diff --git a/src/client/accessibility.ts b/src/client/accessibility.ts
index 63c938a316dad..4af1336ccc41d 100644
--- a/src/client/accessibility.ts
+++ b/src/client/accessibility.ts
@@ -17,6 +17,7 @@
 
 import * as channels from '../protocol/channels';
 import { ElementHandle } from './elementHandle';
+import * as api from '../../types/types';
 
 type SerializedAXNode = Omit<channels.AXNode, 'valueString' | 'valueNumber' | 'children' | 'checked' | 'pressed'> & {
   value?: string|number,
@@ -38,7 +39,7 @@ function axNodeFromProtocol(axNode: channels.AXNode): SerializedAXNode {
   return result;
 }
 
-export class Accessibility {
+export class Accessibility implements api.Accessibility {
   private _channel: channels.PageChannel;
 
   constructor(channel: channels.PageChannel) {
diff --git a/src/client/browser.ts b/src/client/browser.ts
index 1af06ba248579..52f24ee270138 100644
--- a/src/client/browser.ts
+++ b/src/client/browser.ts
@@ -21,8 +21,9 @@ import { ChannelOwner } from './channelOwner';
 import { Events } from './events';
 import { BrowserContextOptions } from './types';
 import { isSafeCloseError } from '../utils/errors';
+import * as api from '../../types/types';
 
-export class Browser extends ChannelOwner<channels.BrowserChannel, channels.BrowserInitializer> {
+export class Browser extends ChannelOwner<channels.BrowserChannel, channels.BrowserInitializer> implements api.Browser {
   readonly _contexts = new Set<BrowserContext>();
   private _isConnected = true;
   private _closedPromise: Promise<void>;
diff --git a/src/client/browserContext.ts b/src/client/browserContext.ts
index ea6ef97a988a7..456476f4f51a2 100644
--- a/src/client/browserContext.ts
+++ b/src/client/browserContext.ts
@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-import { Page, BindingCall, FunctionWithSource } from './page';
+import { Page, BindingCall } from './page';
 import * as network from './network';
 import * as channels from '../protocol/channels';
 import * as util from 'util';
@@ -30,16 +30,18 @@ import { URLMatch, Headers, WaitForEventOptions, BrowserContextOptions, StorageS
 import { isUnderTest, headersObjectToArray, mkdirIfNeeded } from '../utils/utils';
 import { isSafeCloseError } from '../utils/errors';
 import { serializeArgument } from './jsHandle';
+import * as api from '../../types/types';
+import * as structs from '../../types/structs';
 
 const fsWriteFileAsync = util.promisify(fs.writeFile.bind(fs));
 const fsReadFileAsync = util.promisify(fs.readFile.bind(fs));
 
-export class BrowserContext extends ChannelOwner<channels.BrowserContextChannel, channels.BrowserContextInitializer> {
+export class BrowserContext extends ChannelOwner<channels.BrowserContextChannel, channels.BrowserContextInitializer> implements api.BrowserContext {
   _pages = new Set<Page>();
   private _routes: { url: URLMatch, handler: network.RouteHandler }[] = [];
   readonly _browser: Browser | null = null;
   readonly _browserName: string;
-  readonly _bindings = new Map<string, FunctionWithSource>();
+  readonly _bindings = new Map<string, (source: structs.BindingSource, ...args: any[]) => any>();
   _timeoutSettings = new TimeoutSettings();
   _ownerPage: Page | undefined;
   private _closedPromise: Promise<void>;
@@ -182,7 +184,7 @@ export class BrowserContext extends ChannelOwner<channels.BrowserContextChannel,
     });
   }
 
