo} from '../common/info';
+import {Measurable} from '../measurables/base';
 /* eslint-disable-next-line no-unused-vars */
-import {BottomRow} from '../measurables/bottom_row.js';
-import {ExternalValueInput} from '../measurables/external_value_input.js';
+import {BottomRow} from '../measurables/bottom_row';
+import {ExternalValueInput} from '../measurables/external_value_input';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from '../measurables/field.js';
-import {InRowSpacer} from '../measurables/in_row_spacer.js';
+import {Field} from '../measurables/field';
+import {InRowSpacer} from '../measurables/in_row_spacer';
 /* eslint-disable-next-line no-unused-vars */
-import {InputRow} from '../measurables/input_row.js';
-import {Row} from '../measurables/row.js';
+import {InputRow} from '../measurables/input_row';
+import {Row} from '../measurables/row';
 /* eslint-disable-next-line no-unused-vars */
-import {TopRow} from '../measurables/top_row.js';
-import {Types} from '../measurables/types.js';
+import {TopRow} from '../measurables/top_row';
+import {Types} from '../measurables/types';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from './constants.js';
-import {InlineInput} from './measurables/inline_input.js';
-import {StatementInput} from './measurables/statement_input.js';
+import {ConstantProvider} from './constants';
+import {InlineInput} from './measurables/inline_input';
+import {StatementInput} from './measurables/statement_input';
 /* eslint-disable-next-line no-unused-vars */
-import {Renderer} from './renderer.js';
+import {Renderer} from './renderer';
 
 
 /**
diff --git a/core/renderers/geras/measurables/inline_input.ts b/core/renderers/geras/measurables/inline_input.ts
index 01c5fb21a..072dca1f6 100644
--- a/core/renderers/geras/measurables/inline_input.ts
+++ b/core/renderers/geras/measurables/inline_input.ts
@@ -14,16 +14,16 @@
  * rendered block.
  * @class
  */
-import * as goog from '../../../../closure/goog/goog.js';
+import * as goog from '../../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras.InlineInput');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from '../../../input.js';
-import {ConstantProvider as BaseConstantProvider} from '../../../renderers/common/constants.js';
-import {InlineInput as BaseInlineInput} from '../../../renderers/measurables/inline_input.js';
+import {Input} from '../../../input';
+import {ConstantProvider as BaseConstantProvider} from '../../../renderers/common/constants';
+import {InlineInput as BaseInlineInput} from '../../../renderers/measurables/inline_input';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider as GerasConstantProvider} from '../constants.js';
+import {ConstantProvider as GerasConstantProvider} from '../constants';
 
 
 /**
diff --git a/core/renderers/geras/measurables/statement_input.ts b/core/renderers/geras/measurables/statement_input.ts
index 1b9f5467c..f609f048e 100644
--- a/core/renderers/geras/measurables/statement_input.ts
+++ b/core/renderers/geras/measurables/statement_input.ts
@@ -14,16 +14,16 @@
  * rendered block.
  * @class
  */
-import * as goog from '../../../../closure/goog/goog.js';
+import * as goog from '../../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras.StatementInput');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from '../../../input.js';
-import {ConstantProvider as BaseConstantProvider} from '../../../renderers/common/constants.js';
-import {StatementInput as BaseStatementInput} from '../../../renderers/measurables/statement_input.js';
+import {Input} from '../../../input';
+import {ConstantProvider as BaseConstantProvider} from '../../../renderers/common/constants';
+import {StatementInput as BaseStatementInput} from '../../../renderers/measurables/statement_input';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider as GerasConstantProvider} from '../constants.js';
+import {ConstantProvider as GerasConstantProvider} from '../constants';
 
 
 /**
diff --git a/core/renderers/geras/path_object.ts b/core/renderers/geras/path_object.ts
index 857b665e6..cbada8735 100644
--- a/core/renderers/geras/path_object.ts
+++ b/core/renderers/geras/path_object.ts
@@ -12,22 +12,22 @@
  * An object that owns a block's rendering SVG elements.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras.PathObject');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../../theme.js';
+import '../../theme';
 
-import {BlockSvg} from '../../block_svg.js';
-import {BlockStyle} from '../../theme.js';
-import * as colour from '../../utils/colour.js';
-import * as dom from '../../utils/dom.js';
-import {Svg} from '../../utils/svg.js';
-import {PathObject as BasePathObject} from '../common/path_object.js';
+import {BlockSvg} from '../../block_svg';
+import {BlockStyle} from '../../theme';
+import * as colour from '../../utils/colour';
+import * as dom from '../../utils/dom';
+import {Svg} from '../../utils/svg';
+import {PathObject as BasePathObject} from '../common/path_object';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from './constants.js';
+import {ConstantProvider} from './constants';
 
 
 /**
diff --git a/core/renderers/geras/renderer.ts b/core/renderers/geras/renderer.ts
index 64cc57b13..b8e217b87 100644
--- a/core/renderers/geras/renderer.ts
+++ b/core/renderers/geras/renderer.ts
@@ -12,26 +12,26 @@
  * Geras renderer.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.geras.Renderer');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../common/constants.js';
+import '../common/constants';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {BlockStyle, Theme} from '../../theme.js';
-import * as blockRendering from '../common/block_rendering.js';
+import {BlockSvg} from '../../block_svg';
+import {BlockStyle, Theme} from '../../theme';
+import * as blockRendering from '../common/block_rendering';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo as BaseRenderInfo} from '../common/info.js';
-import {Renderer as BaseRenderer} from '../common/renderer.js';
+import {RenderInfo as BaseRenderInfo} from '../common/info';
+import {Renderer as BaseRenderer} from '../common/renderer';
 
-import {ConstantProvider} from './constants.js';
-import {Drawer} from './drawer.js';
-import {HighlightConstantProvider} from './highlight_constants.js';
-import {RenderInfo} from './info.js';
-import {PathObject} from './path_object.js';
+import {ConstantProvider} from './constants';
+import {Drawer} from './drawer';
+import {HighlightConstantProvider} from './highlight_constants';
+import {RenderInfo} from './info';
+import {PathObject} from './path_object';
 
 
 /**
diff --git a/core/renderers/measurables/base.ts b/core/renderers/measurables/base.ts
index ab91053d2..80a53e5e3 100644
--- a/core/renderers/measurables/base.ts
+++ b/core/renderers/measurables/base.ts
@@ -12,13 +12,13 @@
  * Methods for graphically rendering a block as SVG.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Measurable');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Types} from './types.js';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/bottom_row.ts b/core/renderers/measurables/bottom_row.ts
index 81c717449..d196499f4 100644
--- a/core/renderers/measurables/bottom_row.ts
+++ b/core/renderers/measurables/bottom_row.ts
@@ -14,18 +14,18 @@
  * of its subcomponents.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.BottomRow');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
+import {BlockSvg} from '../../block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
 /* eslint-disable-next-line no-unused-vars */
-import {NextConnection} from './next_connection.js';
-import {Row} from './row.js';
-import {Types} from './types.js';
+import {NextConnection} from './next_connection';
+import {Row} from './row';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/connection.ts b/core/renderers/measurables/connection.ts
index 915a9b89f..77016a263 100644
--- a/core/renderers/measurables/connection.ts
+++ b/core/renderers/measurables/connection.ts
@@ -14,16 +14,16 @@
  * rendering.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Connection');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
-import {ConstantProvider, Shape} from '../common/constants.js';
+import {RenderedConnection} from '../../rendered_connection';
+import {ConstantProvider, Shape} from '../common/constants';
 
-import {Measurable} from './base.js';
-import {Types} from './types.js';
+import {Measurable} from './base';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/external_value_input.ts b/core/renderers/measurables/external_value_input.ts
index b1884b07e..d2af6862d 100644
--- a/core/renderers/measurables/external_value_input.ts
+++ b/core/renderers/measurables/external_value_input.ts
@@ -14,16 +14,16 @@
  * rendered block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.ExternalValueInput');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from '../../input.js';
-import {ConstantProvider} from '../common/constants.js';
+import {Input} from '../../input';
+import {ConstantProvider} from '../common/constants';
 
-import {InputConnection} from './input_connection.js';
-import {Types} from './types.js';
+import {InputConnection} from './input_connection';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/field.ts b/core/renderers/measurables/field.ts
index fd3d25862..a287591a6 100644
--- a/core/renderers/measurables/field.ts
+++ b/core/renderers/measurables/field.ts
@@ -14,18 +14,18 @@
  * block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Field');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {Field as BlocklyField} from '../../field.js';
+import {Field as BlocklyField} from '../../field';
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from '../../input.js';
-import {ConstantProvider} from '../common/constants.js';
+import {Input} from '../../input';
+import {ConstantProvider} from '../common/constants';
 
-import {Measurable} from './base.js';
-import {Types} from './types.js';
+import {Measurable} from './base';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/hat.ts b/core/renderers/measurables/hat.ts
index 43bb799bf..7795413d6 100644
--- a/core/renderers/measurables/hat.ts
+++ b/core/renderers/measurables/hat.ts
@@ -14,14 +14,14 @@
  * block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Hat');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Measurable} from './base.js';
-import {Types} from './types.js';
+import {Measurable} from './base';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/icon.ts b/core/renderers/measurables/icon.ts
index ad1fea58f..ac8dfdb2b 100644
--- a/core/renderers/measurables/icon.ts
+++ b/core/renderers/measurables/icon.ts
@@ -14,16 +14,16 @@
  * block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Icon');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {Icon as BlocklyIcon} from '../../icon.js';
-import {ConstantProvider} from '../common/constants.js';
+import {Icon as BlocklyIcon} from '../../icon';
+import {ConstantProvider} from '../common/constants';
 
-import {Measurable} from './base.js';
-import {Types} from './types.js';
+import {Measurable} from './base';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/in_row_spacer.ts b/core/renderers/measurables/in_row_spacer.ts
index 10685b6ca..3c9ce50f6 100644
--- a/core/renderers/measurables/in_row_spacer.ts
+++ b/core/renderers/measurables/in_row_spacer.ts
@@ -14,14 +14,14 @@
  * block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.InRowSpacer');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Measurable} from './base.js';
-import {Types} from './types.js';
+import {Measurable} from './base';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/inline_input.ts b/core/renderers/measurables/inline_input.ts
index 9be2a1572..5bba08125 100644
--- a/core/renderers/measurables/inline_input.ts
+++ b/core/renderers/measurables/inline_input.ts
@@ -14,16 +14,16 @@
  * block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.InlineInput');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from '../../input.js';
-import {ConstantProvider} from '../common/constants.js';
+import {Input} from '../../input';
+import {ConstantProvider} from '../common/constants';
 
-import {InputConnection} from './input_connection.js';
-import {Types} from './types.js';
+import {InputConnection} from './input_connection';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/input_connection.ts b/core/renderers/measurables/input_connection.ts
index 659df3ab4..e85ef3596 100644
--- a/core/renderers/measurables/input_connection.ts
+++ b/core/renderers/measurables/input_connection.ts
@@ -12,20 +12,20 @@
  * Class representing inputs with connections on a rendered block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.InputConnection');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
+import {BlockSvg} from '../../block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from '../../input.js';
+import {Input} from '../../input';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
+import {RenderedConnection} from '../../rendered_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Connection} from './connection.js';
-import {Types} from './types.js';
+import {Connection} from './connection';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/input_row.ts b/core/renderers/measurables/input_row.ts
index 3adaa174c..8a726654c 100644
--- a/core/renderers/measurables/input_row.ts
+++ b/core/renderers/measurables/input_row.ts
@@ -14,17 +14,17 @@
  * rendered block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.InputRow');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {ExternalValueInput} from './external_value_input.js';
-import {InputConnection} from './input_connection.js';
-import {Row} from './row.js';
-import {StatementInput} from './statement_input.js';
-import {Types} from './types.js';
+import {ExternalValueInput} from './external_value_input';
+import {InputConnection} from './input_connection';
+import {Row} from './row';
+import {StatementInput} from './statement_input';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/jagged_edge.ts b/core/renderers/measurables/jagged_edge.ts
index ec0f1444e..99df7e373 100644
--- a/core/renderers/measurables/jagged_edge.ts
+++ b/core/renderers/measurables/jagged_edge.ts
@@ -14,14 +14,14 @@
  * block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.JaggedEdge');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Measurable} from './base.js';
-import {Types} from './types.js';
+import {Measurable} from './base';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/next_connection.ts b/core/renderers/measurables/next_connection.ts
index 05238eb65..131ee075e 100644
--- a/core/renderers/measurables/next_connection.ts
+++ b/core/renderers/measurables/next_connection.ts
@@ -14,16 +14,16 @@
  * rendering.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.NextConnection');
 
