diff --git a/core/requires.js b/core/requires.js
index cc67f564a..fc6575fd5 100644
--- a/core/requires.js
+++ b/core/requires.js
@@ -81,3 +81,5 @@ goog.require('Blockly.zelos.Renderer');
 // Blockly Themes.
 // Classic is the default theme.
 goog.require('Blockly.Themes.Classic');
+
+goog.require('Blockly.serialization.blocks');
diff --git a/core/serialization/blocks.js b/core/serialization/blocks.js
new file mode 100644
index 000000000..cefdb3317
--- /dev/null
+++ b/core/serialization/blocks.js
@@ -0,0 +1,114 @@
+/**
+ * @license
+ * Copyright 2021 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Handles serializing blocks to plain JavaScript objects only
+ *     containing state.
+ */
+'use strict';
+
+goog.module('Blockly.serialization.blocks');
+goog.module.declareLegacyNamespace();
+
+
+// TODO: Remove this once lint is fixed.
+/* eslint-disable no-use-before-define */
+
+/**
+ * Represents the state of a given block.
+ * @typedef {{
+ *     type: string,
+ *     id: string,
+ *     x: (number|undefined),
+ *     y: (number|undefined),
+ *     collapsed: (boolean|undefined),
+ *     disabled: (boolean|undefined),
+ *     editable: (boolean|undefined),
+ *     deletable: (boolean|undefined),
+ *     movable: (boolean|undefined),
+ *     inline: (boolean|undefined),
+ *     data: (string|undefined),
+ * }}
+ */
+var State;
+exports.State = State;
+
+/**
+ * Returns the state of the given block as a plain JavaScript object.
+ * @param {!Blockly.Block} block The block to serialize.
+ * @param {{addCoordinates: (boolean|undefined)}=} param1
+ *     addCoordinates: If true the coordinates of the block are added to the
+ *       serialized state. False by default.
+ * @return {?State} The serialized state of the
+ *     block, or null if the block could not be serialied (eg it was an
+ *     insertion marker).
+ */
+const save = function(block, {addCoordinates = false} = {}) {
+  if (block.isInsertionMarker()) {
+    return null;
+  }
+
+  const state = {
+    'type': block.type,
+    'id': block.id
+  };
+
+  if (addCoordinates) {
+    addCoords(block, state);
+  }
+  addAttributes(block, state);
+
+  return state;
+};
+exports.save = save;
+
+/**
+ * Adds attributes to the given state object based on the state of the block.
+ * Eg collapsed, disabled, editable, etc.
+ * @param {!Blockly.Block} block The block to base the attributes on.
+ * @param {!State} state The state object to append
+ *     to.
+ */
+const addAttributes = function(block, state) {
+  if (block.isCollapsed()) {
+    state['collapsed'] = true;
+  }
+  if (!block.isEnabled()) {
+    state['enabled'] = false;
+  }
+  if (!block.isEditable()) {
+    state['editable'] = false;
+  }
+  if (!block.isDeletable() && !block.isShadow()) {
+    state['deletable'] = false;
+  }
+  if (!block.isMovable() && !block.isShadow()) {
+    state['movable'] = false;
+  }
+
+  if (block.inputsInline !== undefined &&
+      block.inputsInline !== block.inputsInlineDefault) {
+    state['inline'] = block.inputsInline;
+  }
+
+  // Data is a nullable string, so we don't need to worry about falsy values.
+  if (block.data) {
+    state['data'] = block.data;
+  }
+};
+
+/**
+ * Adds the coordinates of the given block to the given state object.
+ * @param {!Blockly.Block} block The block to base the coordinates on
+ * @param {!State} state The state object to append
+ *     to
+ */
+const addCoords = function(block, state) {
+  const workspace = block.workspace;
+  const xy = block.getRelativeToSurfaceXY();
+  state['x'] = Math.round(workspace.RTL ? workspace.getWidth() - xy.x : xy.x);
+  state['y'] = Math.round(xy.y);
+};
diff --git a/core/serialization/serialization.js b/core/serialization/serialization.js
new file mode 100644
index 000000000..c53a2eb64
--- /dev/null
+++ b/core/serialization/serialization.js
@@ -0,0 +1,18 @@
+/**
+ * @license
+ * Copyright 2021 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Contains top-level functions for serialization of the workspace
+ *     to JavaScript objects.