-  async exposeBinding(name: string, playwrightBinding: FunctionWithSource, options: { handle?: boolean } = {}): Promise<void> {
+  async exposeBinding(name: string, playwrightBinding: (source: structs.BindingSource, ...args: any[]) => any, options: { handle?: boolean } = {}): Promise<void> {
     return this._wrapApiCall('browserContext.exposeBinding', async () => {
       await this._channel.exposeBinding({ name, needsHandle: options.handle });
       this._bindings.set(name, playwrightBinding);
@@ -192,7 +194,7 @@ export class BrowserContext extends ChannelOwner<channels.BrowserContextChannel,
   async exposeFunction(name: string, playwrightFunction: Function): Promise<void> {
     return this._wrapApiCall('browserContext.exposeFunction', async () => {
       await this._channel.exposeBinding({ name });
-      const binding: FunctionWithSource = (source, ...args) => playwrightFunction(...args);
+      const binding = (source: structs.BindingSource, ...args: any[]) => playwrightFunction(...args);
       this._bindings.set(name, binding);
     });
   }
diff --git a/src/client/browserType.ts b/src/client/browserType.ts
index fb79d7a0917ac..4966101e66332 100644
--- a/src/client/browserType.ts
+++ b/src/client/browserType.ts
@@ -32,19 +32,21 @@ import { assert, makeWaitForNextTask, mkdirIfNeeded } from '../utils/utils';
 import { SelectorsOwner, sharedSelectors } from './selectors';
 import { kBrowserClosedError } from '../utils/errors';
 import { Stream } from './stream';
+import * as api from '../../types/types';
 
 export interface BrowserServerLauncher {
-  launchServer(options?: LaunchServerOptions): Promise<BrowserServer>;
+  launchServer(options?: LaunchServerOptions): Promise<api.BrowserServer>;
 }
 
-export interface BrowserServer {
+// This is here just for api generation and checking.
+export interface BrowserServer extends api.BrowserServer {
   process(): ChildProcess;
   wsEndpoint(): string;
   close(): Promise<void>;
   kill(): Promise<void>;
 }
 
-export class BrowserType extends ChannelOwner<channels.BrowserTypeChannel, channels.BrowserTypeInitializer> {
+export class BrowserType extends ChannelOwner<channels.BrowserTypeChannel, channels.BrowserTypeInitializer> implements api.BrowserType<api.Browser> {
   private _timeoutSettings = new TimeoutSettings();
   _serverLauncher?: BrowserServerLauncher;
 
@@ -83,7 +85,7 @@ export class BrowserType extends ChannelOwner<channels.BrowserTypeChannel, chann
     }, logger);
   }
 
-  async launchServer(options: LaunchServerOptions = {}): Promise<BrowserServer> {
+  async launchServer(options: LaunchServerOptions = {}): Promise<api.BrowserServer> {
     if (!this._serverLauncher)
       throw new Error('Launching server is not supported');
     return this._serverLauncher.launchServer(options);
diff --git a/src/client/cdpSession.ts b/src/client/cdpSession.ts
index c3b792395030e..739a5e1c4e53e 100644
--- a/src/client/cdpSession.ts
+++ b/src/client/cdpSession.ts
@@ -17,8 +17,9 @@
 import * as channels from '../protocol/channels';
 import { ChannelOwner } from './channelOwner';
 import { Protocol } from '../server/chromium/protocol';
+import * as api from '../../types/types';
 
-export class CDPSession extends ChannelOwner<channels.CDPSessionChannel, channels.CDPSessionInitializer> {
+export class CDPSession extends ChannelOwner<channels.CDPSessionChannel, channels.CDPSessionInitializer> implements api.CDPSession {
   static from(cdpSession: channels.CDPSessionChannel): CDPSession {
     return (cdpSession as any)._object;
   }
diff --git a/src/client/chromiumBrowser.ts b/src/client/chromiumBrowser.ts
index d6646da93ba85..6441477768290 100644
--- a/src/client/chromiumBrowser.ts
+++ b/src/client/chromiumBrowser.ts
@@ -17,8 +17,19 @@
 import { Page } from './page';
 import { CDPSession } from './cdpSession';
 import { Browser } from './browser';
+import * as api from '../../types/types';
+import { ChromiumBrowserContext } from './chromiumBrowserContext';
+import { BrowserContextOptions } from './types';
+
+export class ChromiumBrowser extends Browser implements api.ChromiumBrowser {
+  contexts(): ChromiumBrowserContext[] {
+    return super.contexts() as ChromiumBrowserContext[];
+  }
+
+  newContext(options?: BrowserContextOptions): Promise<ChromiumBrowserContext> {
+    return super.newContext(options) as Promise<ChromiumBrowserContext>;
+  }
 
