diff --git a/core/interfaces/i_collapsible_toolbox_item.js b/core/interfaces/i_collapsible_toolbox_item.js
new file mode 100644
index 000000000..c92008358
--- /dev/null
+++ b/core/interfaces/i_collapsible_toolbox_item.js
@@ -0,0 +1,45 @@
+/**
+ * @license
+ * Copyright 2020 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview The interface for a collapsible toolbox item.
+ * @author kozbial@google.com (Monica Kozbial)
+ */
+
+'use strict';
+
+goog.provide('Blockly.ICollapsibleToolboxItem');
+
+goog.require('Blockly.IToolboxItem');
+goog.requireType('Blockly.utils.toolbox');
+
+
+/**
+ * Interface for an item in the toolbox that can be collapsed.
+ * @extends {Blockly.ISelectableToolboxItem}
+ * @interface
+ */
+Blockly.ICollapsibleToolboxItem = function() {};
+
+/**
+ * Gets any children toolbox items. (ex. Gets the subcategories)
+ * @return {!Array<!Blockly.IToolboxItem>} The child toolbox items.
+ */
+Blockly.ICollapsibleToolboxItem.prototype.getChildToolboxItems;
+
+/**
+ * Whether the toolbox item is expanded to show its child subcategories.
+ * @return {boolean} True if the toolbox item shows its children, false if it
+ *     is collapsed.
+ * @public
+ */
+Blockly.ICollapsibleToolboxItem.prototype.isExpanded;
+
+/**
+ * Toggles whether or not the toolbox item is expanded.
+ * @public
+ */
+Blockly.ICollapsibleToolboxItem.prototype.toggleExpanded;
diff --git a/core/interfaces/i_selectable_toolbox_item.js b/core/interfaces/i_selectable_toolbox_item.js
new file mode 100644
index 000000000..fb7b8558f
--- /dev/null
+++ b/core/interfaces/i_selectable_toolbox_item.js
@@ -0,0 +1,65 @@
+/**
+ * @license
+ * Copyright 2020 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview The interface for a selectable toolbox item.
+ * @author aschmiedt@google.com (Abby Schmiedt)
+ */
+
+'use strict';
+
+goog.provide('Blockly.ISelectableToolboxItem');
+
+goog.require('Blockly.IToolboxItem');
+goog.requireType('Blockly.utils.toolbox');
+
+
+/**
+ * Interface for an item in the toolbox that can be selected.
+ * @extends {Blockly.IToolboxItem}
+ * @interface
+ */
+Blockly.ISelectableToolboxItem = function() {};
+
+/**
+ * Gets the name of the toolbox item. Used for emitting events.
+ * @return {string} The name of the toolbox item.
+ * @public
+ */
+Blockly.ISelectableToolboxItem.prototype.getName;
+
+/**
+ * Gets the contents of the toolbox item. These are items that are meant to be
+ * displayed in the flyout.
+ * @return {!Blockly.utils.toolbox.FlyoutItemInfoArray|string} The definition
+ *     of items to be displayed in the flyout.
+ * @public
+ */
+Blockly.ISelectableToolboxItem.prototype.getContents;
+
+/**
+ * Sets the current toolbox item as selected.
+ * @param {boolean} _isSelected True if this category is selected, false
+ *     otherwise.
+ * @public
+ */
+Blockly.ISelectableToolboxItem.prototype.setSelected;
+
+/**
+ * Gets the HTML element that is clickable.
+ * The parent toolbox element receives clicks. The parent toolbox will add an ID
+ * to this element so it can pass the onClick event to the correct toolboxItem.
+ * @return {!Element} The HTML element that receives clicks.
+ * @public
+ */
+Blockly.ISelectableToolboxItem.prototype.getClickTarget;
+
+/**
+ * Handles when the toolbox item is clicked.
+ * @param {!Event} _e Click event to handle.
+ * @public
+ */
+Blockly.ISelectableToolboxItem.prototype.onClick;
diff --git a/core/interfaces/i_toolbox_item.js b/core/interfaces/i_toolbox_item.js
index afd6191f7..ce646d376 100644
--- a/core/interfaces/i_toolbox_item.js
+++ b/core/interfaces/i_toolbox_item.js
@@ -11,8 +11,6 @@
 
 'use strict';
 
-goog.provide('Blockly.ICollapsibleToolboxItem');
-goog.provide('Blockly.ISelectableToolboxItem');
 goog.provide('Blockly.IToolboxItem');
 
 goog.requireType('Blockly.utils.toolbox');
@@ -81,77 +79,3 @@ Blockly.IToolboxItem.prototype.isCollapsible;
  * @public
  */
 Blockly.IToolboxItem.prototype.dispose;
-
-/**
- * Interface for an item in the toolbox that can be selected.
- * @extends {Blockly.IToolboxItem}
- * @interface
- */
-Blockly.ISelectableToolboxItem = function() {};
-
-/**
- * Gets the name of the toolbox item. Used for emitting events.
- * @return {string} The name of the toolbox item.
- * @public
- */
-Blockly.ISelectableToolboxItem.prototype.getName;
-
-/**
- * Gets the contents of the toolbox item. These are items that are meant to be
- * displayed in the flyout.
- * @return {!Blockly.utils.toolbox.FlyoutItemInfoArray|string} The definition
- *     of items to be displayed in the flyout.
- * @public
- */
-Blockly.ISelectableToolboxItem.prototype.getContents;
-
-/**
- * Sets the current toolbox item as selected.
- * @param {boolean} _isSelected True if this category is selected, false
- *     otherwise.
- * @public
- */
-Blockly.ISelectableToolboxItem.prototype.setSelected;
-
-/**
- * Gets the HTML element that is clickable.
- * The parent toolbox element receives clicks. The parent toolbox will add an ID
- * to this element so it can pass the onClick event to the correct toolboxItem.
- * @return {!Element} The HTML element that receives clicks.
- * @public
- */
-Blockly.ISelectableToolboxItem.prototype.getClickTarget;
-
-/**
- * Handles when the toolbox item is clicked.
- * @param {!Event} _e Click event to handle.
- * @public
- */
-Blockly.ISelectableToolboxItem.prototype.onClick;
-
-/**
- * Interface for an item in the toolbox that can be collapsed.
- * @extends {Blockly.ISelectableToolboxItem}
- * @interface
- */
-Blockly.ICollapsibleToolboxItem = function() {};
-
-/**
- * Gets any children toolbox items. (ex. Gets the subcategories)
- * @return {!Array<!Blockly.IToolboxItem>} The child toolbox items.
- */
-Blockly.ICollapsibleToolboxItem.prototype.getChildToolboxItems;
-
-/**
- * Whether the toolbox item is expanded to show its child subcategories.
- * @return {boolean} True if the toolbox item shows its children, false if it
- *     is collapsed.
- * @public
- */
-Blockly.ICollapsibleToolboxItem.prototype.isExpanded;
-
-/**
- * Toggles whether or not the toolbox item is expanded.
- * @public
- */
-Blockly.ICollapsibleToolboxItem.prototype.toggleExpanded;