+ */
+'use strict';
+
+/**
+ * The top level namespace for JavaScript Object serialization.
+ * @namespace Blockly.serialization
+ */
+goog.module('Blockly.serialization');
+goog.module.declareLegacyNamespace();
diff --git a/tests/deps.js b/tests/deps.js
index 64284f839..bf85399f8 100644
--- a/tests/deps.js
+++ b/tests/deps.js
@@ -193,9 +193,11 @@ goog.addDependency('../../core/renderers/zelos/measurables/row_elements.js', ['B
 goog.addDependency('../../core/renderers/zelos/measurables/top_row.js', ['Blockly.zelos.TopRow'], ['Blockly.blockRendering.TopRow', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/renderers/zelos/path_object.js', ['Blockly.zelos.PathObject'], ['Blockly.blockRendering.PathObject', 'Blockly.utils.Svg', 'Blockly.utils.dom', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/renderers/zelos/renderer.js', ['Blockly.zelos.Renderer'], ['Blockly.InsertionMarkerManager', 'Blockly.blockRendering', 'Blockly.blockRendering.Renderer', 'Blockly.connectionTypes', 'Blockly.utils.object', 'Blockly.zelos.ConstantProvider', 'Blockly.zelos.Drawer', 'Blockly.zelos.MarkerSvg', 'Blockly.zelos.PathObject', 'Blockly.zelos.RenderInfo'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/requires.js', ['Blockly.requires'], ['Blockly', 'Blockly.Comment', 'Blockly.ContextMenuItems', 'Blockly.FieldAngle', 'Blockly.FieldCheckbox', 'Blockly.FieldColour', 'Blockly.FieldDropdown', 'Blockly.FieldImage', 'Blockly.FieldLabelSerializable', 'Blockly.FieldMultilineInput', 'Blockly.FieldNumber', 'Blockly.FieldTextInput', 'Blockly.FieldVariable', 'Blockly.FlyoutButton', 'Blockly.Generator', 'Blockly.HorizontalFlyout', 'Blockly.Mutator', 'Blockly.ShortcutItems', 'Blockly.Themes.Classic', 'Blockly.Toolbox', 'Blockly.Trashcan', 'Blockly.VariablesDynamic', 'Blockly.VerticalFlyout', 'Blockly.Warning', 'Blockly.ZoomControls', 'Blockly.geras.Renderer', 'Blockly.thrasos.Renderer', 'Blockly.zelos.Renderer']);
+goog.addDependency('../../core/requires.js', ['Blockly.requires'], ['Blockly', 'Blockly.Comment', 'Blockly.ContextMenuItems', 'Blockly.FieldAngle', 'Blockly.FieldCheckbox', 'Blockly.FieldColour', 'Blockly.FieldDropdown', 'Blockly.FieldImage', 'Blockly.FieldLabelSerializable', 'Blockly.FieldMultilineInput', 'Blockly.FieldNumber', 'Blockly.FieldTextInput', 'Blockly.FieldVariable', 'Blockly.FlyoutButton', 'Blockly.Generator', 'Blockly.HorizontalFlyout', 'Blockly.Mutator', 'Blockly.ShortcutItems', 'Blockly.Themes.Classic', 'Blockly.Toolbox', 'Blockly.Trashcan', 'Blockly.VariablesDynamic', 'Blockly.VerticalFlyout', 'Blockly.Warning', 'Blockly.ZoomControls', 'Blockly.geras.Renderer', 'Blockly.serialization.blocks', 'Blockly.thrasos.Renderer', 'Blockly.zelos.Renderer']);
 goog.addDependency('../../core/scrollbar.js', ['Blockly.Scrollbar'], ['Blockly.Touch', 'Blockly.browserEvents', 'Blockly.utils', 'Blockly.utils.Coordinate', 'Blockly.utils.Svg', 'Blockly.utils.dom'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/scrollbar_pair.js', ['Blockly.ScrollbarPair'], ['Blockly.Events', 'Blockly.Scrollbar', 'Blockly.utils.Svg', 'Blockly.utils.dom'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/serialization/blocks.js', ['Blockly.serialization.blocks'], [], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/serialization/serialization.js', ['Blockly.serialization'], [], {'module': 'goog'});
 goog.addDependency('../../core/shortcut_items.js', ['Blockly.ShortcutItems'], ['Blockly.Gesture', 'Blockly.ShortcutRegistry', 'Blockly.clipboard', 'Blockly.common', 'Blockly.utils.KeyCodes'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/shortcut_registry.js', ['Blockly.ShortcutRegistry'], ['Blockly.utils.KeyCodes', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/theme.js', ['Blockly.Theme'], ['Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
diff --git a/tests/deps.mocha.js b/tests/deps.mocha.js
index 85a06ac1a..d0b49e0a5 100644
--- a/tests/deps.mocha.js
+++ b/tests/deps.mocha.js
@@ -193,9 +193,11 @@ goog.addDependency('../../core/renderers/zelos/measurables/row_elements.js', ['B