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
+import {RenderedConnection} from '../../rendered_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Connection} from './connection.js';
-import {Types} from './types.js';
+import {Connection} from './connection';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/output_connection.ts b/core/renderers/measurables/output_connection.ts
index ac9e4212d..7e4f25745 100644
--- a/core/renderers/measurables/output_connection.ts
+++ b/core/renderers/measurables/output_connection.ts
@@ -14,16 +14,16 @@
  * during rendering.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.OutputConnection');
 
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
+import {RenderedConnection} from '../../rendered_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Connection} from './connection.js';
-import {Types} from './types.js';
+import {Connection} from './connection';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/previous_connection.ts b/core/renderers/measurables/previous_connection.ts
index 5fe9d5a88..0fa048a28 100644
--- a/core/renderers/measurables/previous_connection.ts
+++ b/core/renderers/measurables/previous_connection.ts
@@ -14,16 +14,16 @@
  * during rendering.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.PreviousConnection');
 
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
+import {RenderedConnection} from '../../rendered_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Connection} from './connection.js';
-import {Types} from './types.js';
+import {Connection} from './connection';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/round_corner.ts b/core/renderers/measurables/round_corner.ts
index 1c1ff3151..4cb3b9bb0 100644
--- a/core/renderers/measurables/round_corner.ts
+++ b/core/renderers/measurables/round_corner.ts
@@ -14,14 +14,14 @@
  * block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.RoundCorner');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Measurable} from './base.js';
-import {Types} from './types.js';
+import {Measurable} from './base';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/row.ts b/core/renderers/measurables/row.ts
index 74a723898..e3e367043 100644
--- a/core/renderers/measurables/row.ts
+++ b/core/renderers/measurables/row.ts
@@ -12,19 +12,19 @@
  * Object representing a single row on a rendered block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Row');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Measurable} from './base.js';
+import {Measurable} from './base';
 /* eslint-disable-next-line no-unused-vars */
-import {InRowSpacer} from './in_row_spacer.js';
+import {InRowSpacer} from './in_row_spacer';
 /* eslint-disable-next-line no-unused-vars */
-import {InputConnection} from './input_connection.js';
-import {Types} from './types.js';
+import {InputConnection} from './input_connection';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/spacer_row.ts b/core/renderers/measurables/spacer_row.ts
index a84d905a6..e4812cba2 100644
--- a/core/renderers/measurables/spacer_row.ts
+++ b/core/renderers/measurables/spacer_row.ts
@@ -12,15 +12,15 @@
  * Object representing a spacer between two rows.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.SpacerRow');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {InRowSpacer} from './in_row_spacer.js';
-import {Row} from './row.js';
-import {Types} from './types.js';
+import {InRowSpacer} from './in_row_spacer';
+import {Row} from './row';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/square_corner.ts b/core/renderers/measurables/square_corner.ts
index 2e2b86985..212c65b1c 100644
--- a/core/renderers/measurables/square_corner.ts
+++ b/core/renderers/measurables/square_corner.ts
@@ -14,14 +14,14 @@
  * block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.SquareCorner');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Measurable} from './base.js';
-import {Types} from './types.js';
+import {Measurable} from './base';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/statement_input.ts b/core/renderers/measurables/statement_input.ts
index 99bb345da..09c523cc2 100644
--- a/core/renderers/measurables/statement_input.ts
+++ b/core/renderers/measurables/statement_input.ts
@@ -14,16 +14,16 @@
  * rendered block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.StatementInput');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from '../../input.js';
-import {ConstantProvider} from '../common/constants.js';
+import {Input} from '../../input';
+import {ConstantProvider} from '../common/constants';
 
-import {InputConnection} from './input_connection.js';
-import {Types} from './types.js';
+import {InputConnection} from './input_connection';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/top_row.ts b/core/renderers/measurables/top_row.ts
index 9a404d889..9895b0775 100644
--- a/core/renderers/measurables/top_row.ts
+++ b/core/renderers/measurables/top_row.ts
@@ -12,19 +12,19 @@
  * Object representing a top row on a rendered block.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.TopRow');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
+import {BlockSvg} from '../../block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../common/constants.js';
+import {ConstantProvider} from '../common/constants';
 
-import {Hat} from './hat.js';
+import {Hat} from './hat';
 /* eslint-disable-next-line no-unused-vars */
-import {PreviousConnection} from './previous_connection.js';
-import {Row} from './row.js';
-import {Types} from './types.js';
+import {PreviousConnection} from './previous_connection';
+import {Row} from './row';
+import {Types} from './types';
 
 
 /**
diff --git a/core/renderers/measurables/types.ts b/core/renderers/measurables/types.ts
index 67dfd049f..ef1f5406e 100644
--- a/core/renderers/measurables/types.ts
+++ b/core/renderers/measurables/types.ts
@@ -12,13 +12,13 @@
  * Measurable types.
  * @namespace Blockly.blockRendering.Types
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.blockRendering.Types');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Measurable} from './base.js';
+import {Measurable} from './base';
 /* eslint-disable-next-line no-unused-vars */
-import {Row} from './row.js';
+import {Row} from './row';
 
 
 /**
diff --git a/core/renderers/minimalist/constants.ts b/core/renderers/minimalist/constants.ts
index 2db269754..4fb1c2d46 100644
--- a/core/renderers/minimalist/constants.ts
+++ b/core/renderers/minimalist/constants.ts
@@ -14,10 +14,10 @@
  * minimalist renderer.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.minimalist.ConstantProvider');
 
-import {ConstantProvider as BaseConstantProvider} from '../common/constants.js';
+import {ConstantProvider as BaseConstantProvider} from '../common/constants';
 
 
 /**
diff --git a/core/renderers/minimalist/drawer.ts b/core/renderers/minimalist/drawer.ts
index 230d60aa2..8bc408895 100644
--- a/core/renderers/minimalist/drawer.ts
+++ b/core/renderers/minimalist/drawer.ts
@@ -12,15 +12,15 @@
  * Minimalist rendering drawer.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.minimalist.Drawer');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {Drawer as BaseDrawer} from '../common/drawer.js';
+import {BlockSvg} from '../../block_svg';
+import {Drawer as BaseDrawer} from '../common/drawer';
 
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo} from './info.js';
+import {RenderInfo} from './info';
 
 
 /**
diff --git a/core/renderers/minimalist/info.ts b/core/renderers/minimalist/info.ts
index 1256230a6..d8bc72d30 100644
--- a/core/renderers/minimalist/info.ts
+++ b/core/renderers/minimalist/info.ts
@@ -12,15 +12,15 @@
  * Minimalist render info object.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.minimalist.RenderInfo');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {RenderInfo as BaseRenderInfo} from '../common/info.js';
+import {BlockSvg} from '../../block_svg';
+import {RenderInfo as BaseRenderInfo} from '../common/info';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Renderer} from './renderer.js';
+import {Renderer} from './renderer';
 
 
 /**
diff --git a/core/renderers/minimalist/minimalist.ts b/core/renderers/minimalist/minimalist.ts
index a6f9dbcec..bce4687d2 100644
--- a/core/renderers/minimalist/minimalist.ts
+++ b/core/renderers/minimalist/minimalist.ts
@@ -10,13 +10,13 @@
  * Re-exports of Blockly.minimalist.* modules.
  * @namespace Blockly.minimalist
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.minimalist');
 
-import {ConstantProvider} from './constants.js';
-import {Drawer} from './drawer.js';
-import {RenderInfo} from './info.js';
-import {Renderer} from './renderer.js';
+import {ConstantProvider} from './constants';
+import {Drawer} from './drawer';
+import {RenderInfo} from './info';
+import {Renderer} from './renderer';
 
 
 export {ConstantProvider, Drawer, Renderer, RenderInfo};
diff --git a/core/renderers/minimalist/renderer.ts b/core/renderers/minimalist/renderer.ts
index 24c956b33..4379f347d 100644
--- a/core/renderers/minimalist/renderer.ts
+++ b/core/renderers/minimalist/renderer.ts
@@ -12,19 +12,19 @@
  * Minimalist renderer.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.minimalist.Renderer');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import * as blockRendering from '../common/block_rendering.js';
+import {BlockSvg} from '../../block_svg';
+import * as blockRendering from '../common/block_rendering';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo as BaseRenderInfo} from '../common/info.js';
-import {Renderer as BaseRenderer} from '../common/renderer.js';
+import {RenderInfo as BaseRenderInfo} from '../common/info';
+import {Renderer as BaseRenderer} from '../common/renderer';
 
-import {ConstantProvider} from './constants.js';
-import {Drawer} from './drawer.js';
-import {RenderInfo} from './info.js';
+import {ConstantProvider} from './constants';
+import {Drawer} from './drawer';
+import {RenderInfo} from './info';
 
 
 /**
diff --git a/core/renderers/thrasos/info.ts b/core/renderers/thrasos/info.ts
index 7168bf613..b2aadb6de 100644
--- a/core/renderers/thrasos/info.ts
+++ b/core/renderers/thrasos/info.ts
@@ -14,25 +14,25 @@
  * Thrasos: spirit of boldness.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.thrasos.RenderInfo');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {RenderInfo as BaseRenderInfo} from '../common/info.js';
-import {Measurable} from '../measurables/base.js';
+import {BlockSvg} from '../../block_svg';
+import {RenderInfo as BaseRenderInfo} from '../common/info';
+import {Measurable} from '../measurables/base';
 /* eslint-disable-next-line no-unused-vars */
-import {BottomRow} from '../measurables/bottom_row.js';
+import {BottomRow} from '../measurables/bottom_row';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from '../measurables/field.js';
-import {InRowSpacer} from '../measurables/in_row_spacer.js';
-import {Row} from '../measurables/row.js';
+import {Field} from '../measurables/field';
+import {InRowSpacer} from '../measurables/in_row_spacer';
+import {Row} from '../measurables/row';
 /* eslint-disable-next-line no-unused-vars */
-import {TopRow} from '../measurables/top_row.js';
-import {Types} from '../measurables/types.js';
+import {TopRow} from '../measurables/top_row';
+import {Types} from '../measurables/types';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Renderer} from './renderer.js';
+import {Renderer} from './renderer';
 
 
 /**
diff --git a/core/renderers/thrasos/renderer.ts b/core/renderers/thrasos/renderer.ts
index 7bacb9406..52704920e 100644
--- a/core/renderers/thrasos/renderer.ts
+++ b/core/renderers/thrasos/renderer.ts
@@ -12,15 +12,15 @@
  * Thrasos renderer.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.thrasos.Renderer');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import * as blockRendering from '../common/block_rendering.js';
-import {Renderer as BaseRenderer} from '../common/renderer.js';
+import {BlockSvg} from '../../block_svg';
+import * as blockRendering from '../common/block_rendering';
+import {Renderer as BaseRenderer} from '../common/renderer';
 
-import {RenderInfo} from './info.js';
+import {RenderInfo} from './info';
 
 
 /**
diff --git a/core/renderers/thrasos/thrasos.ts b/core/renderers/thrasos/thrasos.ts
index 2be08faff..ac30db11c 100644
--- a/core/renderers/thrasos/thrasos.ts
+++ b/core/renderers/thrasos/thrasos.ts
@@ -10,11 +10,11 @@
  * Re-exports of Blockly.thrasos.* modules.
  * @namespace Blockly.thrasos
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.thrasos');
 
-import {RenderInfo} from './info.js';
-import {Renderer} from './renderer.js';
+import {RenderInfo} from './info';
+import {Renderer} from './renderer';
 
 
 export {Renderer, RenderInfo};
diff --git a/core/renderers/zelos/constants.ts b/core/renderers/zelos/constants.ts
index ffba99ea5..2ff47ef4b 100644
--- a/core/renderers/zelos/constants.ts
+++ b/core/renderers/zelos/constants.ts
@@ -14,18 +14,18 @@
  * mode.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.ConstantProvider');
 
-import {ConnectionType} from '../../connection_type.js';
-import {RenderedConnection} from '../../rendered_connection.js';
-import {Theme} from '../../theme.js';
-import * as utilsColour from '../../utils/colour.js';
-import * as dom from '../../utils/dom.js';
-import {Svg} from '../../utils/svg.js';
-import * as svgPaths from '../../utils/svg_paths.js';
+import {ConnectionType} from '../../connection_type';
+import {RenderedConnection} from '../../rendered_connection';
+import {Theme} from '../../theme';
+import * as utilsColour from '../../utils/colour';
+import * as dom from '../../utils/dom';
+import {Svg} from '../../utils/svg';
+import * as svgPaths from '../../utils/svg_paths';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider as BaseConstantProvider, Shape} from '../common/constants.js';
+import {ConstantProvider as BaseConstantProvider, Shape} from '../common/constants';
 
