diff --git a/src/vs/workbench/api/browser/mainThreadWebview.ts b/src/vs/workbench/api/browser/mainThreadWebview.ts
index 3f5ee9c4f52327f2100b8751768802e57c6058e1..332017e9ee06cb9b7fb3d0017f822a83c348626e 100644
--- a/src/vs/workbench/api/browser/mainThreadWebview.ts
+++ b/src/vs/workbench/api/browser/mainThreadWebview.ts
@@ -536,6 +536,8 @@ namespace HotExitState {
 	export type State = typeof Allowed | typeof NotAllowed | Pending;
 }
 
+const customDocumentFileScheme = 'custom';
+
 class MainThreadCustomEditorModel extends Disposable implements ICustomEditorModel, IWorkingCopy {
 
 	private _hotExitState: HotExitState.State = HotExitState.Allowed;
@@ -556,7 +558,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 	constructor(
 		private readonly _proxy: extHostProtocol.ExtHostWebviewsShape,
 		private readonly _viewType: string,
-		private readonly _resource: URI,
+		private readonly _realResource: URI,
 		private readonly _editable: boolean,
 		@IWorkingCopyService workingCopyService: IWorkingCopyService,
 		@ILabelService private readonly _labelService: ILabelService,
@@ -564,6 +566,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 		@IUndoRedoService private readonly _undoService: IUndoRedoService,
 	) {
 		super();
+
 		if (_editable) {
 			this._register(workingCopyService.registerWorkingCopy(this));
 		}
@@ -571,18 +574,26 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 
 	dispose() {
 		if (this._editable) {
-			this._undoService.removeElements(this.resource);
+			this._undoService.removeElements(this._realResource);
 		}
-		this._proxy.$disposeWebviewCustomEditorDocument(this.resource, this._viewType);
+		this._proxy.$disposeWebviewCustomEditorDocument(this._realResource, this._viewType);
 		super.dispose();
 	}
 
 	//#region IWorkingCopy
 
-	public get resource() { return this._resource; } // custom://viewType/path/file
+	public get resource() {
+		// Make sure each custom editor has a unique resource for backup and edits
+		return URI.from({
+			scheme: customDocumentFileScheme,
+			authority: this._viewType,
+			path: this._realResource.path,
+			query: JSON.stringify(this._realResource.toJSON())
+		});
+	}
 
 	public get name() {
-		return basename(this._labelService.getUriLabel(this._resource));
+		return basename(this._labelService.getUriLabel(this._realResource));
 	}
 
 	public get capabilities(): WorkingCopyCapabilities {
@@ -617,7 +628,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 
 		this._undoService.pushElement({
 			type: UndoRedoElementType.Resource,
-			resource: this.resource,
+			resource: this._realResource,
 			label: label ?? localize('defaultEditLabel', "Edit"),
 			undo: () => this.undo(),
 			redo: () => this.redo(),
@@ -635,7 +646,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 		}
 
 		const undoneEdit = this._edits[this._currentEditIndex];
-		await this._proxy.$undo(this.resource, this.viewType, undoneEdit);
+		await this._proxy.$undo(this._realResource, this.viewType, undoneEdit);
 
 		this.change(() => {
 			--this._currentEditIndex;
@@ -653,7 +664,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 		}
 
 		const redoneEdit = this._edits[this._currentEditIndex + 1];
-		await this._proxy.$redo(this.resource, this.viewType, redoneEdit);
+		await this._proxy.$redo(this._realResource, this.viewType, redoneEdit);
 		this.change(() => {
 			++this._currentEditIndex;
 		});
@@ -668,7 +679,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 			: this._edits.splice(start, toRemove);
 
 		if (removedEdits.length) {
-			this._proxy.$disposeEdits(this.resource, this._viewType, removedEdits);
+			this._proxy.$disposeEdits(this._realResource, this._viewType, removedEdits);
 		}
 	}
 
@@ -700,7 +711,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 			editsToRedo = this._edits.slice(this._currentEditIndex, this._savePoint);
 		}
 
-		this._proxy.$revert(this.resource, this.viewType, { undoneEdits: editsToUndo, redoneEdits: editsToRedo });
+		this._proxy.$revert(this._realResource, this.viewType, { undoneEdits: editsToUndo, redoneEdits: editsToRedo });
 		this.change(() => {
 			this._currentEditIndex = this._savePoint;
 			this.spliceEdits();
@@ -711,7 +722,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 		if (!this._editable) {
 			return false;
 		}
-		await createCancelablePromise(token => this._proxy.$onSave(this.resource, this.viewType, token));
+		await createCancelablePromise(token => this._proxy.$onSave(this._realResource, this.viewType, token));
 		this.change(() => {
 			this._savePoint = this._currentEditIndex;
 		});
@@ -720,7 +731,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 
 	public async saveAs(resource: URI, targetResource: URI, _options?: ISaveOptions): Promise<boolean> {
 		if (this._editable) {
-			await this._proxy.$onSaveAs(this.resource, this.viewType, targetResource);
+			await this._proxy.$onSaveAs(this._realResource, this.viewType, targetResource);
 			this.change(() => {
 				this._savePoint = this._currentEditIndex;
 			});
@@ -749,7 +760,7 @@ class MainThreadCustomEditorModel extends Disposable implements ICustomEditorMod
 
 		const pendingState = new HotExitState.Pending(
 			createCancelablePromise(token =>
-				this._proxy.$backup(this.resource.toJSON(), this.viewType, token)));
+				this._proxy.$backup(this._realResource.toJSON(), this.viewType, token)));
 		this._hotExitState = pendingState;
 
 		try {