 goog.addDependency('../../core/renderers/zelos/measurables/top_row.js', ['Blockly.zelos.TopRow'], ['Blockly.blockRendering.TopRow', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/renderers/zelos/path_object.js', ['Blockly.zelos.PathObject'], ['Blockly.blockRendering.PathObject', 'Blockly.utils.Svg', 'Blockly.utils.dom', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/renderers/zelos/renderer.js', ['Blockly.zelos.Renderer'], ['Blockly.InsertionMarkerManager', 'Blockly.blockRendering', 'Blockly.blockRendering.Renderer', 'Blockly.connectionTypes', 'Blockly.utils.object', 'Blockly.zelos.ConstantProvider', 'Blockly.zelos.Drawer', 'Blockly.zelos.MarkerSvg', 'Blockly.zelos.PathObject', 'Blockly.zelos.RenderInfo'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/requires.js', ['Blockly.requires'], ['Blockly', 'Blockly.Comment', 'Blockly.ContextMenuItems', 'Blockly.FieldAngle', 'Blockly.FieldCheckbox', 'Blockly.FieldColour', 'Blockly.FieldDropdown', 'Blockly.FieldImage', 'Blockly.FieldLabelSerializable', 'Blockly.FieldMultilineInput', 'Blockly.FieldNumber', 'Blockly.FieldTextInput', 'Blockly.FieldVariable', 'Blockly.FlyoutButton', 'Blockly.Generator', 'Blockly.HorizontalFlyout', 'Blockly.Mutator', 'Blockly.ShortcutItems', 'Blockly.Themes.Classic', 'Blockly.Toolbox', 'Blockly.Trashcan', 'Blockly.VariablesDynamic', 'Blockly.VerticalFlyout', 'Blockly.Warning', 'Blockly.ZoomControls', 'Blockly.geras.Renderer', 'Blockly.thrasos.Renderer', 'Blockly.zelos.Renderer']);
+goog.addDependency('../../core/requires.js', ['Blockly.requires'], ['Blockly', 'Blockly.Comment', 'Blockly.ContextMenuItems', 'Blockly.FieldAngle', 'Blockly.FieldCheckbox', 'Blockly.FieldColour', 'Blockly.FieldDropdown', 'Blockly.FieldImage', 'Blockly.FieldLabelSerializable', 'Blockly.FieldMultilineInput', 'Blockly.FieldNumber', 'Blockly.FieldTextInput', 'Blockly.FieldVariable', 'Blockly.FlyoutButton', 'Blockly.Generator', 'Blockly.HorizontalFlyout', 'Blockly.Mutator', 'Blockly.ShortcutItems', 'Blockly.Themes.Classic', 'Blockly.Toolbox', 'Blockly.Trashcan', 'Blockly.VariablesDynamic', 'Blockly.VerticalFlyout', 'Blockly.Warning', 'Blockly.ZoomControls', 'Blockly.geras.Renderer', 'Blockly.serialization.blocks', 'Blockly.thrasos.Renderer', 'Blockly.zelos.Renderer']);
 goog.addDependency('../../core/scrollbar.js', ['Blockly.Scrollbar'], ['Blockly.Touch', 'Blockly.browserEvents', 'Blockly.utils', 'Blockly.utils.Coordinate', 'Blockly.utils.Svg', 'Blockly.utils.dom'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/scrollbar_pair.js', ['Blockly.ScrollbarPair'], ['Blockly.Events', 'Blockly.Scrollbar', 'Blockly.utils.Svg', 'Blockly.utils.dom'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/serialization/blocks.js', ['Blockly.serialization.blocks'], [], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../core/serialization/serialization.js', ['Blockly.serialization'], [], {'module': 'goog'});
 goog.addDependency('../../core/shortcut_items.js', ['Blockly.ShortcutItems'], ['Blockly.Gesture', 'Blockly.ShortcutRegistry', 'Blockly.clipboard', 'Blockly.common', 'Blockly.utils.KeyCodes'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/shortcut_registry.js', ['Blockly.ShortcutRegistry'], ['Blockly.utils.KeyCodes', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/theme.js', ['Blockly.Theme'], ['Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
@@ -328,6 +330,7 @@ goog.addDependency('../../tests/mocha/generator_test.js', ['Blockly.test.generat
 goog.addDependency('../../tests/mocha/gesture_test.js', ['Blockly.test.gesture'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/input_test.js', ['Blockly.test.input'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/insertion_marker_test.js', ['Blockly.test.insertionMarker'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/jso_serialization_test.js', ['Blockly.test.jsoSerialization'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/json_test.js', ['Blockly.test.json'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/keydown_test.js', ['Blockly.test.keydown'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/logic_ternary_test.js', ['Blockly.test.logicTernary'], ['Blockly.test.helpers'], {'lang': 'es6', 'module': 'goog'});