 
 /** An object containing sizing and path information about inside corners. */
diff --git a/core/renderers/zelos/drawer.ts b/core/renderers/zelos/drawer.ts
index deb7f0d41..557b2226a 100644
--- a/core/renderers/zelos/drawer.ts
+++ b/core/renderers/zelos/drawer.ts
@@ -12,31 +12,31 @@
  * Zelos renderer.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.Drawer');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import * as svgPaths from '../../utils/svg_paths.js';
+import {BlockSvg} from '../../block_svg';
+import * as svgPaths from '../../utils/svg_paths';
 /* eslint-disable-next-line no-unused-vars */
-import {BaseShape, DynamicShape, Notch} from '../common/constants.js';
-import * as debug from '../common/debug.js';
-import {Drawer as BaseDrawer} from '../common/drawer.js';
-import {InlineInput} from '../measurables/inline_input.js';
+import {BaseShape, DynamicShape, Notch} from '../common/constants';
+import * as debug from '../common/debug';
+import {Drawer as BaseDrawer} from '../common/drawer';
+import {InlineInput} from '../measurables/inline_input';
 /* eslint-disable-next-line no-unused-vars */
-import {Row} from '../measurables/row.js';
+import {Row} from '../measurables/row';
 /* eslint-disable-next-line no-unused-vars */
-import {SpacerRow} from '../measurables/spacer_row.js';
-import {Types} from '../measurables/types.js';
+import {SpacerRow} from '../measurables/spacer_row';
+import {Types} from '../measurables/types';
 
 /* eslint-disable-next-line no-unused-vars */
-import {InsideCorners} from './constants.js';
+import {InsideCorners} from './constants';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo} from './info.js';
+import {RenderInfo} from './info';
 /* eslint-disable-next-line no-unused-vars */
-import {StatementInput} from './measurables/inputs.js';
+import {StatementInput} from './measurables/inputs';
 /* eslint-disable-next-line no-unused-vars */
-import {PathObject} from './path_object.js';
+import {PathObject} from './path_object';
 
 
 /**
diff --git a/core/renderers/zelos/info.ts b/core/renderers/zelos/info.ts
index ada9169d4..82e300ab8 100644
--- a/core/renderers/zelos/info.ts
+++ b/core/renderers/zelos/info.ts
@@ -13,39 +13,39 @@
  * Makecode/scratch-style renderer.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.RenderInfo');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {FieldImage} from '../../field_image.js';
-import {FieldLabel} from '../../field_label.js';
-import {FieldTextInput} from '../../field_textinput.js';
-import {Align, Input} from '../../input.js';
-import {inputTypes} from '../../input_types.js';
+import {BlockSvg} from '../../block_svg';
+import {FieldImage} from '../../field_image';
+import {FieldLabel} from '../../field_label';
+import {FieldTextInput} from '../../field_textinput';
+import {Align, Input} from '../../input';
+import {inputTypes} from '../../input_types';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo as BaseRenderInfo} from '../common/info.js';
+import {RenderInfo as BaseRenderInfo} from '../common/info';
 /* eslint-disable-next-line no-unused-vars */
-import {Measurable} from '../measurables/base.js';
-import {Field} from '../measurables/field.js';
-import {InRowSpacer} from '../measurables/in_row_spacer.js';
-import {InputConnection} from '../measurables/input_connection.js';
+import {Measurable} from '../measurables/base';
+import {Field} from '../measurables/field';
+import {InRowSpacer} from '../measurables/in_row_spacer';
+import {InputConnection} from '../measurables/input_connection';
 /* eslint-disable-next-line no-unused-vars */
-import {Row} from '../measurables/row.js';
+import {Row} from '../measurables/row';
 /* eslint-disable-next-line no-unused-vars */
-import {SpacerRow} from '../measurables/spacer_row.js';
-import {Types} from '../measurables/types.js';
+import {SpacerRow} from '../measurables/spacer_row';
+import {Types} from '../measurables/types';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider, InsideCorners} from './constants.js';
-import {BottomRow} from './measurables/bottom_row.js';
-import {StatementInput} from './measurables/inputs.js';
-import {RightConnectionShape} from './measurables/row_elements.js';
-import {TopRow} from './measurables/top_row.js';
+import {ConstantProvider, InsideCorners} from './constants';
+import {BottomRow} from './measurables/bottom_row';
+import {StatementInput} from './measurables/inputs';
+import {RightConnectionShape} from './measurables/row_elements';
+import {TopRow} from './measurables/top_row';
 /* eslint-disable-next-line no-unused-vars */
-import {PathObject} from './path_object.js';
+import {PathObject} from './path_object';
 /* eslint-disable-next-line no-unused-vars */
-import {Renderer} from './renderer.js';
+import {Renderer} from './renderer';
 
 
 /**
diff --git a/core/renderers/zelos/marker_svg.ts b/core/renderers/zelos/marker_svg.ts
index 767478eb3..9ca77e719 100644
--- a/core/renderers/zelos/marker_svg.ts
+++ b/core/renderers/zelos/marker_svg.ts
@@ -12,27 +12,27 @@
  * Methods for graphically rendering a marker as SVG.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.MarkerSvg');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
+import {BlockSvg} from '../../block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {ASTNode} from '../../keyboard_nav/ast_node.js';
+import {ASTNode} from '../../keyboard_nav/ast_node';
 /* eslint-disable-next-line no-unused-vars */
-import {Marker} from '../../keyboard_nav/marker.js';
+import {Marker} from '../../keyboard_nav/marker';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderedConnection} from '../../rendered_connection.js';
-import * as dom from '../../utils/dom.js';
-import {Svg} from '../../utils/svg.js';
+import {RenderedConnection} from '../../rendered_connection';
+import * as dom from '../../utils/dom';
+import {Svg} from '../../utils/svg';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../../workspace_svg.js';
+import {WorkspaceSvg} from '../../workspace_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider as BaseConstantProvider} from '../common/constants.js';
-import {MarkerSvg as BaseMarkerSvg} from '../common/marker_svg.js';
+import {ConstantProvider as BaseConstantProvider} from '../common/constants';
+import {MarkerSvg as BaseMarkerSvg} from '../common/marker_svg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider as ZelosConstantProvider} from './constants.js';
+import {ConstantProvider as ZelosConstantProvider} from './constants';
 
 
 /**
diff --git a/core/renderers/zelos/measurables/bottom_row.ts b/core/renderers/zelos/measurables/bottom_row.ts
index df0741281..94d9adb89 100644
--- a/core/renderers/zelos/measurables/bottom_row.ts
+++ b/core/renderers/zelos/measurables/bottom_row.ts
@@ -12,13 +12,13 @@
  * An object representing the bottom row of a rendered block.
  * @class
  */
-import * as goog from '../../../../closure/goog/goog.js';
+import * as goog from '../../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.BottomRow');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../../block_svg.js';
-import {ConstantProvider} from '../../../renderers/common/constants.js';
-import {BottomRow as BaseBottomRow} from '../../../renderers/measurables/bottom_row.js';
+import {BlockSvg} from '../../../block_svg';
+import {ConstantProvider} from '../../../renderers/common/constants';
+import {BottomRow as BaseBottomRow} from '../../../renderers/measurables/bottom_row';
 
 
 /**
diff --git a/core/renderers/zelos/measurables/inputs.ts b/core/renderers/zelos/measurables/inputs.ts
index e0e7fcea2..e0c8cc376 100644
--- a/core/renderers/zelos/measurables/inputs.ts
+++ b/core/renderers/zelos/measurables/inputs.ts
@@ -14,14 +14,14 @@
  * a rendered block.
  * @class
  */
-import * as goog from '../../../../closure/goog/goog.js';
+import * as goog from '../../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.StatementInput');
 
 /* eslint-disable-next-line no-unused-vars */
 /* eslint-disable-next-line no-unused-vars */
-import {Input} from '../../../input.js';
-import {ConstantProvider} from '../../../renderers/common/constants.js';
-import {StatementInput as BaseStatementInput} from '../../../renderers/measurables/statement_input.js';
+import {Input} from '../../../input';
+import {ConstantProvider} from '../../../renderers/common/constants';
+import {StatementInput as BaseStatementInput} from '../../../renderers/measurables/statement_input';
 
 
 /**
diff --git a/core/renderers/zelos/measurables/row_elements.ts b/core/renderers/zelos/measurables/row_elements.ts
index 78cc4f844..f054d75ea 100644
--- a/core/renderers/zelos/measurables/row_elements.ts
+++ b/core/renderers/zelos/measurables/row_elements.ts
@@ -14,13 +14,13 @@
  * rendered block.
  * @class
  */
-import * as goog from '../../../../closure/goog/goog.js';
+import * as goog from '../../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.RightConnectionShape');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from '../../../renderers/common/constants.js';
-import {Measurable} from '../../../renderers/measurables/base.js';
-import {Types} from '../../../renderers/measurables/types.js';
+import {ConstantProvider} from '../../../renderers/common/constants';
+import {Measurable} from '../../../renderers/measurables/base';
+import {Types} from '../../../renderers/measurables/types';
 
 
 /**
diff --git a/core/renderers/zelos/measurables/top_row.ts b/core/renderers/zelos/measurables/top_row.ts
index ad9ae9e37..9f1186216 100644
--- a/core/renderers/zelos/measurables/top_row.ts
+++ b/core/renderers/zelos/measurables/top_row.ts
@@ -12,13 +12,13 @@
  * An object representing the top row of a rendered block.
  * @class
  */
-import * as goog from '../../../../closure/goog/goog.js';
+import * as goog from '../../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.TopRow');
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../../block_svg.js';
-import {ConstantProvider} from '../../../renderers/common/constants.js';
-import {TopRow as BaseTopRow} from '../../../renderers/measurables/top_row.js';
+import {BlockSvg} from '../../../block_svg';
+import {ConstantProvider} from '../../../renderers/common/constants';
+import {TopRow as BaseTopRow} from '../../../renderers/measurables/top_row';
 
 
 /**
diff --git a/core/renderers/zelos/path_object.ts b/core/renderers/zelos/path_object.ts
index 1f73235be..1c8cb39bf 100644
--- a/core/renderers/zelos/path_object.ts
+++ b/core/renderers/zelos/path_object.ts
@@ -12,22 +12,22 @@
  * An object that owns a block's rendering SVG elements.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.PathObject');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../../theme.js';
+import '../../theme';
 
-import {BlockSvg} from '../../block_svg.js';
-import {Connection} from '../../connection.js';
-import {BlockStyle} from '../../theme.js';
-import * as dom from '../../utils/dom.js';
-import {Svg} from '../../utils/svg.js';
-import {PathObject as BasePathObject} from '../common/path_object.js';
+import {BlockSvg} from '../../block_svg';
+import {Connection} from '../../connection';
+import {BlockStyle} from '../../theme';
+import * as dom from '../../utils/dom';
+import {Svg} from '../../utils/svg';
+import {PathObject as BasePathObject} from '../common/path_object';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConstantProvider} from './constants.js';
+import {ConstantProvider} from './constants';
 
 
 /**
diff --git a/core/renderers/zelos/renderer.ts b/core/renderers/zelos/renderer.ts
index 6eff84757..ff6381dff 100644
--- a/core/renderers/zelos/renderer.ts
+++ b/core/renderers/zelos/renderer.ts
@@ -12,34 +12,34 @@
  * Zelos renderer.
  * @class
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos.Renderer');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../../theme.js';
+import '../../theme';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../../block_svg.js';
-import {Connection} from '../../connection.js';
-import {ConnectionType} from '../../connection_type.js';
-import {InsertionMarkerManager} from '../../insertion_marker_manager.js';
+import {BlockSvg} from '../../block_svg';
+import {Connection} from '../../connection';
+import {ConnectionType} from '../../connection_type';
+import {InsertionMarkerManager} from '../../insertion_marker_manager';
 /* eslint-disable-next-line no-unused-vars */
-import {Marker} from '../../keyboard_nav/marker.js';
-import {RenderedConnection} from '../../rendered_connection.js';
-import {BlockStyle} from '../../theme.js';
+import {Marker} from '../../keyboard_nav/marker';
+import {RenderedConnection} from '../../rendered_connection';
+import {BlockStyle} from '../../theme';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../../workspace_svg.js';
-import * as blockRendering from '../common/block_rendering.js';
+import {WorkspaceSvg} from '../../workspace_svg';
+import * as blockRendering from '../common/block_rendering';
 /* eslint-disable-next-line no-unused-vars */
-import {RenderInfo as BaseRenderInfo} from '../common/info.js';
-import {Renderer as BaseRenderer} from '../common/renderer.js';
+import {RenderInfo as BaseRenderInfo} from '../common/info';
+import {Renderer as BaseRenderer} from '../common/renderer';
 