-export class ChromiumBrowser extends Browser {
   async newBrowserCDPSession(): Promise<CDPSession> {
     return this._wrapApiCall('chromiumBrowser.newBrowserCDPSession', async () => {
       return CDPSession.from((await this._channel.crNewBrowserCDPSession()).session);
diff --git a/src/client/chromiumBrowserContext.ts b/src/client/chromiumBrowserContext.ts
index 1f9b0ccb68001..a7bc1ae3f1d0c 100644
--- a/src/client/chromiumBrowserContext.ts
+++ b/src/client/chromiumBrowserContext.ts
@@ -22,8 +22,9 @@ import { CDPSession } from './cdpSession';
 import { Events } from './events';
 import { Worker } from './worker';
 import { BrowserContext } from './browserContext';
+import * as api from '../../types/types';
 
-export class ChromiumBrowserContext extends BrowserContext {
+export class ChromiumBrowserContext extends BrowserContext implements api.ChromiumBrowserContext {
   _backgroundPages = new Set<Page>();
   _serviceWorkers = new Set<Worker>();
 
diff --git a/src/client/chromiumCoverage.ts b/src/client/chromiumCoverage.ts
index 472e0ac6d1b4f..1420eaf0528e1 100644
--- a/src/client/chromiumCoverage.ts
+++ b/src/client/chromiumCoverage.ts
@@ -15,8 +15,9 @@
  */
 
 import * as channels from '../protocol/channels';
+import * as api from '../../types/types';
 
-export class ChromiumCoverage {
+export class ChromiumCoverage implements api.ChromiumCoverage {
   private _channel: channels.PageChannel;
 
   constructor(channel: channels.PageChannel) {
diff --git a/src/client/consoleMessage.ts b/src/client/consoleMessage.ts
index 5032d1557647a..9c6d5afeb2b67 100644
--- a/src/client/consoleMessage.ts
+++ b/src/client/consoleMessage.ts
@@ -18,10 +18,11 @@ import * as util from 'util';
 import { JSHandle } from './jsHandle';
 import * as channels from '../protocol/channels';
 import { ChannelOwner } from './channelOwner';
+import * as api from '../../types/types';
 
 type ConsoleMessageLocation = channels.ConsoleMessageInitializer['location'];
 
-export class ConsoleMessage extends ChannelOwner<channels.ConsoleMessageChannel, channels.ConsoleMessageInitializer> {
+export class ConsoleMessage extends ChannelOwner<channels.ConsoleMessageChannel, channels.ConsoleMessageInitializer> implements api.ConsoleMessage {
   static from(message: channels.ConsoleMessageChannel): ConsoleMessage {
     return (message as any)._object;
   }
diff --git a/src/client/dialog.ts b/src/client/dialog.ts
index 458fcfd4e8201..b0e50df60b9e6 100644
--- a/src/client/dialog.ts
+++ b/src/client/dialog.ts
@@ -16,8 +16,9 @@
 
 import * as channels from '../protocol/channels';
 import { ChannelOwner } from './channelOwner';
+import * as api from '../../types/types';
 
