diff --git a/src/Umbraco.Web.UI.Client/src/packages/core/extension-registry/extension-api-initializer.ts b/src/Umbraco.Web.UI.Client/src/packages/core/extension-registry/extension-api-initializer.ts
index 2ce2e73efc..41d39f3475 100644
--- a/src/Umbraco.Web.UI.Client/src/packages/core/extension-registry/extension-api-initializer.ts
+++ b/src/Umbraco.Web.UI.Client/src/packages/core/extension-registry/extension-api-initializer.ts
@@ -9,6 +9,7 @@ import {
 import { UmbBaseController, UmbControllerHostElement } from '@umbraco-cms/backoffice/controller-api';
 
 /**
+ * @deprecated
  * Initializes a extensions APIs for a host element.
  * The Extension API will be given one argument, the host element.
  *
@@ -17,6 +18,7 @@ import { UmbBaseController, UmbControllerHostElement } from '@umbraco-cms/backof
  * @param extensionAlias The extension alias to target.
  *
  */
+// TODO: Get rid of this, use Extension Controllers instead.
 export class UmbExtensionApiInitializer<
 	ExtensionType extends string = string,
 	ExtensionManifest extends ManifestBase = SpecificManifestTypeOrManifestBase<ManifestTypes, ExtensionType>,
diff --git a/src/Umbraco.Web.UI.Client/src/packages/core/extension-registry/multi-extensions-api-initializer.ts b/src/Umbraco.Web.UI.Client/src/packages/core/extension-registry/multi-extensions-api-initializer.ts
index c4539cada0..df59ac4f0b 100644
--- a/src/Umbraco.Web.UI.Client/src/packages/core/extension-registry/multi-extensions-api-initializer.ts
+++ b/src/Umbraco.Web.UI.Client/src/packages/core/extension-registry/multi-extensions-api-initializer.ts
@@ -3,6 +3,7 @@ import { umbExtensionsRegistry } from '@umbraco-cms/backoffice/extension-registr
 import { UmbBaseController, UmbControllerHostElement } from '@umbraco-cms/backoffice/controller-api';
 
 /**
+ * @deprecated
  * Initializes multiple extensions APIs for a host element.
  * Extension API will be given one argument, the host element.
  *
@@ -10,6 +11,7 @@ import { UmbBaseController, UmbControllerHostElement } from '@umbraco-cms/backof
  * @param extensionTypes The extension types(strings) to initialize.
  *
  */
+// TODO: Get rid of this, use Extension API Controller instead.
 export class UmbMultiExtensionsApiInitializer extends UmbBaseController {
 	#extensionMap = new Map();