-import {ConstantProvider} from './constants.js';
-import {Drawer} from './drawer.js';
-import {RenderInfo} from './info.js';
-import {MarkerSvg} from './marker_svg.js';
-import {PathObject} from './path_object.js';
+import {ConstantProvider} from './constants';
+import {Drawer} from './drawer';
+import {RenderInfo} from './info';
+import {MarkerSvg} from './marker_svg';
+import {PathObject} from './path_object';
 
 
 /**
diff --git a/core/renderers/zelos/zelos.ts b/core/renderers/zelos/zelos.ts
index 4158d3f5a..97963ce8f 100644
--- a/core/renderers/zelos/zelos.ts
+++ b/core/renderers/zelos/zelos.ts
@@ -10,19 +10,19 @@
  * Re-exports of Blockly.zelos.* modules.
  * @namespace Blockly.zelos
  */
-import * as goog from '../../../closure/goog/goog.js';
+import * as goog from '../../../closure/goog/goog';
 goog.declareModuleId('Blockly.zelos');
 
-import {ConstantProvider} from './constants.js';
-import {Drawer} from './drawer.js';
-import {RenderInfo} from './info.js';
-import {MarkerSvg} from './marker_svg.js';
-import {BottomRow} from './measurables/bottom_row.js';
-import {StatementInput} from './measurables/inputs.js';
-import {RightConnectionShape} from './measurables/row_elements.js';
-import {TopRow} from './measurables/top_row.js';
-import {PathObject} from './path_object.js';
-import {Renderer} from './renderer.js';
+import {ConstantProvider} from './constants';
+import {Drawer} from './drawer';
+import {RenderInfo} from './info';
+import {MarkerSvg} from './marker_svg';
+import {BottomRow} from './measurables/bottom_row';
+import {StatementInput} from './measurables/inputs';
+import {RightConnectionShape} from './measurables/row_elements';
+import {TopRow} from './measurables/top_row';
+import {PathObject} from './path_object';
+import {Renderer} from './renderer';
 
 
 export {
diff --git a/core/scrollbar.ts b/core/scrollbar.ts
index c49688ccc..c71cc801d 100644
--- a/core/scrollbar.ts
+++ b/core/scrollbar.ts
@@ -12,19 +12,19 @@
  * Object representing a scrollbar.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Scrollbar');
 
-import * as browserEvents from './browser_events.js';
-import * as Touch from './touch.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
+import * as browserEvents from './browser_events';
+import * as Touch from './touch';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
 /* eslint-disable-next-line no-unused-vars */
-import {Metrics} from './utils/metrics.js';
-import {Svg} from './utils/svg.js';
-import * as svgMath from './utils/svg_math.js';
+import {Metrics} from './utils/metrics';
+import {Svg} from './utils/svg';
+import * as svgMath from './utils/svg_math';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/scrollbar_pair.ts b/core/scrollbar_pair.ts
index 883846d3f..b061a81df 100644
--- a/core/scrollbar_pair.ts
+++ b/core/scrollbar_pair.ts
@@ -12,17 +12,17 @@
  * Object representing a pair of scrollbars.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ScrollbarPair');
 
-import * as eventUtils from './events/utils.js';
-import {Scrollbar} from './scrollbar.js';
-import * as dom from './utils/dom.js';
+import * as eventUtils from './events/utils';
+import {Scrollbar} from './scrollbar';
+import * as dom from './utils/dom';
 /* eslint-disable-next-line no-unused-vars */
-import {Metrics} from './utils/metrics.js';
-import {Svg} from './utils/svg.js';
+import {Metrics} from './utils/metrics';
+import {Svg} from './utils/svg';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/serialization/blocks.ts b/core/serialization/blocks.ts
index 28cd57cf4..00aad2c20 100644
--- a/core/serialization/blocks.ts
+++ b/core/serialization/blocks.ts
@@ -13,27 +13,27 @@
  * Handles serializing blocks to plain JavaScript objects only containing state.
  * @namespace Blockly.serialization.blocks
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.serialization.blocks');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
+import {Block} from '../block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from '../block_svg.js';
+import {BlockSvg} from '../block_svg';
 // eslint-disable-next-line no-unused-vars
-import {Connection} from '../connection.js';
-import * as eventUtils from '../events/utils.js';
-import {inputTypes} from '../input_types.js';
+import {Connection} from '../connection';
+import * as eventUtils from '../events/utils';
+import {inputTypes} from '../input_types';
 // eslint-disable-next-line no-unused-vars
-import {ISerializer} from '../interfaces/i_serializer.js';
-import {Size} from '../utils/size.js';
+import {ISerializer} from '../interfaces/i_serializer';
+import {Size} from '../utils/size';
 // eslint-disable-next-line no-unused-vars
-import {Workspace} from '../workspace.js';
-import * as Xml from '../xml.js';
+import {Workspace} from '../workspace';
+import * as Xml from '../xml';
 
-import {BadConnectionCheck, MissingBlockType, MissingConnection, RealChildOfShadow} from './exceptions.js';
-import * as priorities from './priorities.js';
-import * as serializationRegistry from './registry.js';
+import {BadConnectionCheck, MissingBlockType, MissingConnection, RealChildOfShadow} from './exceptions';
+import * as priorities from './priorities';
+import * as serializationRegistry from './registry';
 
 
 // TODO(#5160): Remove this once lint is fixed.
diff --git a/core/serialization/exceptions.ts b/core/serialization/exceptions.ts
index cadd0372f..6cc7333d7 100644
--- a/core/serialization/exceptions.ts
+++ b/core/serialization/exceptions.ts
@@ -12,14 +12,14 @@
  * Contains custom errors thrown by the serialization system.
  * @namespace Blockly.serialization.exceptions
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.serialization.exceptions');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from '../block.js';
+import {Block} from '../block';
 
 // eslint-disable-next-line no-unused-vars
-import {State} from './blocks.js';
+import {State} from './blocks';
 
 
 /** @alias Blockly.serialization.exceptions.DeserializationError */
diff --git a/core/serialization/priorities.ts b/core/serialization/priorities.ts
index 8aa79d977..68a66813a 100644
--- a/core/serialization/priorities.ts
+++ b/core/serialization/priorities.ts
@@ -16,7 +16,7 @@
  * priorities are deserialized first.
  * @namespace Blockly.serialization.priorities
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.serialization.priorities');
 
 
diff --git a/core/serialization/registry.ts b/core/serialization/registry.ts
index 3572f854d..61dc3b0dc 100644
--- a/core/serialization/registry.ts
+++ b/core/serialization/registry.ts
@@ -14,12 +14,12 @@
  * etc).
  * @namespace Blockly.serialization.registry
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.serialization.registry');
 
 // eslint-disable-next-line no-unused-vars
-import {ISerializer} from '../interfaces/i_serializer.js';
-import * as registry from '../registry.js';
+import {ISerializer} from '../interfaces/i_serializer';
+import * as registry from '../registry';
 
 
 /**
diff --git a/core/serialization/variables.ts b/core/serialization/variables.ts
index 6b329bc21..48799902d 100644
--- a/core/serialization/variables.ts
+++ b/core/serialization/variables.ts
@@ -14,16 +14,16 @@
  * state.
  * @namespace Blockly.serialization.variables
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.serialization.variables');
 
 // eslint-disable-next-line no-unused-vars
-import {ISerializer} from '../interfaces/i_serializer.js';
+import {ISerializer} from '../interfaces/i_serializer';
 // eslint-disable-next-line no-unused-vars
-import {Workspace} from '../workspace.js';
+import {Workspace} from '../workspace';
 
-import * as priorities from './priorities.js';
-import * as serializationRegistry from './registry.js';
+import * as priorities from './priorities';
+import * as serializationRegistry from './registry';
 
 
 /**
diff --git a/core/serialization/workspaces.ts b/core/serialization/workspaces.ts
index 9dc6b4b56..12dc688cc 100644
--- a/core/serialization/workspaces.ts
+++ b/core/serialization/workspaces.ts
@@ -14,16 +14,16 @@
  * objects.
  * @namespace Blockly.serialization.workspaces
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.serialization.workspaces');
 
-import * as eventUtils from '../events/utils.js';
-import {ISerializer} from '../interfaces/i_serializer.js';
-import * as registry from '../registry.js';
-import * as dom from '../utils/dom.js';
+import * as eventUtils from '../events/utils';
+import {ISerializer} from '../interfaces/i_serializer';
+import * as registry from '../registry';
+import * as dom from '../utils/dom';
 // eslint-disable-next-line no-unused-vars
-import {Workspace} from '../workspace.js';
-import {WorkspaceSvg} from '../workspace_svg.js';
+import {Workspace} from '../workspace';
+import {WorkspaceSvg} from '../workspace_svg';
 
 
 /**
diff --git a/core/shortcut_items.ts b/core/shortcut_items.ts
index c01875720..ff07fcaaf 100644
--- a/core/shortcut_items.ts
+++ b/core/shortcut_items.ts
@@ -12,18 +12,18 @@
  * Registers default keyboard shortcuts.
  * @namespace Blockly.ShortcutItems
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ShortcutItems');
 
-import {BlockSvg} from './block_svg.js';
-import * as clipboard from './clipboard.js';
-import * as common from './common.js';
-import {Gesture} from './gesture.js';
+import {BlockSvg} from './block_svg';
+import * as clipboard from './clipboard';
+import * as common from './common';
+import {Gesture} from './gesture';
 /* eslint-disable-next-line no-unused-vars */
-import {ICopyable} from './interfaces/i_copyable.js';
-import {KeyboardShortcut, ShortcutRegistry} from './shortcut_registry.js';
-import {KeyCodes} from './utils/keycodes.js';
-import {WorkspaceSvg} from './workspace_svg.js';
+import {ICopyable} from './interfaces/i_copyable';
+import {KeyboardShortcut, ShortcutRegistry} from './shortcut_registry';
+import {KeyCodes} from './utils/keycodes';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/shortcut_registry.ts b/core/shortcut_registry.ts
index 5091f6c72..75c811164 100644
--- a/core/shortcut_registry.ts
+++ b/core/shortcut_registry.ts
@@ -14,13 +14,13 @@
  * key codes used to execute those shortcuts.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ShortcutRegistry');
 
-import {KeyCodes} from './utils/keycodes.js';
-import * as object from './utils/object.js';
+import {KeyCodes} from './utils/keycodes';
+import * as object from './utils/object';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 
 
 /**
diff --git a/core/sprites.ts b/core/sprites.ts
index 13e256121..8f8150745 100644
--- a/core/sprites.ts
+++ b/core/sprites.ts
@@ -8,7 +8,7 @@
  * @fileoverview Holds constants that have to do with the sprites that create
  * the trashcan and zoom controls.
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.sprite');
 
 
diff --git a/core/theme.ts b/core/theme.ts
index d8355e054..34778ec1b 100644
--- a/core/theme.ts
+++ b/core/theme.ts
@@ -12,11 +12,11 @@
  * The class representing a theme.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Theme');
 
-import * as registry from './registry.js';
-import * as object from './utils/object.js';
+import * as registry from './registry';
+import * as object from './utils/object';
 
 
 /**
diff --git a/core/theme/classic.ts b/core/theme/classic.ts
index 2d5475faf..e20bfe72a 100644
--- a/core/theme/classic.ts
+++ b/core/theme/classic.ts
@@ -14,10 +14,10 @@
  * Contains multi-coloured border to create shadow effect.
  * @namespace Blockly.Themes.Classic
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Themes.Classic');
 
-import {Theme} from '../theme.js';
+import {Theme} from '../theme';
 
 
 const defaultBlockStyles = {
diff --git a/core/theme/themes.ts b/core/theme/themes.ts
index ebc813ac4..19f397ea5 100644
--- a/core/theme/themes.ts
+++ b/core/theme/themes.ts
@@ -12,11 +12,11 @@
  * Namespace for themes.
  * @namespace Blockly.Themes
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Themes');
 