-export class Dialog extends ChannelOwner<channels.DialogChannel, channels.DialogInitializer> {
+export class Dialog extends ChannelOwner<channels.DialogChannel, channels.DialogInitializer> implements api.Dialog {
   static from(dialog: channels.DialogChannel): Dialog {
     return (dialog as any)._object;
   }
diff --git a/src/client/download.ts b/src/client/download.ts
index 47da0a009a3f3..5f51c4ed05c7d 100644
--- a/src/client/download.ts
+++ b/src/client/download.ts
@@ -22,8 +22,9 @@ import { Browser } from './browser';
 import { BrowserContext } from './browserContext';
 import * as fs from 'fs';
 import { mkdirIfNeeded } from '../utils/utils';
+import * as api from '../../types/types';
 
-export class Download extends ChannelOwner<channels.DownloadChannel, channels.DownloadInitializer> {
+export class Download extends ChannelOwner<channels.DownloadChannel, channels.DownloadInitializer> implements api.Download {
   private _browser: Browser | null;
 
   static from(download: channels.DownloadChannel): Download {
diff --git a/src/client/electron.ts b/src/client/electron.ts
index 73689adfd8a95..31ec467e5f888 100644
--- a/src/client/electron.ts
+++ b/src/client/electron.ts
@@ -18,12 +18,13 @@ import * as channels from '../protocol/channels';
 import { BrowserContext } from './browserContext';
 import { ChannelOwner } from './channelOwner';
 import { Page } from './page';
-import { serializeArgument, FuncOn, parseResult, SmartHandle, JSHandle } from './jsHandle';
+import { serializeArgument, parseResult, JSHandle } from './jsHandle';
 import { TimeoutSettings } from '../utils/timeoutSettings';
 import { Waiter } from './waiter';
 import { Events } from './events';
 import { WaitForEventOptions, Env, Logger } from './types';
 import { envObjectToArray } from './clientHelper';
+import * as structs from '../../types/structs';
 
 type ElectronOptions = Omit<channels.ElectronLaunchOptions, 'env'> & {
   env?: Env,
@@ -110,17 +111,13 @@ export class ElectronApplication extends ChannelOwner<channels.ElectronApplicati
     return result;
   }
 
-  async evaluate<R, Arg>(pageFunction: FuncOn<any, Arg, R>, arg: Arg): Promise<R>;
-  async evaluate<R>(pageFunction: FuncOn<any, void, R>, arg?: any): Promise<R>;
-  async evaluate<R, Arg>(pageFunction: FuncOn<any, Arg, R>, arg: Arg): Promise<R> {
+  async evaluate<R, Arg>(pageFunction: structs.PageFunctionOn<any, Arg, R>, arg: Arg): Promise<R> {
     const result = await this._channel.evaluateExpression({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
     return parseResult(result.value);
   }
 
-  async evaluateHandle<R, Arg>(pageFunction: FuncOn<any, Arg, R>, arg: Arg): Promise<SmartHandle<R>>;
-  async evaluateHandle<R>(pageFunction: FuncOn<any, void, R>, arg?: any): Promise<SmartHandle<R>>;
-  async evaluateHandle<R, Arg>(pageFunction: FuncOn<any, Arg, R>, arg: Arg): Promise<SmartHandle<R>> {
+  async evaluateHandle<R, Arg>(pageFunction: structs.PageFunctionOn<any, Arg, R>, arg: Arg): Promise<structs.SmartHandle<R>> {
     const result = await this._channel.evaluateExpressionHandle({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
-    return JSHandle.from(result.handle) as SmartHandle<R>;
+    return JSHandle.from(result.handle) as any as structs.SmartHandle<R>;
   }
 }
diff --git a/src/client/elementHandle.ts b/src/client/elementHandle.ts
index ec1726320e22d..64c3ac4aea561 100644
--- a/src/client/elementHandle.ts
+++ b/src/client/elementHandle.ts
@@ -16,7 +16,7 @@
 
 import * as channels from '../protocol/channels';
 import { Frame } from './frame';
-import { FuncOn, JSHandle, serializeArgument, parseResult } from './jsHandle';
+import { JSHandle, serializeArgument, parseResult } from './jsHandle';
 import { ChannelOwner } from './channelOwner';
 import { SelectOption, FilePayload, Rect, SelectOptionOptions } from './types';
 import * as fs from 'fs';
@@ -24,10 +24,12 @@ import * as mime from 'mime';
 import * as path from 'path';
 import * as util from 'util';
 import { assert, isString, mkdirIfNeeded } from '../utils/utils';
+import * as api from '../../types/types';
+import * as structs from '../../types/structs';
 
 const fsWriteFileAsync = util.promisify(fs.writeFile.bind(fs));
 