diff --git a/tests/mocha/index.html b/tests/mocha/index.html
index 81ba4476e..ab34e2c8e 100644
--- a/tests/mocha/index.html
+++ b/tests/mocha/index.html
@@ -82,6 +82,7 @@
       goog.require('Blockly.test.gesture');
       goog.require('Blockly.test.input');
       goog.require('Blockly.test.insertionMarker');
+      goog.require('Blockly.test.jsoSerialization');
       goog.require('Blockly.test.json');
       goog.require('Blockly.test.keydown');
       goog.require('Blockly.test.logicTernary');
diff --git a/tests/mocha/jso_serialization_test.js b/tests/mocha/jso_serialization_test.js
new file mode 100644
index 000000000..2b24d170c
--- /dev/null
+++ b/tests/mocha/jso_serialization_test.js
@@ -0,0 +1,241 @@
+/**
+ * @license
+ * Copyright 2021 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+goog.module('Blockly.test.jsoSerialization');
+
+const {defineStackBlock, defineRowBlock, defineStatementBlock, createGenUidStubWithReturns, sharedTestSetup, sharedTestTeardown, workspaceTeardown} = goog.require('Blockly.test.helpers');
+
+
+suite('JSO', function() {
+  setup(function() {
+    sharedTestSetup.call(this);
+    this.workspace = new Blockly.Workspace();
+
+    defineStackBlock();
+    defineRowBlock();
+    defineStatementBlock();
+
+    createGenUidStubWithReturns(new Array(10).fill().map((_, i) => 'id' + i));
+  });
+
+  teardown(function() {
+    workspaceTeardown.call(this, this.workspace);
+    sharedTestTeardown.call(this);
+  });
+
+  suite('Blocks', function() {
+    test('Null on insertionMarkers', function() {
+      const block = this.workspace.newBlock('row_block');
+      block.setInsertionMarker(true);
+      const jso = Blockly.serialization.blocks.save(block);
+      chai.assert.isNull(jso);
+    });
+
+    suite('Save Single Block', function() {
+
+      function assertProperty(obj, property, value) {
+        chai.assert.equal(obj[property], value);
+      }
+
+      function assertNoProperty(obj, property) {
+        assertProperty(obj, property, undefined);
+      }
+
+      test('Basic', function() {
+        const block = this.workspace.newBlock('row_block');
+        const jso = Blockly.serialization.blocks.save(block);
+        assertProperty(jso, 'type', 'row_block');
+        assertProperty(jso, 'id', 'id0');
+      });
+
+      suite('Attributes', function() {
+        suite('Collapsed', function() {
+          test('True', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setCollapsed(true);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertProperty(jso, 'collapsed', true);
+          });
+
+          test('False', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setCollapsed(false);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'collapsed');
+          });
+        });
+
+        suite('Enabled', function() {
+          test('False', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setEnabled(false);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertProperty(jso, 'enabled', false);
+          });
+  
+          test('True', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setEnabled(true);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'enabled');
+          });
+        });
+
+        suite('Deletable', function() {
+          test('False', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setDeletable(false);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertProperty(jso, 'deletable', false);
+          });
+
+          test('True', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setDeletable(true);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'deletable');
+          });
+
+          test('False and Shadow', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setDeletable(false);
+            block.setShadow(true);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'deletable');
+          });
+        });
+
+        suite('Movable', function() {
+          test('False', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setMovable(false);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertProperty(jso, 'movable', false);