-import {Classic} from './classic.js';
-import {Zelos} from './zelos.js';
+import {Classic} from './classic';
+import {Zelos} from './zelos';
 
 
 export {Classic, Zelos};
diff --git a/core/theme/zelos.ts b/core/theme/zelos.ts
index bb415c063..e297d0e77 100644
--- a/core/theme/zelos.ts
+++ b/core/theme/zelos.ts
@@ -12,10 +12,10 @@
  * Zelos theme.
  * @namespace Blockly.Themes.Zelos
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Themes.Zelos');
 
-import {Theme} from '../theme.js';
+import {Theme} from '../theme';
 
 
 const defaultBlockStyles = {
diff --git a/core/theme_manager.ts b/core/theme_manager.ts
index 2d3aa8caa..cf3f5a1b1 100644
--- a/core/theme_manager.ts
+++ b/core/theme_manager.ts
@@ -14,17 +14,17 @@
  *     and UI components.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ThemeManager');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Theme} from './theme.js';
-import * as arrayUtils from './utils/array.js';
-import * as dom from './utils/dom.js';
+import {Theme} from './theme';
+import * as arrayUtils from './utils/array';
+import * as dom from './utils/dom';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/toolbox/category.ts b/core/toolbox/category.ts
index df326d0df..87eb1b630 100644
--- a/core/toolbox/category.ts
+++ b/core/toolbox/category.ts
@@ -12,25 +12,25 @@
  * A toolbox category used to organize blocks in the toolbox.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.ToolboxCategory');
 
-import * as Css from '../css.js';
+import * as Css from '../css';
 /* eslint-disable-next-line no-unused-vars */
-import {ICollapsibleToolboxItem} from '../interfaces/i_collapsible_toolbox_item.js';
+import {ICollapsibleToolboxItem} from '../interfaces/i_collapsible_toolbox_item';
 /* eslint-disable-next-line no-unused-vars */
-import {ISelectableToolboxItem} from '../interfaces/i_selectable_toolbox_item.js';
+import {ISelectableToolboxItem} from '../interfaces/i_selectable_toolbox_item';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolbox} from '../interfaces/i_toolbox.js';
-import {IToolboxItem} from '../interfaces/i_toolbox_item.js';
-import * as registry from '../registry.js';
-import * as aria from '../utils/aria.js';
-import * as colourUtils from '../utils/colour.js';
-import * as dom from '../utils/dom.js';
-import * as parsing from '../utils/parsing.js';
-import * as toolbox from '../utils/toolbox.js';
+import {IToolbox} from '../interfaces/i_toolbox';
+import {IToolboxItem} from '../interfaces/i_toolbox_item';
+import * as registry from '../registry';
+import * as aria from '../utils/aria';
+import * as colourUtils from '../utils/colour';
+import * as dom from '../utils/dom';
+import * as parsing from '../utils/parsing';
+import * as toolbox from '../utils/toolbox';
 
-import {ToolboxItem} from './toolbox_item.js';
+import {ToolboxItem} from './toolbox_item';
 
 
 /**
diff --git a/core/toolbox/collapsible_category.ts b/core/toolbox/collapsible_category.ts
index 62d46f87a..2dbd46b0a 100644
--- a/core/toolbox/collapsible_category.ts
+++ b/core/toolbox/collapsible_category.ts
@@ -12,22 +12,22 @@
  * A toolbox category used to organize blocks in the toolbox.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.CollapsibleToolboxCategory');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ICollapsibleToolboxItem} from '../interfaces/i_collapsible_toolbox_item.js';
+import {ICollapsibleToolboxItem} from '../interfaces/i_collapsible_toolbox_item';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolbox} from '../interfaces/i_toolbox.js';
+import {IToolbox} from '../interfaces/i_toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolboxItem} from '../interfaces/i_toolbox_item.js';
-import * as registry from '../registry.js';
-import * as aria from '../utils/aria.js';
-import * as dom from '../utils/dom.js';
-import * as toolbox from '../utils/toolbox.js';
+import {IToolboxItem} from '../interfaces/i_toolbox_item';
+import * as registry from '../registry';
+import * as aria from '../utils/aria';
+import * as dom from '../utils/dom';
+import * as toolbox from '../utils/toolbox';
 
-import {ToolboxCategory} from './category.js';
-import {ToolboxSeparator} from './separator.js';
+import {ToolboxCategory} from './category';
+import {ToolboxSeparator} from './separator';
 
 
 /**
diff --git a/core/toolbox/separator.ts b/core/toolbox/separator.ts
index 43b2a1fb5..17ccefce8 100644
--- a/core/toolbox/separator.ts
+++ b/core/toolbox/separator.ts
@@ -12,18 +12,18 @@
  * A separator used for separating toolbox categories.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.ToolboxSeparator');
 
-import * as Css from '../css.js';
+import * as Css from '../css';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolbox} from '../interfaces/i_toolbox.js';
-import * as registry from '../registry.js';
-import * as dom from '../utils/dom.js';
+import {IToolbox} from '../interfaces/i_toolbox';
+import * as registry from '../registry';
+import * as dom from '../utils/dom';
 /* eslint-disable-next-line no-unused-vars */
-import * as toolbox from '../utils/toolbox.js';
+import * as toolbox from '../utils/toolbox';
 
-import {ToolboxItem} from './toolbox_item.js';
+import {ToolboxItem} from './toolbox_item';
 
 
 /**
diff --git a/core/toolbox/toolbox.ts b/core/toolbox/toolbox.ts
index c6d4d60ae..d863385b4 100644
--- a/core/toolbox/toolbox.ts
+++ b/core/toolbox/toolbox.ts
@@ -12,57 +12,57 @@
  * Toolbox from whence to create blocks.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.Toolbox');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../shortcut_registry.js';
+import '../shortcut_registry';
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../events/events_toolbox_item_select.js';
+import '../events/events_toolbox_item_select';
 
-import {BlockSvg} from '../block_svg.js';
+import {BlockSvg} from '../block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {BlocklyOptions} from '../blockly_options.js';
-import * as browserEvents from '../browser_events.js';
-import * as common from '../common.js';
-import {ComponentManager} from '../component_manager.js';
-import * as Css from '../css.js';
-import {DeleteArea} from '../delete_area.js';
-import * as eventUtils from '../events/utils.js';
+import {BlocklyOptions} from '../blockly_options';
+import * as browserEvents from '../browser_events';
+import * as common from '../common';
+import {ComponentManager} from '../component_manager';
+import * as Css from '../css';
+import {DeleteArea} from '../delete_area';
+import * as eventUtils from '../events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {IAutoHideable} from '../interfaces/i_autohideable.js';
+import {IAutoHideable} from '../interfaces/i_autohideable';
 /* eslint-disable-next-line no-unused-vars */
-import {ICollapsibleToolboxItem} from '../interfaces/i_collapsible_toolbox_item.js';
+import {ICollapsibleToolboxItem} from '../interfaces/i_collapsible_toolbox_item';
 /* eslint-disable-next-line no-unused-vars */
-import {IDraggable} from '../interfaces/i_draggable.js';
+import {IDraggable} from '../interfaces/i_draggable';
 /* eslint-disable-next-line no-unused-vars */
-import {IFlyout} from '../interfaces/i_flyout.js';
+import {IFlyout} from '../interfaces/i_flyout';
 /* eslint-disable-next-line no-unused-vars */
-import {IKeyboardAccessible} from '../interfaces/i_keyboard_accessible.js';
+import {IKeyboardAccessible} from '../interfaces/i_keyboard_accessible';
 /* eslint-disable-next-line no-unused-vars */
-import {ISelectableToolboxItem} from '../interfaces/i_selectable_toolbox_item.js';
+import {ISelectableToolboxItem} from '../interfaces/i_selectable_toolbox_item';
 /* eslint-disable-next-line no-unused-vars */
-import {IStyleable} from '../interfaces/i_styleable.js';
+import {IStyleable} from '../interfaces/i_styleable';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolbox} from '../interfaces/i_toolbox.js';
+import {IToolbox} from '../interfaces/i_toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolboxItem} from '../interfaces/i_toolbox_item.js';
-import {Options} from '../options.js';
-import * as registry from '../registry.js';
-import {KeyboardShortcut} from '../shortcut_registry.js';
-import * as Touch from '../touch.js';
-import * as aria from '../utils/aria.js';
-import * as dom from '../utils/dom.js';
-import {KeyCodes} from '../utils/keycodes.js';
-import {Rect} from '../utils/rect.js';
-import * as toolbox from '../utils/toolbox.js';
+import {IToolboxItem} from '../interfaces/i_toolbox_item';
+import {Options} from '../options';
+import * as registry from '../registry';
+import {KeyboardShortcut} from '../shortcut_registry';
+import * as Touch from '../touch';
+import * as aria from '../utils/aria';
+import * as dom from '../utils/dom';
+import {KeyCodes} from '../utils/keycodes';
+import {Rect} from '../utils/rect';
+import * as toolbox from '../utils/toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../workspace_svg.js';
+import {WorkspaceSvg} from '../workspace_svg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ToolboxCategory} from './category.js';
-import {CollapsibleToolboxCategory} from './collapsible_category.js';
+import {ToolboxCategory} from './category';
+import {CollapsibleToolboxCategory} from './collapsible_category';
 
 
 /**
diff --git a/core/toolbox/toolbox_item.ts b/core/toolbox/toolbox_item.ts
index f06cb79ac..929ee8b42 100644
--- a/core/toolbox/toolbox_item.ts
+++ b/core/toolbox/toolbox_item.ts
@@ -12,20 +12,20 @@
  * An item in the toolbox.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.ToolboxItem');
 
 /* eslint-disable-next-line no-unused-vars */
-import {ICollapsibleToolboxItem} from '../interfaces/i_collapsible_toolbox_item.js';
+import {ICollapsibleToolboxItem} from '../interfaces/i_collapsible_toolbox_item';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolbox} from '../interfaces/i_toolbox.js';
+import {IToolbox} from '../interfaces/i_toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolboxItem} from '../interfaces/i_toolbox_item.js';
-import * as idGenerator from '../utils/idgenerator.js';
+import {IToolboxItem} from '../interfaces/i_toolbox_item';
+import * as idGenerator from '../utils/idgenerator';
 /* eslint-disable-next-line no-unused-vars */
-import * as toolbox from '../utils/toolbox.js';
+import * as toolbox from '../utils/toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../workspace_svg.js';
+import {WorkspaceSvg} from '../workspace_svg';
 
 
 /**
diff --git a/core/tooltip.ts b/core/tooltip.ts
index 915e545d7..0e8ca61c6 100644
--- a/core/tooltip.ts
+++ b/core/tooltip.ts
@@ -13,12 +13,12 @@
  * tooltip will be used. Third, call bindMouseEvents(e) passing the SVG element.
  * @namespace Blockly.Tooltip
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Tooltip');
 
-import * as browserEvents from './browser_events.js';
-import * as common from './common.js';
-import * as blocklyString from './utils/string.js';
+import * as browserEvents from './browser_events';
+import * as common from './common';
+import * as blocklyString from './utils/string';
 
 
 /**
diff --git a/core/touch.ts b/core/touch.ts
index 2211a6903..39256ab6f 100644
--- a/core/touch.ts
+++ b/core/touch.ts
@@ -12,11 +12,11 @@
  * Touch handling for Blockly.
  * @namespace Blockly.Touch
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Touch');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Gesture} from './gesture.js';
+import {Gesture} from './gesture';
 
 
 /**
diff --git a/core/touch_gesture.ts b/core/touch_gesture.ts
index fa038e11f..8305ec795 100644
--- a/core/touch_gesture.ts
+++ b/core/touch_gesture.ts
@@ -14,15 +14,15 @@
  * for both pointer and touch events.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.TouchGesture');
 