-export class ElementHandle<T extends Node = Node> extends JSHandle<T> {
+export class ElementHandle<T extends Node = Node> extends JSHandle<T> implements api.ElementHandle {
   readonly _elementChannel: channels.ElementHandleChannel;
 
   static from(handle: channels.ElementHandleChannel): ElementHandle {
@@ -43,8 +45,8 @@ export class ElementHandle<T extends Node = Node> extends JSHandle<T> {
     this._elementChannel = this._channel as channels.ElementHandleChannel;
   }
 
-  asElement(): ElementHandle<T> | null {
-    return this;
+  asElement(): T extends Node ? ElementHandle<T> : null {
+    return this as any;
   }
 
   async ownerFrame(): Promise<Frame | null> {
@@ -121,7 +123,7 @@ export class ElementHandle<T extends Node = Node> extends JSHandle<T> {
     });
   }
 
-  async selectOption(values: string | ElementHandle | SelectOption | string[] | ElementHandle[] | SelectOption[] | null, options: SelectOptionOptions = {}): Promise<string[]> {
+  async selectOption(values: string | api.ElementHandle | SelectOption | string[] | api.ElementHandle[] | SelectOption[] | null, options: SelectOptionOptions = {}): Promise<string[]> {
     return this._wrapApiCall('elementHandle.selectOption', async () => {
       const result = await this._elementChannel.selectOption({ ...convertSelectOptionValues(values), ...options });
       return result.values;
@@ -198,31 +200,27 @@ export class ElementHandle<T extends Node = Node> extends JSHandle<T> {
     });
   }
 
-  async $(selector: string): Promise<ElementHandle<Element> | null> {
+  async $(selector: string): Promise<ElementHandle<SVGElement | HTMLElement> | null> {
     return this._wrapApiCall('elementHandle.$', async () => {
-      return ElementHandle.fromNullable((await this._elementChannel.querySelector({ selector })).element) as ElementHandle<Element> | null;
+      return ElementHandle.fromNullable((await this._elementChannel.querySelector({ selector })).element) as ElementHandle<SVGElement | HTMLElement> | null;
     });
   }
 
-  async $$(selector: string): Promise<ElementHandle<Element>[]> {
+  async $$(selector: string): Promise<ElementHandle<SVGElement | HTMLElement>[]> {
     return this._wrapApiCall('elementHandle.$$', async () => {
       const result = await this._elementChannel.querySelectorAll({ selector });
-      return result.elements.map(h => ElementHandle.from(h) as ElementHandle<Element>);
+      return result.elements.map(h => ElementHandle.from(h) as ElementHandle<SVGElement | HTMLElement>);
     });
   }
 
-  async $eval<R, Arg>(selector: string, pageFunction: FuncOn<Element, Arg, R>, arg: Arg): Promise<R>;
-  async $eval<R>(selector: string, pageFunction: FuncOn<Element, void, R>, arg?: any): Promise<R>;
-  async $eval<R, Arg>(selector: string, pageFunction: FuncOn<Element, Arg, R>, arg: Arg): Promise<R> {
+  async $eval<R, Arg>(selector: string, pageFunction: structs.PageFunctionOn<Element, Arg, R>, arg?: Arg): Promise<R> {
     return this._wrapApiCall('elementHandle.$eval', async () => {
       const result = await this._elementChannel.evalOnSelector({ selector, expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
       return parseResult(result.value);
     });
   }
 
