diff --git a/aio/content/guide/deprecations.md b/aio/content/guide/deprecations.md
index c056238c3f..ce4ab4314a 100644
--- a/aio/content/guide/deprecations.md
+++ b/aio/content/guide/deprecations.md
@@ -122,6 +122,19 @@ Tip: In the [API reference section](api) of this doc site, deprecated APIs are i
 | --- | ----------- | --------------------- | ----- |
 | [`preserveQueryParams`](api/router/NavigationExtras#preserveQueryParams) | [`queryParamsHandling`](api/router/NavigationExtras#queryParamsHandling) | v4 | none |
 
+{@a platform-webworker}
+### @angular/platform-webworker
+
+| API | Replacement | Deprecation announced | Notes |
+| --- | ----------- | --------------------- | ----- |
+| [All entry points](api/platform-webworker) | none | v8 | See [platform-webworker](#webworker-apps). |
+
+{@a platform-webworker-dynamic}
+### @angular/platform-webworker-dynamic
+
+| API | Replacement | Deprecation announced | Notes |
+| --- | ----------- | --------------------- | ----- |
+| [All entry points](api/platform-webworker-dynamic) | none | v8 | See [platform-webworker](#webworker-apps). |
 
 {@a upgrade}
 ### @angular/upgrade
@@ -380,6 +393,21 @@ Instead, use web workers primarily for offloading CPU intensive, but functionall
 
 
 
+{@a webworker-apps}
+### platform-webworker Angular applications
+
+
+platform-webworker has been around since the initial release of Angular version 2. It began as an experiment to leverage Angular's rendering architecture and try something different: to run an entire web application in a web worker.
+
+We've learned a lot from this experiment, and have come to the conclusion that pushing entire applications to run in a web worker is not a recipe for success for most applications. This is due to a number of unresolved issues, including:
+
+* Poor or non-existent support for web worker APIs in web crawlers/indexers.
+* Poor support in build and bundling tooling.
+
+As a result, as of Angular version 8, we are deprecating the `platform-webworker` APIs in Angular. This consists of both NPM packages, `@angular/platform-webworker` and `@angular/platform-webworker-dynamic`.
+
+Going forward, we will focus our efforts related to web workers around their primary use case of offloading CPU-intensive but not critical work.
+
 {@a removed}
 ## Removed APIs
 