-import * as browserEvents from './browser_events.js';
-import {Gesture} from './gesture.js';
-import * as Touch from './touch.js';
-import {Coordinate} from './utils/coordinate.js';
+import * as browserEvents from './browser_events';
+import {Gesture} from './gesture';
+import * as Touch from './touch';
+import {Coordinate} from './utils/coordinate';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /*
diff --git a/core/trashcan.ts b/core/trashcan.ts
index 726782146..5b2bb9619 100644
--- a/core/trashcan.ts
+++ b/core/trashcan.ts
@@ -12,47 +12,47 @@
  * Object representing a trash can icon.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Trashcan');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './metrics_manager.js';
+import './metrics_manager';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_trashcan_open.js';
+import './events/events_trashcan_open';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlocklyOptions} from './blockly_options.js';
-import * as browserEvents from './browser_events.js';
-import {ComponentManager} from './component_manager.js';
-import {DeleteArea} from './delete_area.js';
+import {BlocklyOptions} from './blockly_options';
+import * as browserEvents from './browser_events';
+import {ComponentManager} from './component_manager';
+import {DeleteArea} from './delete_area';
 /* eslint-disable-next-line no-unused-vars */
-import {Abstract} from './events/events_abstract.js';
+import {Abstract} from './events/events_abstract';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockDelete} from './events/events_block_delete.js';
-import * as eventUtils from './events/utils.js';
+import {BlockDelete} from './events/events_block_delete';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {IAutoHideable} from './interfaces/i_autohideable.js';
+import {IAutoHideable} from './interfaces/i_autohideable';
 /* eslint-disable-next-line no-unused-vars */
-import {IDraggable} from './interfaces/i_draggable.js';
+import {IDraggable} from './interfaces/i_draggable';
 /* eslint-disable-next-line no-unused-vars */
-import {IFlyout} from './interfaces/i_flyout.js';
+import {IFlyout} from './interfaces/i_flyout';
 /* eslint-disable-next-line no-unused-vars */
-import {IPositionable} from './interfaces/i_positionable.js';
-import {UiMetrics} from './metrics_manager.js';
-import {Options} from './options.js';
-import * as uiPosition from './positionable_helpers.js';
-import * as registry from './registry.js';
+import {IPositionable} from './interfaces/i_positionable';
+import {UiMetrics} from './metrics_manager';
+import {Options} from './options';
+import * as uiPosition from './positionable_helpers';
+import * as registry from './registry';
 /* eslint-disable-next-line no-unused-vars */
-import * as blocks from './serialization/blocks.js';
-import {SPRITE} from './sprites.js';
-import * as dom from './utils/dom.js';
-import {Rect} from './utils/rect.js';
-import {Size} from './utils/size.js';
-import {Svg} from './utils/svg.js';
-import * as toolbox from './utils/toolbox.js';
+import * as blocks from './serialization/blocks';
+import {SPRITE} from './sprites';
+import * as dom from './utils/dom';
+import {Rect} from './utils/rect';
+import {Size} from './utils/size';
+import {Svg} from './utils/svg';
+import * as toolbox from './utils/toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/utils.ts b/core/utils.ts
index ee9c97178..f90a6d845 100644
--- a/core/utils.ts
+++ b/core/utils.ts
@@ -12,38 +12,38 @@
  * Utility methods.
  * @namespace Blockly.utils
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.utils');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
-import * as browserEvents from './browser_events.js';
-import * as common from './common.js';
-import * as extensions from './extensions.js';
-import * as aria from './utils/aria.js';
-import * as arrayUtils from './utils/array.js';
-import * as colour from './utils/colour.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as deprecation from './utils/deprecation.js';
-import * as dom from './utils/dom.js';
-import * as idGenerator from './utils/idgenerator.js';
-import {KeyCodes} from './utils/keycodes.js';
-import * as math from './utils/math.js';
-import {Metrics} from './utils/metrics.js';
-import * as object from './utils/object.js';
-import * as parsing from './utils/parsing.js';
-import {Rect} from './utils/rect.js';
-import {Size} from './utils/size.js';
-import * as stringUtils from './utils/string.js';
-import * as style from './utils/style.js';
-import {Svg} from './utils/svg.js';
-import * as svgMath from './utils/svg_math.js';
-import * as svgPaths from './utils/svg_paths.js';
-import * as toolbox from './utils/toolbox.js';
-import * as userAgent from './utils/useragent.js';
-import * as xml from './utils/xml.js';
+import {Block} from './block';
+import * as browserEvents from './browser_events';
+import * as common from './common';
+import * as extensions from './extensions';
+import * as aria from './utils/aria';
+import * as arrayUtils from './utils/array';
+import * as colour from './utils/colour';
+import {Coordinate} from './utils/coordinate';
+import * as deprecation from './utils/deprecation';
+import * as dom from './utils/dom';
+import * as idGenerator from './utils/idgenerator';
+import {KeyCodes} from './utils/keycodes';
+import * as math from './utils/math';
+import {Metrics} from './utils/metrics';
+import * as object from './utils/object';
+import * as parsing from './utils/parsing';
+import {Rect} from './utils/rect';
+import {Size} from './utils/size';
+import * as stringUtils from './utils/string';
+import * as style from './utils/style';
+import {Svg} from './utils/svg';
+import * as svgMath from './utils/svg_math';
+import * as svgPaths from './utils/svg_paths';
+import * as toolbox from './utils/toolbox';
+import * as userAgent from './utils/useragent';
+import * as xml from './utils/xml';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 export {
diff --git a/core/utils/aria.ts b/core/utils/aria.ts
index daef600b6..abd597ddc 100644
--- a/core/utils/aria.ts
+++ b/core/utils/aria.ts
@@ -16,7 +16,7 @@
  * a JavaScript framework such as Closure.
  * @namespace Blockly.utils.aria
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.aria');
 
 
diff --git a/core/utils/array.ts b/core/utils/array.ts
index 12a0cadda..58a78d79c 100644
--- a/core/utils/array.ts
+++ b/core/utils/array.ts
@@ -9,7 +9,7 @@
  */
 
 /** @namespace Blockly.utils.array */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.array');
 
 
diff --git a/core/utils/colour.ts b/core/utils/colour.ts
index a669bce65..10b04f8f7 100644
--- a/core/utils/colour.ts
+++ b/core/utils/colour.ts
@@ -12,7 +12,7 @@
  * Utility methods for colour manipulation.
  * @namespace Blockly.utils.colour
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.colour');
 
 
diff --git a/core/utils/coordinate.ts b/core/utils/coordinate.ts
index 58390cdbf..79a9cc0d8 100644
--- a/core/utils/coordinate.ts
+++ b/core/utils/coordinate.ts
@@ -16,7 +16,7 @@
  * a JavaScript framework such as Closure.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.Coordinate');
 
 
diff --git a/core/utils/deprecation.ts b/core/utils/deprecation.ts
index d4917e667..6f86dd54c 100644
--- a/core/utils/deprecation.ts
+++ b/core/utils/deprecation.ts
@@ -14,7 +14,7 @@
  * This method is not specific to Blockly.
  * @namespace Blockly.utils.deprecation
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.deprecation');
 
 
diff --git a/core/utils/dom.ts b/core/utils/dom.ts
index 4acd6a800..28d404be4 100644
--- a/core/utils/dom.ts
+++ b/core/utils/dom.ts
@@ -16,12 +16,12 @@
  * a JavaScript framework such as Closure.
  * @namespace Blockly.utils.dom
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.dom');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Svg} from './svg.js';
-import * as userAgent from './useragent.js';
+import {Svg} from './svg';
+import * as userAgent from './useragent';
 
 
 /**
diff --git a/core/utils/idgenerator.ts b/core/utils/idgenerator.ts
index d292deec3..f24c098df 100644
--- a/core/utils/idgenerator.ts
+++ b/core/utils/idgenerator.ts
@@ -12,7 +12,7 @@
  * Generators for unique IDs.
  * @namespace Blockly.utils.idGenerator
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.idGenerator');
 
 
diff --git a/core/utils/keycodes.ts b/core/utils/keycodes.ts
index 06d8c7b61..b2097eab5 100644
--- a/core/utils/keycodes.ts
+++ b/core/utils/keycodes.ts
@@ -16,7 +16,7 @@
  * a JavaScript framework such as Closure.
  * @namespace Blockly.utils.KeyCodes
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.KeyCodes');
 
 
diff --git a/core/utils/math.ts b/core/utils/math.ts
index c930b2627..a81054642 100644
--- a/core/utils/math.ts
+++ b/core/utils/math.ts
@@ -16,7 +16,7 @@
  * a JavaScript framework such as Closure.
  * @namespace Blockly.utils.math
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.math');
 
 
diff --git a/core/utils/metrics.ts b/core/utils/metrics.ts
index 2ec83b7e0..84aef136e 100644
--- a/core/utils/metrics.ts
+++ b/core/utils/metrics.ts
@@ -12,7 +12,7 @@
  * Workspace metrics definitions.
  * @namespace Blockly.utils.Metrics
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.Metrics');
 
 
diff --git a/core/utils/object.ts b/core/utils/object.ts
index 364759f03..01b20fb12 100644
--- a/core/utils/object.ts
+++ b/core/utils/object.ts
@@ -12,10 +12,10 @@
  * Utility methods for objects.
  * @namespace Blockly.utils.object
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.object');
 
-import * as deprecation from './deprecation.js';
+import * as deprecation from './deprecation';
 
 
 /**
diff --git a/core/utils/parsing.ts b/core/utils/parsing.ts
index 3b9e616d5..f1375811f 100644
--- a/core/utils/parsing.ts
+++ b/core/utils/parsing.ts
@@ -11,12 +11,12 @@
 /**
  * @namespace Blockly.utils.parsing
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.parsing');
 
-import {Msg} from '../msg.js';
+import {Msg} from '../msg';
 
-import * as colourUtils from './colour.js';
+import * as colourUtils from './colour';
 
 
 /**
diff --git a/core/utils/rect.ts b/core/utils/rect.ts
index 9364bcc66..52e340e2e 100644
--- a/core/utils/rect.ts
+++ b/core/utils/rect.ts
@@ -16,7 +16,7 @@
  * a JavaScript framework such as Closure.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.Rect');
 
 
diff --git a/core/utils/sentinel.ts b/core/utils/sentinel.ts
index ab1636a81..e978f2279 100644
--- a/core/utils/sentinel.ts
+++ b/core/utils/sentinel.ts
@@ -12,7 +12,7 @@
  * A type used to create flag values.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.Sentinel');
 
 
diff --git a/core/utils/size.ts b/core/utils/size.ts
index d2a236e0d..0eea2c235 100644
--- a/core/utils/size.ts
+++ b/core/utils/size.ts
@@ -16,7 +16,7 @@
  * a JavaScript framework such as Closure.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.Size');
 
 
diff --git a/core/utils/string.ts b/core/utils/string.ts
index 2d919ce24..474b10ac2 100644
--- a/core/utils/string.ts
+++ b/core/utils/string.ts
@@ -16,10 +16,10 @@
  * a JavaScript framework such as Closure.
  * @namespace Blockly.utils.string
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.string');
 
-import * as deprecation from './deprecation.js';
+import * as deprecation from './deprecation';
 
 
 /**
diff --git a/core/utils/style.ts b/core/utils/style.ts
index 4ef2f26ef..67207059b 100644
--- a/core/utils/style.ts
+++ b/core/utils/style.ts
@@ -16,12 +16,12 @@
  * a JavaScript framework such as Closure.
  * @namespace Blockly.utils.style
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.style');
 
-import {Coordinate} from './coordinate.js';
-import {Rect} from './rect.js';
-import {Size} from './size.js';
+import {Coordinate} from './coordinate';
+import {Rect} from './rect';
+import {Size} from './size';
 
 
 /**
diff --git a/core/utils/svg.ts b/core/utils/svg.ts
index aa7ae7eb6..b973ac506 100644
--- a/core/utils/svg.ts
+++ b/core/utils/svg.ts
@@ -14,7 +14,7 @@
  * all SVG tag names used by Blockly.
  * @class
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.Svg');
 
 
diff --git a/core/utils/svg_math.ts b/core/utils/svg_math.ts
index 960d48146..1e3285168 100644
--- a/core/utils/svg_math.ts
+++ b/core/utils/svg_math.ts
@@ -12,18 +12,18 @@
  * Utility methods realted to figuring out positions of SVG elements.
  * @namespace Blockly.utils.svgMath
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.svgMath');
 
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from '../workspace_svg.js';
+import {WorkspaceSvg} from '../workspace_svg';
 
-import {Coordinate} from './coordinate.js';
-import * as deprecation from './deprecation.js';
-import {Rect} from './rect.js';
-import {Size} from './size.js';
-import * as style from './style.js';
-import * as userAgent from './useragent.js';
+import {Coordinate} from './coordinate';
+import * as deprecation from './deprecation';
+import {Rect} from './rect';
+import {Size} from './size';
+import * as style from './style';
+import * as userAgent from './useragent';
 
