diff --git a/packages/ckeditor5-core/src/editor/editor.js b/packages/ckeditor5-core/src/editor/editor.js
index 95e82222709..6aaef81f485 100644
--- a/packages/ckeditor5-core/src/editor/editor.js
+++ b/packages/ckeditor5-core/src/editor/editor.js
@@ -7,6 +7,8 @@
  * @module core/editor/editor
  */
 
+/* global document */
+
 import Context from '../context';
 import Config from '@ckeditor/ckeditor5-utils/src/config';
 import EditingController from '@ckeditor/ckeditor5-engine/src/controller/editingcontroller';
@@ -175,6 +177,8 @@ export default class Editor {
 		 */
 		this.data = new DataController( this.model, stylesProcessor );
 
+		const sourceElementRoot = config.sourceElementRoot ? config.sourceElementRoot : document;
+
 		/**
 		 * The {@link module:engine/controller/editingcontroller~EditingController editing controller}.
 		 * Controls user input and rendering the content for editing.
@@ -182,7 +186,7 @@ export default class Editor {
 		 * @readonly
 		 * @member {module:engine/controller/editingcontroller~EditingController}
 		 */
-		this.editing = new EditingController( this.model, stylesProcessor );
+		this.editing = new EditingController( this.model, stylesProcessor, sourceElementRoot );
 		this.editing.view.document.bind( 'isReadOnly' ).to( this );
 
 		/**
diff --git a/packages/ckeditor5-engine/src/controller/editingcontroller.js b/packages/ckeditor5-engine/src/controller/editingcontroller.js
index f0d3f8caacd..ec9b0b1ec11 100644
--- a/packages/ckeditor5-engine/src/controller/editingcontroller.js
+++ b/packages/ckeditor5-engine/src/controller/editingcontroller.js
@@ -3,6 +3,8 @@
  * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
  */
 
+/* global document */
+
 /**
  * @module engine/controller/editingcontroller
  */
@@ -33,7 +35,7 @@ export default class EditingController {
 	 * @param {module:engine/model/model~Model} model Editing model.
 	 * @param {module:engine/view/stylesmap~StylesProcessor} stylesProcessor The styles processor instance.
 	 */
-	constructor( model, stylesProcessor ) {
+	constructor( model, stylesProcessor, sourceElementRoot = document ) {
 		/**
 		 * Editor model.
 		 *
@@ -48,7 +50,7 @@ export default class EditingController {
 		 * @readonly
 		 * @member {module:engine/view/view~View}
 		 */
-		this.view = new View( stylesProcessor );
+		this.view = new View( stylesProcessor, sourceElementRoot );
 
 		/**
 		 * Mapper which describes the model-view binding.
diff --git a/packages/ckeditor5-engine/src/view/domconverter.js b/packages/ckeditor5-engine/src/view/domconverter.js
index 4beac20d1ac..8f0acdd016f 100644
--- a/packages/ckeditor5-engine/src/view/domconverter.js
+++ b/packages/ckeditor5-engine/src/view/domconverter.js
@@ -850,7 +850,9 @@ export default class DomConverter {
 	 * @returns {Boolean}
 	 */
 	isDomSelectionBackward( selection ) {
-		if ( selection.isCollapsed ) {
+		// Due to a bug with .isCollapsed always returning true when the selection is from a shadowRoot, also check that the selection
+		// has no ranges or its range is collapsed. More info: https://bugs.chromium.org/p/chromium/issues/detail?id=447523
+		if ( selection.isCollapsed && ( selection.rangeCount === 0 || selection.getRangeAt( 0 ).collapsed ) ) {
 			return false;
 		}
 
diff --git a/packages/ckeditor5-engine/src/view/observer/selectionobserver.js b/packages/ckeditor5-engine/src/view/observer/selectionobserver.js
index 4b3193c7762..636a0efb2a1 100644
--- a/packages/ckeditor5-engine/src/view/observer/selectionobserver.js
+++ b/packages/ckeditor5-engine/src/view/observer/selectionobserver.js
@@ -7,7 +7,7 @@
  * @module engine/view/observer/selectionobserver
  */
 
-/* global setInterval, clearInterval */
+/* global setInterval, clearInterval, document */
 
 import Observer from './observer';
 import MutationObserver from './mutationobserver';
@@ -26,7 +26,7 @@ import { debounce } from 'lodash-es';
  * @extends module:engine/view/observer/observer~Observer
  */
 export default class SelectionObserver extends Observer {
-	constructor( view ) {
+	constructor( view, sourceElementRoot = document ) {
 		super( view );
 
 		/**
@@ -87,6 +87,8 @@ export default class SelectionObserver extends Observer {
 		 * @member {Number} module:engine/view/observer/selectionobserver~SelectionObserver#_loopbackCounter
 		 */
 		this._loopbackCounter = 0;
+
+		this.sourceElementRoot = sourceElementRoot;
 	}
 
 	/**
@@ -135,7 +137,12 @@ export default class SelectionObserver extends Observer {
 
 		// If there were mutations then the view will be re-rendered by the mutation observer and selection
 		// will be updated, so selections will equal and event will not be fired, as expected.
-		const domSelection = domDocument.defaultView.getSelection();
+		let domSelection;
+		if ( this.sourceElementRoot === domDocument ) {
+			domSelection = domDocument.defaultView.getSelection();
+		} else {
+			domSelection = this.sourceElementRoot.getSelection();
+		}
 		const newViewSelection = this.domConverter.domSelectionToView( domSelection );
 
 		// Do not convert selection change if the new view selection has no ranges in it.
diff --git a/packages/ckeditor5-engine/src/view/view.js b/packages/ckeditor5-engine/src/view/view.js
index 15fdcb4961c..69b51e71cf8 100644
--- a/packages/ckeditor5-engine/src/view/view.js
+++ b/packages/ckeditor5-engine/src/view/view.js
@@ -3,6 +3,8 @@
  * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
  */
 
+/* global document */
+
 /**
  * @module engine/view/view
  */
@@ -65,7 +67,7 @@ export default class View {
 	/**
 	 * @param {module:engine/view/stylesmap~StylesProcessor} stylesProcessor The styles processor instance.
 	 */
-	constructor( stylesProcessor ) {
+	constructor( stylesProcessor, sourceElementRoot = document ) {
 		/**
 		 * Instance of the {@link module:engine/view/document~Document} associated with this view controller.
 		 *
@@ -179,7 +181,7 @@ export default class View {
 
 		// Add default observers.
 		this.addObserver( MutationObserver );
-		this.addObserver( SelectionObserver );
+		this.addObserver( SelectionObserver, sourceElementRoot );
 		this.addObserver( FocusObserver );
 		this.addObserver( KeyObserver );
 		this.addObserver( FakeSelectionObserver );
@@ -333,14 +335,14 @@ export default class View {
 	 * Should create an instance inheriting from {@link module:engine/view/observer/observer~Observer}.
 	 * @returns {module:engine/view/observer/observer~Observer} Added observer instance.
 	 */
-	addObserver( Observer ) {
+	addObserver( Observer, sourceElementRoot ) {
 		let observer = this._observers.get( Observer );
 
 		if ( observer ) {
 			return observer;
 		}
 
-		observer = new Observer( this );
+		observer = new Observer( this, sourceElementRoot );
 
 		this._observers.set( Observer, observer );