+          });
+
+          test('True', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setMovable(true);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'movable');
+          });
+
+          test('False and Shadow', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setMovable(false);
+            block.setShadow(true);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'movable');
+          });
+        });
+
+        suite('Editable', function() {
+          test('False', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setEditable(false);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertProperty(jso, 'editable', false);
+          });
+  
+          test('True', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.setEditable(true);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'editable');
+          });
+        });
+
+        suite('Inline', function() {
+          test('True', function() {
+            const block = this.workspace.newBlock('statement_block');
+            block.setInputsInline(true);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertProperty(jso, 'inline', true);
+          });
+
+          test('False', function() {
+            const block = this.workspace.newBlock('statement_block');
+            block.setInputsInline(false);
+            const jso = Blockly.serialization.blocks.save(block);
+            assertProperty(jso, 'inline', false);
+          });
+
+          test('undefined', function() {
+            const block = this.workspace.newBlock('statement_block');
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'inline');
+          });
+
+          test('True, matching default', function() {
+            const block = this.workspace.newBlock('statement_block');
+            block.setInputsInline(true);
+            block.inputsInlineDefault = true;
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'inline');
+          });
+
+          test('False, matching default', function() {
+            const block = this.workspace.newBlock('statement_block');
+            block.setInputsInline(false);
+            block.inputsInlineDefault = false;
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'inline');
+          });
+        });
+
+        suite('Data', function() {
+          test('No data', function() {
+            const block = this.workspace.newBlock('row_block');
+            const jso = Blockly.serialization.blocks.save(block);
+            assertNoProperty(jso, 'data');
+          });
+
+          test('With data', function() {
+            const block = this.workspace.newBlock('row_block');
+            block.data = 'some data';
+            const jso = Blockly.serialization.blocks.save(block);
+            assertProperty(jso, 'data', 'some data');
+          });
+        });
+      });
+
+      suite('Coords', function() {
+        test('No coordinates', function() {
+          const block = this.workspace.newBlock('row_block');
+          const jso = Blockly.serialization.blocks.save(block);
+          assertNoProperty(jso, 'x');
+          assertNoProperty(jso, 'y');
+        });
+
+        test('Simple', function() {
+          const block = this.workspace.newBlock('row_block');
+          block.moveBy(42, 42);
+          const jso =
+              Blockly.serialization.blocks.save(block, {addCoordinates: true});
+          assertProperty(jso, 'x', 42);
+          assertProperty(jso, 'y', 42);
+        });
+
+        test('Negative', function() {
+          const block = this.workspace.newBlock('row_block');
+          block.moveBy(-42, -42);
+          const jso =
+              Blockly.serialization.blocks.save(block, {addCoordinates: true});
+          assertProperty(jso, 'x', -42);
+          assertProperty(jso, 'y', -42);
+        });
+
+        test('Zero', function() {
+          const block = this.workspace.newBlock('row_block');
+          const jso =
+              Blockly.serialization.blocks.save(block, {addCoordinates: true});
+          assertProperty(jso, 'x', 0);
+          assertProperty(jso, 'y', 0);
+        });
+      });
+    });
+  });
+});