 
 /**
diff --git a/core/utils/svg_paths.ts b/core/utils/svg_paths.ts
index c13a4d839..c8384b2ea 100644
--- a/core/utils/svg_paths.ts
+++ b/core/utils/svg_paths.ts
@@ -13,7 +13,7 @@
  * Methods for creating parts of SVG path strings.  See
  * @namespace Blockly.utils.svgPaths
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.svgPaths');
 
 
diff --git a/core/utils/toolbox.ts b/core/utils/toolbox.ts
index 1f74a3265..b51fcba50 100644
--- a/core/utils/toolbox.ts
+++ b/core/utils/toolbox.ts
@@ -12,22 +12,22 @@
  * Utility functions for the toolbox and flyout.
  * @namespace Blockly.utils.toolbox
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.toolbox');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../toolbox/category.js';
+import '../toolbox/category';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import '../toolbox/separator.js';
+import '../toolbox/separator';
 
 /* eslint-disable-next-line no-unused-vars */
-import {ConnectionState} from '../serialization/blocks.js';
-import {CssConfig as CategoryCssConfig} from '../toolbox/category.js';
-import {CssConfig as SeparatorCssConfig} from '../toolbox/separator.js';
-import * as Xml from '../xml.js';
-import * as userAgent from './useragent.js';
+import {ConnectionState} from '../serialization/blocks';
+import {CssConfig as CategoryCssConfig} from '../toolbox/category';
+import {CssConfig as SeparatorCssConfig} from '../toolbox/separator';
+import * as Xml from '../xml';
+import * as userAgent from './useragent';
 
 
 /**
diff --git a/core/utils/useragent.ts b/core/utils/useragent.ts
index 587936e9a..fa80eafce 100644
--- a/core/utils/useragent.ts
+++ b/core/utils/useragent.ts
@@ -16,7 +16,7 @@
  * a JavaScript framework such as Closure.
  * @namespace Blockly.utils.userAgent
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.userAgent');
 
 
diff --git a/core/utils/xml.ts b/core/utils/xml.ts
index 169e78086..7b5ce603e 100644
--- a/core/utils/xml.ts
+++ b/core/utils/xml.ts
@@ -16,7 +16,7 @@
  * a JavaScript framework such as Closure.
  * @namespace Blockly.utils.xml
  */
-import * as goog from '../../closure/goog/goog.js';
+import * as goog from '../../closure/goog/goog';
 goog.declareModuleId('Blockly.utils.xml');
 
 
diff --git a/core/variable_map.ts b/core/variable_map.ts
index 14d86bc6b..6c52872df 100644
--- a/core/variable_map.ts
+++ b/core/variable_map.ts
@@ -12,25 +12,25 @@
  * Object representing a map of variables and their types.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.VariableMap');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_var_delete.js';
+import './events/events_var_delete';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_var_rename.js';
+import './events/events_var_rename';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
-import * as dialog from './dialog.js';
-import * as eventUtils from './events/utils.js';
-import {Msg} from './msg.js';
-import {Names} from './names.js';
-import * as arrayUtils from './utils/array.js';
-import * as idGenerator from './utils/idgenerator.js';
-import {VariableModel} from './variable_model.js';
+import {Block} from './block';
+import * as dialog from './dialog';
+import * as eventUtils from './events/utils';
+import {Msg} from './msg';
+import {Names} from './names';
+import * as arrayUtils from './utils/array';
+import * as idGenerator from './utils/idgenerator';
+import {VariableModel} from './variable_model';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 
 
 /**
diff --git a/core/variable_model.ts b/core/variable_model.ts
index f771cb0d5..43522b701 100644
--- a/core/variable_model.ts
+++ b/core/variable_model.ts
@@ -12,16 +12,16 @@
  * Components for the variable model.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.VariableModel');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_var_create.js';
+import './events/events_var_create';
 
-import * as eventUtils from './events/utils.js';
-import * as idGenerator from './utils/idgenerator.js';
+import * as eventUtils from './events/utils';
+import * as idGenerator from './utils/idgenerator';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 
 
 /**
diff --git a/core/variables.ts b/core/variables.ts
index 07a6756cf..717fa31fb 100644
--- a/core/variables.ts
+++ b/core/variables.ts
@@ -12,19 +12,19 @@
  * Utility functions for handling variables.
  * @namespace Blockly.Variables
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Variables');
 
-import {Blocks} from './blocks.js';
-import * as dialog from './dialog.js';
-import {Msg} from './msg.js';
-import * as utilsXml from './utils/xml.js';
-import {VariableModel} from './variable_model.js';
+import {Blocks} from './blocks';
+import * as dialog from './dialog';
+import {Msg} from './msg';
+import * as utilsXml from './utils/xml';
+import {VariableModel} from './variable_model';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
-import * as Xml from './xml.js';
+import {WorkspaceSvg} from './workspace_svg';
+import * as Xml from './xml';
 
 
 /**
diff --git a/core/variables_dynamic.ts b/core/variables_dynamic.ts
index 86fa7cd44..6bc91e170 100644
--- a/core/variables_dynamic.ts
+++ b/core/variables_dynamic.ts
@@ -13,18 +13,18 @@
  *
  * @namespace Blockly.VariablesDynamic
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.VariablesDynamic');
 
-import {Blocks} from './blocks.js';
-import {Msg} from './msg.js';
-import * as xml from './utils/xml.js';
-import {VariableModel} from './variable_model.js';
-import * as Variables from './variables.js';
+import {Blocks} from './blocks';
+import {Msg} from './msg';
+import * as xml from './utils/xml';
+import {VariableModel} from './variable_model';
+import * as Variables from './variables';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/warning.ts b/core/warning.ts
index 19be46692..81c855b87 100644
--- a/core/warning.ts
+++ b/core/warning.ts
@@ -12,21 +12,21 @@
  * Object representing a warning.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Warning');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_bubble_open.js';
+import './events/events_bubble_open';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
-import {Bubble} from './bubble.js';
-import * as eventUtils from './events/utils.js';
-import {Icon} from './icon.js';
+import {BlockSvg} from './block_svg';
+import {Bubble} from './bubble';
+import * as eventUtils from './events/utils';
+import {Icon} from './icon';
 /* eslint-disable-next-line no-unused-vars */
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {Svg} from './utils/svg.js';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {Svg} from './utils/svg';
 
 
 /**
diff --git a/core/widgetdiv.ts b/core/widgetdiv.ts
index 56721a31e..07552619b 100644
--- a/core/widgetdiv.ts
+++ b/core/widgetdiv.ts
@@ -16,17 +16,17 @@
  *     E.g. text input areas, colour pickers, context menus.
  * @namespace Blockly.WidgetDiv
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.WidgetDiv');
 
-import * as common from './common.js';
-import * as dom from './utils/dom.js';
+import * as common from './common';
+import * as dom from './utils/dom';
 /* eslint-disable-next-line no-unused-vars */
-import {Rect} from './utils/rect.js';
+import {Rect} from './utils/rect';
 /* eslint-disable-next-line no-unused-vars */
-import {Size} from './utils/size.js';
+import {Size} from './utils/size';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /** The object currently using this container. */
diff --git a/core/workspace.ts b/core/workspace.ts
index b557ec1d0..638be707b 100644
--- a/core/workspace.ts
+++ b/core/workspace.ts
@@ -12,37 +12,37 @@
  * Object representing a workspace.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Workspace');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './connection_checker.js';
+import './connection_checker';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlocklyOptions} from './blockly_options.js';
+import {BlocklyOptions} from './blockly_options';
 /* eslint-disable-next-line no-unused-vars */
-import {ConnectionDB} from './connection_db.js';
+import {ConnectionDB} from './connection_db';
 /* eslint-disable-next-line no-unused-vars */
-import {Abstract} from './events/events_abstract.js';
-import * as eventUtils from './events/utils.js';
+import {Abstract} from './events/events_abstract';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocation} from './interfaces/i_ast_node_location.js';
+import {IASTNodeLocation} from './interfaces/i_ast_node_location';
 /* eslint-disable-next-line no-unused-vars */
-import {IConnectionChecker} from './interfaces/i_connection_checker.js';
-import {Options} from './options.js';
-import * as registry from './registry.js';
-import * as arrayUtils from './utils/array.js';
-import * as idGenerator from './utils/idgenerator.js';
-import * as math from './utils/math.js';
+import {IConnectionChecker} from './interfaces/i_connection_checker';
+import {Options} from './options';
+import * as registry from './registry';
+import * as arrayUtils from './utils/array';
+import * as idGenerator from './utils/idgenerator';
+import * as math from './utils/math';
 /* eslint-disable-next-line no-unused-vars */
-import * as toolbox from './utils/toolbox.js';
-import {VariableMap} from './variable_map.js';
+import * as toolbox from './utils/toolbox';
+import {VariableMap} from './variable_map';
 /* eslint-disable-next-line no-unused-vars */
-import {VariableModel} from './variable_model.js';
+import {VariableModel} from './variable_model';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceComment} from './workspace_comment.js';
+import {WorkspaceComment} from './workspace_comment';
 
 
 /** Database of all workspaces. */
diff --git a/core/workspace_audio.ts b/core/workspace_audio.ts
index a2b88a1b6..32a3854a2 100644
--- a/core/workspace_audio.ts
+++ b/core/workspace_audio.ts
@@ -14,12 +14,12 @@
  *     workspace.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.WorkspaceAudio');
 
-import * as userAgent from './utils/useragent.js';
+import * as userAgent from './utils/useragent';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/workspace_comment.ts b/core/workspace_comment.ts
index a14e6d64c..99d13f260 100644
--- a/core/workspace_comment.ts
+++ b/core/workspace_comment.ts
@@ -12,24 +12,24 @@
  * Object representing a code comment on the workspace.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.WorkspaceComment');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_comment_change.js';
+import './events/events_comment_change';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_comment_create.js';
+import './events/events_comment_create';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_comment_delete.js';
+import './events/events_comment_delete';
 
 /* eslint-disable-next-line no-unused-vars */
-import {CommentMove} from './events/events_comment_move.js';
-import * as eventUtils from './events/utils.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as idGenerator from './utils/idgenerator.js';
-import * as xml from './utils/xml.js';
+import {CommentMove} from './events/events_comment_move';
+import * as eventUtils from './events/utils';
+import {Coordinate} from './utils/coordinate';
+import * as idGenerator from './utils/idgenerator';
+import * as xml from './utils/xml';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
+import {Workspace} from './workspace';
 
 
 /**
diff --git a/core/workspace_comment_svg.ts b/core/workspace_comment_svg.ts
index 952e9fe2b..3d2a8d5aa 100644
--- a/core/workspace_comment_svg.ts
+++ b/core/workspace_comment_svg.ts
@@ -12,39 +12,39 @@
  * Object representing a code comment on a rendered workspace.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.WorkspaceCommentSvg');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_comment_create.js';
+import './events/events_comment_create';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_comment_delete.js';
+import './events/events_comment_delete';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_selected.js';
+import './events/events_selected';
 
 /* eslint-disable-next-line no-unused-vars */
-import {BlockDragSurfaceSvg} from './block_drag_surface.js';
-import * as browserEvents from './browser_events.js';
-import * as common from './common.js';
-import * as ContextMenu from './contextmenu.js';
-import * as Css from './css.js';
+import {BlockDragSurfaceSvg} from './block_drag_surface';
+import * as browserEvents from './browser_events';
+import * as common from './common';
+import * as ContextMenu from './contextmenu';
+import * as Css from './css';
 /* eslint-disable-next-line no-unused-vars */
-import {CommentMove} from './events/events_comment_move.js';
-import * as eventUtils from './events/utils.js';
+import {CommentMove} from './events/events_comment_move';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {IBoundedElement} from './interfaces/i_bounded_element.js';
+import {IBoundedElement} from './interfaces/i_bounded_element';
 /* eslint-disable-next-line no-unused-vars */
-import {IBubble} from './interfaces/i_bubble.js';
-import {CopyData, ICopyable} from './interfaces/i_copyable.js';
-import * as Touch from './touch.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {Rect} from './utils/rect.js';
-import {Svg} from './utils/svg.js';
-import * as svgMath from './utils/svg_math.js';
-import {WorkspaceComment} from './workspace_comment.js';
+import {IBubble} from './interfaces/i_bubble';
+import {CopyData, ICopyable} from './interfaces/i_copyable';
+import * as Touch from './touch';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {Rect} from './utils/rect';
+import {Svg} from './utils/svg';
+import * as svgMath from './utils/svg_math';
+import {WorkspaceComment} from './workspace_comment';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /** Size of the resize icon. */
diff --git a/core/workspace_drag_surface_svg.ts b/core/workspace_drag_surface_svg.ts
index 1087298fc..e6a07554c 100644
--- a/core/workspace_drag_surface_svg.ts
+++ b/core/workspace_drag_surface_svg.ts
@@ -18,14 +18,14 @@
  * blocks are never repainted during drag improving performance.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.WorkspaceDragSurfaceSvg');
 