diff --git a/packages/platform-webworker-dynamic/src/platform-webworker-dynamic.ts b/packages/platform-webworker-dynamic/src/platform-webworker-dynamic.ts
index 08f100e41d..68180cfd67 100644
--- a/packages/platform-webworker-dynamic/src/platform-webworker-dynamic.ts
+++ b/packages/platform-webworker-dynamic/src/platform-webworker-dynamic.ts
@@ -16,6 +16,7 @@ export {VERSION} from './version';
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const platformWorkerAppDynamic =
     createPlatformFactory(platformCoreDynamic, 'workerAppDynamic', [
diff --git a/packages/platform-webworker-dynamic/src/version.ts b/packages/platform-webworker-dynamic/src/version.ts
index 9469ebe5e5..91b55934de 100644
--- a/packages/platform-webworker-dynamic/src/version.ts
+++ b/packages/platform-webworker-dynamic/src/version.ts
@@ -16,5 +16,6 @@ import {Version} from '@angular/core';
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const VERSION = new Version('0.0.0-PLACEHOLDER');
diff --git a/packages/platform-webworker/src/platform-webworker.ts b/packages/platform-webworker/src/platform-webworker.ts
index 7dab62437f..ed593eb65b 100644
--- a/packages/platform-webworker/src/platform-webworker.ts
+++ b/packages/platform-webworker/src/platform-webworker.ts
@@ -24,6 +24,7 @@ export {platformWorkerUi} from './worker_render';
  * Bootstraps the worker ui.
  *
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export function bootstrapWorkerUi(
     workerScriptUri: string, customProviders: StaticProvider[] = []): Promise<PlatformRef> {
diff --git a/packages/platform-webworker/src/version.ts b/packages/platform-webworker/src/version.ts
index 9469ebe5e5..91b55934de 100644
--- a/packages/platform-webworker/src/version.ts
+++ b/packages/platform-webworker/src/version.ts
@@ -16,5 +16,6 @@ import {Version} from '@angular/core';
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const VERSION = new Version('0.0.0-PLACEHOLDER');
diff --git a/packages/platform-webworker/src/web_workers/shared/client_message_broker.ts b/packages/platform-webworker/src/web_workers/shared/client_message_broker.ts
index dc974b65e7..0a79ccd883 100644
--- a/packages/platform-webworker/src/web_workers/shared/client_message_broker.ts
+++ b/packages/platform-webworker/src/web_workers/shared/client_message_broker.ts
@@ -12,6 +12,7 @@ import {Serializer, SerializerTypes} from './serializer';
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 @Injectable()
 export class ClientMessageBrokerFactory {
@@ -39,6 +40,7 @@ interface PromiseCompleter {
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export class ClientMessageBroker {
   private _pending = new Map<string, PromiseCompleter>();
diff --git a/packages/platform-webworker/src/web_workers/shared/message_bus.ts b/packages/platform-webworker/src/web_workers/shared/message_bus.ts
index 51cd04e87f..3afa95f327 100644
--- a/packages/platform-webworker/src/web_workers/shared/message_bus.ts
+++ b/packages/platform-webworker/src/web_workers/shared/message_bus.ts
@@ -17,6 +17,7 @@ import {EventEmitter, NgZone} from '@angular/core';
  * by the corresponding MessageBusSource.
  *
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export abstract class MessageBus implements MessageBusSource, MessageBusSink {
   /**
diff --git a/packages/platform-webworker/src/web_workers/shared/serializer.ts b/packages/platform-webworker/src/web_workers/shared/serializer.ts
index 2a47cf7458..7b2d16631f 100644
--- a/packages/platform-webworker/src/web_workers/shared/serializer.ts
+++ b/packages/platform-webworker/src/web_workers/shared/serializer.ts
@@ -12,6 +12,7 @@ import {RenderStore} from './render_store';
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const enum SerializerTypes {
   // RendererType2
diff --git a/packages/platform-webworker/src/web_workers/shared/service_message_broker.ts b/packages/platform-webworker/src/web_workers/shared/service_message_broker.ts
index ba97a1124f..f18d7feaa6 100644
--- a/packages/platform-webworker/src/web_workers/shared/service_message_broker.ts
+++ b/packages/platform-webworker/src/web_workers/shared/service_message_broker.ts
@@ -13,6 +13,7 @@ import {Serializer, SerializerTypes} from '../shared/serializer';
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 @Injectable()
 export class ServiceMessageBrokerFactory {
@@ -40,6 +41,7 @@ export class ServiceMessageBrokerFactory {
  * If that method returns a promise, the UIMessageBroker returns the result to the worker.
  *
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export class ServiceMessageBroker {
   private _sink: EventEmitter<any>;
@@ -91,6 +93,7 @@ export class ServiceMessageBroker {
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export interface ReceivedMessage {
   method: string;
diff --git a/packages/platform-webworker/src/web_workers/ui/location_providers.ts b/packages/platform-webworker/src/web_workers/ui/location_providers.ts
index ac91a2025d..ac35c15f4a 100644
--- a/packages/platform-webworker/src/web_workers/ui/location_providers.ts
+++ b/packages/platform-webworker/src/web_workers/ui/location_providers.ts
@@ -22,6 +22,7 @@ import {MessageBasedPlatformLocation} from './platform_location';
  * A list of {@link Provider}s. To use the router in a Worker enabled application you must
  * include these providers when setting up the render thread.
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const WORKER_UI_LOCATION_PROVIDERS = <StaticProvider[]>[
   {provide: MessageBasedPlatformLocation, deps: [ServiceMessageBrokerFactory,
diff --git a/packages/platform-webworker/src/web_workers/worker/location_providers.ts b/packages/platform-webworker/src/web_workers/worker/location_providers.ts
index 5438cd1bbe..e61ce5cf5b 100644
--- a/packages/platform-webworker/src/web_workers/worker/location_providers.ts
+++ b/packages/platform-webworker/src/web_workers/worker/location_providers.ts
@@ -17,6 +17,7 @@ import {WebWorkerPlatformLocation} from './platform_location';
  * a worker context.
  *
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const WORKER_APP_LOCATION_PROVIDERS = [
   {provide: PlatformLocation, useClass: WebWorkerPlatformLocation}, {
diff --git a/packages/platform-webworker/src/worker_app.ts b/packages/platform-webworker/src/worker_app.ts
index 061ca060ee..987e613586 100644
--- a/packages/platform-webworker/src/worker_app.ts
+++ b/packages/platform-webworker/src/worker_app.ts
@@ -24,6 +24,7 @@ import {WorkerDomAdapter} from './web_workers/worker/worker_adapter';
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const platformWorkerApp = createPlatformFactory(
     platformCore, 'workerApp', [{provide: PLATFORM_ID, useValue: PLATFORM_WORKER_APP_ID}]);
@@ -56,6 +57,7 @@ export function setupWebWorker(): void {
  * The ng module for the worker app side.
  *
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 @NgModule({
   providers: [
diff --git a/packages/platform-webworker/src/worker_render.ts b/packages/platform-webworker/src/worker_render.ts
index f5b3ea5e27..b03dbb7776 100644
--- a/packages/platform-webworker/src/worker_render.ts
+++ b/packages/platform-webworker/src/worker_render.ts
@@ -26,6 +26,7 @@ import {MessageBasedRenderer2} from './web_workers/ui/renderer';
  * and underlying {@link MessageBus} for lower level message passing.
  *
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 @Injectable()
 export class WebWorkerInstance {
@@ -43,6 +44,7 @@ export class WebWorkerInstance {
 