 /* eslint-disable-next-line no-unused-vars */
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
-import {Svg} from './utils/svg.js';
-import * as svgMath from './utils/svg_math.js';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
+import {Svg} from './utils/svg';
+import * as svgMath from './utils/svg_math';
 
 
 /**
diff --git a/core/workspace_dragger.ts b/core/workspace_dragger.ts
index abdfbb6f6..96ea613f9 100644
--- a/core/workspace_dragger.ts
+++ b/core/workspace_dragger.ts
@@ -12,13 +12,13 @@
  * Methods for dragging a workspace visually.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.WorkspaceDragger');
 
-import * as common from './common.js';
-import {Coordinate} from './utils/coordinate.js';
+import * as common from './common';
+import {Coordinate} from './utils/coordinate';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/workspace_svg.ts b/core/workspace_svg.ts
index bacb17210..6e745cbb1 100644
--- a/core/workspace_svg.ts
+++ b/core/workspace_svg.ts
@@ -12,118 +12,118 @@
  * Object representing a workspace rendered as SVG.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.WorkspaceSvg');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './procedures.js';
+import './procedures';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './variables.js';
+import './variables';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './variables_dynamic.js';
+import './variables_dynamic';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './rendered_connection.js';
+import './rendered_connection';
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './zoom_controls.js';
+import './zoom_controls';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_block_create.js';
+import './events/events_block_create';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_theme_change.js';
+import './events/events_theme_change';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_viewport.js';
+import './events/events_viewport';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './metrics_manager.js';
+import './metrics_manager';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './msg.js';
+import './msg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockDragSurfaceSvg} from './block_drag_surface.js';
-import {BlockSvg} from './block_svg.js';
+import {BlockDragSurfaceSvg} from './block_drag_surface';
+import {BlockSvg} from './block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {BlocklyOptions} from './blockly_options.js';
-import * as browserEvents from './browser_events.js';
-import * as common from './common.js';
-import {ComponentManager} from './component_manager.js';
-import {config} from './config.js';
-import {ConnectionDB} from './connection_db.js';
-import * as ContextMenu from './contextmenu.js';
-import {ContextMenuRegistry} from './contextmenu_registry.js';
-import * as dropDownDiv from './dropdowndiv.js';
-import * as eventUtils from './events/utils.js';
+import {BlocklyOptions} from './blockly_options';
+import * as browserEvents from './browser_events';
+import * as common from './common';
+import {ComponentManager} from './component_manager';
+import {config} from './config';
+import {ConnectionDB} from './connection_db';
+import * as ContextMenu from './contextmenu';
+import {ContextMenuRegistry} from './contextmenu_registry';
+import * as dropDownDiv from './dropdowndiv';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {FlyoutButton} from './flyout_button.js';
-import {Gesture} from './gesture.js';
-import {Grid} from './grid.js';
+import {FlyoutButton} from './flyout_button';
+import {Gesture} from './gesture';
+import {Grid} from './grid';
 /* eslint-disable-next-line no-unused-vars */
-import {IASTNodeLocationSvg} from './interfaces/i_ast_node_location_svg.js';
+import {IASTNodeLocationSvg} from './interfaces/i_ast_node_location_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {IBoundedElement} from './interfaces/i_bounded_element.js';
+import {IBoundedElement} from './interfaces/i_bounded_element';
 /* eslint-disable-next-line no-unused-vars */
-import {ICopyable} from './interfaces/i_copyable.js';
+import {ICopyable} from './interfaces/i_copyable';
 /* eslint-disable-next-line no-unused-vars */
-import {IDragTarget} from './interfaces/i_drag_target.js';
+import {IDragTarget} from './interfaces/i_drag_target';
 /* eslint-disable-next-line no-unused-vars */
-import {IFlyout} from './interfaces/i_flyout.js';
+import {IFlyout} from './interfaces/i_flyout';
 /* eslint-disable-next-line no-unused-vars */
-import {IMetricsManager} from './interfaces/i_metrics_manager.js';
+import {IMetricsManager} from './interfaces/i_metrics_manager';
 /* eslint-disable-next-line no-unused-vars */
-import {IToolbox} from './interfaces/i_toolbox.js';
+import {IToolbox} from './interfaces/i_toolbox';
 /* eslint-disable-next-line no-unused-vars */
-import {Cursor} from './keyboard_nav/cursor.js';
+import {Cursor} from './keyboard_nav/cursor';
 /* eslint-disable-next-line no-unused-vars */
-import {Marker} from './keyboard_nav/marker.js';
-import {MarkerManager} from './marker_manager.js';
-import {Options} from './options.js';
-import * as Procedures from './procedures.js';
-import * as registry from './registry.js';
-import * as blockRendering from './renderers/common/block_rendering.js';
+import {Marker} from './keyboard_nav/marker';
+import {MarkerManager} from './marker_manager';
+import {Options} from './options';
+import * as Procedures from './procedures';
+import * as registry from './registry';
+import * as blockRendering from './renderers/common/block_rendering';
 /* eslint-disable-next-line no-unused-vars */
-import {Renderer} from './renderers/common/renderer.js';
+import {Renderer} from './renderers/common/renderer';
 /* eslint-disable-next-line no-unused-vars */
-import {ScrollbarPair} from './scrollbar_pair.js';
-import * as blocks from './serialization/blocks.js';
+import {ScrollbarPair} from './scrollbar_pair';
+import * as blocks from './serialization/blocks';
 /* eslint-disable-next-line no-unused-vars */
-import {Theme} from './theme.js';
-import {Classic} from './theme/classic.js';
-import {ThemeManager} from './theme_manager.js';
-import * as Tooltip from './tooltip.js';
-import {TouchGesture} from './touch_gesture.js';
+import {Theme} from './theme';
+import {Classic} from './theme/classic';
+import {ThemeManager} from './theme_manager';
+import * as Tooltip from './tooltip';
+import {TouchGesture} from './touch_gesture';
 /* eslint-disable-next-line no-unused-vars */
-import {Trashcan} from './trashcan.js';
-import * as utils from './utils.js';
-import * as arrayUtils from './utils/array.js';
-import {Coordinate} from './utils/coordinate.js';
-import * as dom from './utils/dom.js';
+import {Trashcan} from './trashcan';
+import * as utils from './utils';
+import * as arrayUtils from './utils/array';
+import {Coordinate} from './utils/coordinate';
+import * as dom from './utils/dom';
 /* eslint-disable-next-line no-unused-vars */
-import {Metrics} from './utils/metrics.js';
-import {Rect} from './utils/rect.js';
-import {Size} from './utils/size.js';
-import {Svg} from './utils/svg.js';
-import * as svgMath from './utils/svg_math.js';
-import * as toolbox from './utils/toolbox.js';
-import * as userAgent from './utils/useragent.js';
+import {Metrics} from './utils/metrics';
+import {Rect} from './utils/rect';
+import {Size} from './utils/size';
+import {Svg} from './utils/svg';
+import * as svgMath from './utils/svg_math';
+import * as toolbox from './utils/toolbox';
+import * as userAgent from './utils/useragent';
 /* eslint-disable-next-line no-unused-vars */
-import {VariableModel} from './variable_model.js';
-import * as Variables from './variables.js';
-import * as VariablesDynamic from './variables_dynamic.js';
-import * as WidgetDiv from './widgetdiv.js';
-import {Workspace} from './workspace.js';
-import {WorkspaceAudio} from './workspace_audio.js';
+import {VariableModel} from './variable_model';
+import * as Variables from './variables';
+import * as VariablesDynamic from './variables_dynamic';
+import * as WidgetDiv from './widgetdiv';
+import {Workspace} from './workspace';
+import {WorkspaceAudio} from './workspace_audio';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceComment} from './workspace_comment.js';
+import {WorkspaceComment} from './workspace_comment';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceCommentSvg} from './workspace_comment_svg.js';
+import {WorkspaceCommentSvg} from './workspace_comment_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceDragSurfaceSvg} from './workspace_drag_surface_svg.js';
-import * as Xml from './xml.js';
-import {ZoomControls} from './zoom_controls.js';
+import {WorkspaceDragSurfaceSvg} from './workspace_drag_surface_svg';
+import * as Xml from './xml';
+import {ZoomControls} from './zoom_controls';
 
 
 /** Margin around the top/bottom/left/right after a zoomToFit call. */
diff --git a/core/xml.ts b/core/xml.ts
index f4ca89869..a3a974c60 100644
--- a/core/xml.ts
+++ b/core/xml.ts
@@ -12,40 +12,40 @@
  * XML reader and writer.
  * @namespace Blockly.Xml
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.Xml');
 
 // Unused import preserved for side-effects. Remove if unneeded.
-import './comment.js';
+import './comment';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './variables.js';
+import './variables';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './workspace_comment.js';
+import './workspace_comment';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './workspace_comment_svg.js';
+import './workspace_comment_svg';
 
 /* eslint-disable-next-line no-unused-vars */
-import {Block} from './block.js';
+import {Block} from './block';
 /* eslint-disable-next-line no-unused-vars */
-import {BlockSvg} from './block_svg.js';
+import {BlockSvg} from './block_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {Connection} from './connection.js';
-import * as eventUtils from './events/utils.js';
+import {Connection} from './connection';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {Field} from './field.js';
-import {inputTypes} from './input_types.js';
-import * as dom from './utils/dom.js';
-import {Size} from './utils/size.js';
-import * as utilsXml from './utils/xml.js';
+import {Field} from './field';
+import {inputTypes} from './input_types';
+import * as dom from './utils/dom';
+import {Size} from './utils/size';
+import * as utilsXml from './utils/xml';
 /* eslint-disable-next-line no-unused-vars */
-import {VariableModel} from './variable_model.js';
-import * as Variables from './variables.js';
+import {VariableModel} from './variable_model';
+import * as Variables from './variables';
 /* eslint-disable-next-line no-unused-vars */
-import {Workspace} from './workspace.js';
-import {WorkspaceComment} from './workspace_comment.js';
-import {WorkspaceCommentSvg} from './workspace_comment_svg.js';
+import {Workspace} from './workspace';
+import {WorkspaceComment} from './workspace_comment';
+import {WorkspaceCommentSvg} from './workspace_comment_svg';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**
diff --git a/core/zoom_controls.ts b/core/zoom_controls.ts
index bb5215020..1c1ed0990 100644
--- a/core/zoom_controls.ts
+++ b/core/zoom_controls.ts
@@ -12,31 +12,31 @@
  * Object representing a zoom icons.
  * @class
  */
-import * as goog from '../closure/goog/goog.js';
+import * as goog from '../closure/goog/goog';
 goog.declareModuleId('Blockly.ZoomControls');
 
 /* eslint-disable-next-line no-unused-vars */
 // Unused import preserved for side-effects. Remove if unneeded.
-import './metrics_manager.js';
+import './metrics_manager';
 // Unused import preserved for side-effects. Remove if unneeded.
-import './events/events_click.js';
+import './events/events_click';
 
-import * as browserEvents from './browser_events.js';
-import {ComponentManager} from './component_manager.js';
-import * as Css from './css.js';
-import * as eventUtils from './events/utils.js';
+import * as browserEvents from './browser_events';
+import {ComponentManager} from './component_manager';
+import * as Css from './css';
+import * as eventUtils from './events/utils';
 /* eslint-disable-next-line no-unused-vars */
-import {IPositionable} from './interfaces/i_positionable.js';
-import {UiMetrics} from './metrics_manager.js';
-import * as uiPosition from './positionable_helpers.js';
-import {SPRITE} from './sprites.js';
-import * as Touch from './touch.js';
-import * as dom from './utils/dom.js';
-import {Rect} from './utils/rect.js';
-import {Size} from './utils/size.js';
-import {Svg} from './utils/svg.js';
+import {IPositionable} from './interfaces/i_positionable';
+import {UiMetrics} from './metrics_manager';
+import * as uiPosition from './positionable_helpers';
+import {SPRITE} from './sprites';
+import * as Touch from './touch';
+import * as dom from './utils/dom';
+import {Rect} from './utils/rect';
+import {Size} from './utils/size';
+import {Svg} from './utils/svg';
 /* eslint-disable-next-line no-unused-vars */
-import {WorkspaceSvg} from './workspace_svg.js';
+import {WorkspaceSvg} from './workspace_svg';
 
 
 /**