 /**
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const WORKER_SCRIPT = new InjectionToken<string>('WebWorkerScript');
 
@@ -51,6 +53,7 @@ export const WORKER_SCRIPT = new InjectionToken<string>('WebWorkerScript');
  * created.
  *
  * @publicApi
+ * @deprecated platform-webworker is deprecated in Angular and will be removed in version 10
  */
 export const WORKER_UI_STARTABLE_MESSAGING_SERVICE =
     new InjectionToken<({start: () => void})[]>('WorkerRenderStartableMsgService');
diff --git a/tools/public_api_guard/platform-webworker-dynamic/platform-webworker-dynamic.d.ts b/tools/public_api_guard/platform-webworker-dynamic/platform-webworker-dynamic.d.ts
index 8b8e2110a5..f2abbd6e3b 100644
--- a/tools/public_api_guard/platform-webworker-dynamic/platform-webworker-dynamic.d.ts
+++ b/tools/public_api_guard/platform-webworker-dynamic/platform-webworker-dynamic.d.ts
@@ -1,3 +1,5 @@
+/** @deprecated */
 export declare const platformWorkerAppDynamic: (extraProviders?: StaticProvider[] | undefined) => PlatformRef;
 
+/** @deprecated */
 export declare const VERSION: Version;
diff --git a/tools/public_api_guard/platform-webworker/platform-webworker.d.ts b/tools/public_api_guard/platform-webworker/platform-webworker.d.ts
index d9d000f23b..8293c24d7a 100644
--- a/tools/public_api_guard/platform-webworker/platform-webworker.d.ts
+++ b/tools/public_api_guard/platform-webworker/platform-webworker.d.ts
@@ -1,9 +1,12 @@
+/** @deprecated */
 export declare function bootstrapWorkerUi(workerScriptUri: string, customProviders?: StaticProvider[]): Promise<PlatformRef>;
 
+/** @deprecated */
 export declare class ClientMessageBroker {
     runOnService(args: UiArguments, returnType: Type<any> | SerializerTypes | null): Promise<any> | null;
 }
 
+/** @deprecated */
 export declare class ClientMessageBrokerFactory {
     createMessageBroker(channel: string, runInZone?: boolean): ClientMessageBroker;
 }
@@ -14,6 +17,7 @@ export declare class FnArg {
     constructor(value: any, type?: Type<any> | SerializerTypes);
 }
 
+/** @deprecated */
 export declare abstract class MessageBus implements MessageBusSource, MessageBusSink {
     abstract attachToZone(zone: NgZone): void;
     abstract from(channel: string): EventEmitter<any>;
@@ -33,10 +37,12 @@ export interface MessageBusSource {
     initChannel(channel: string, runInZone: boolean): void;
 }
 
+/** @deprecated */
 export declare const platformWorkerApp: (extraProviders?: StaticProvider[] | undefined) => PlatformRef;
 
 export declare const platformWorkerUi: (extraProviders?: StaticProvider[] | undefined) => PlatformRef;
 
+/** @deprecated */
 export interface ReceivedMessage {
     args: any[];
     id: string;
@@ -44,16 +50,19 @@ export interface ReceivedMessage {
     type: string;
 }
 
+/** @deprecated */
 export declare const enum SerializerTypes {
     RENDERER_TYPE_2 = 0,
     PRIMITIVE = 1,
     RENDER_STORE_OBJECT = 2
 }
 
+/** @deprecated */
 export declare class ServiceMessageBroker {
     registerMethod(methodName: string, signature: Array<Type<any> | SerializerTypes> | null, method: (..._: any[]) => Promise<any> | void, returnType?: Type<any> | SerializerTypes): void;
 }
 
+/** @deprecated */
 export declare class ServiceMessageBrokerFactory {
     createMessageBroker(channel: string, runInZone?: boolean): ServiceMessageBroker;
 }
@@ -64,8 +73,10 @@ export declare class UiArguments {
     constructor(method: string, args?: FnArg[] | undefined);
 }
 
+/** @deprecated */
 export declare const VERSION: Version;
 
+/** @deprecated */
 export declare const WORKER_APP_LOCATION_PROVIDERS: ({
     provide: typeof PlatformLocation;
     useClass: typeof WebWorkerPlatformLocation;
@@ -86,7 +97,9 @@ export declare const WORKER_APP_LOCATION_PROVIDERS: ({
     multi?: undefined;
 })[];
 
+/** @deprecated */
 export declare const WORKER_UI_LOCATION_PROVIDERS: StaticProvider[];
 
+/** @deprecated */
 export declare class WorkerAppModule {
 }