-  async $$eval<R, Arg>(selector: string, pageFunction: FuncOn<Element[], Arg, R>, arg: Arg): Promise<R>;
-  async $$eval<R>(selector: string, pageFunction: FuncOn<Element[], void, R>, arg?: any): Promise<R>;
-  async $$eval<R, Arg>(selector: string, pageFunction: FuncOn<Element[], Arg, R>, arg: Arg): Promise<R> {
+  async $$eval<R, Arg>(selector: string, pageFunction: structs.PageFunctionOn<Element[], Arg, R>, arg?: Arg): Promise<R> {
     return this._wrapApiCall('elementHandle.$$eval', async () => {
       const result = await this._elementChannel.evalOnSelectorAll({ selector, expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
       return parseResult(result.value);
@@ -235,15 +233,17 @@ export class ElementHandle<T extends Node = Node> extends JSHandle<T> {
     });
   }
 
-  async waitForSelector(selector: string, options: channels.ElementHandleWaitForSelectorOptions = {}): Promise<ElementHandle<Element> | null> {
+  waitForSelector(selector: string, options: channels.ElementHandleWaitForSelectorOptions & { state: 'attached' | 'visible' }): Promise<ElementHandle<SVGElement | HTMLElement>>;
+  waitForSelector(selector: string, options?: channels.ElementHandleWaitForSelectorOptions): Promise<ElementHandle<SVGElement | HTMLElement> | null>;
+  async waitForSelector(selector: string, options: channels.ElementHandleWaitForSelectorOptions = {}): Promise<ElementHandle<SVGElement | HTMLElement> | null> {
     return this._wrapApiCall('elementHandle.waitForSelector', async () => {
       const result = await this._elementChannel.waitForSelector({ selector, ...options });
-      return ElementHandle.fromNullable(result.element) as ElementHandle<Element> | null;
+      return ElementHandle.fromNullable(result.element) as ElementHandle<SVGElement | HTMLElement> | null;
     });
   }
 }
 
-export function convertSelectOptionValues(values: string | ElementHandle | SelectOption | string[] | ElementHandle[] | SelectOption[] | null): { elements?: channels.ElementHandleChannel[], options?: SelectOption[] } {
+export function convertSelectOptionValues(values: string | api.ElementHandle | SelectOption | string[] | api.ElementHandle[] | SelectOption[] | null): { elements?: channels.ElementHandleChannel[], options?: SelectOption[] } {
   if (values === null)
     return {};
   if (!Array.isArray(values))
diff --git a/src/client/fileChooser.ts b/src/client/fileChooser.ts
index 923c39e02d519..6f39c30c8c7b6 100644
--- a/src/client/fileChooser.ts
+++ b/src/client/fileChooser.ts
@@ -18,8 +18,9 @@ import { ElementHandle } from './elementHandle';
 import { Page } from './page';
 import { FilePayload } from './types';
 import * as channels from '../protocol/channels';
+import * as api from '../../types/types';
 
-export class FileChooser {
+export class FileChooser implements api.FileChooser {
   private _page: Page;
   private _elementHandle: ElementHandle<Node>;
   private _isMultiple: boolean;
diff --git a/src/client/firefoxBrowser.ts b/src/client/firefoxBrowser.ts
index a55e0f059b115..477b55d9b9378 100644
--- a/src/client/firefoxBrowser.ts
+++ b/src/client/firefoxBrowser.ts
@@ -15,6 +15,7 @@
  */
 
 import { Browser } from './browser';
+import * as api from '../../types/types';
 
-export class FirefoxBrowser extends Browser {
+export class FirefoxBrowser extends Browser implements api.FirefoxBrowser {
 }
diff --git a/src/client/frame.ts b/src/client/frame.ts
index 17fd0f46b0055..7ff7a0d85d49b 100644
--- a/src/client/frame.ts
+++ b/src/client/frame.ts
@@ -19,7 +19,7 @@ import { assert } from '../utils/utils';
 import * as channels from '../protocol/channels';
 import { ChannelOwner } from './channelOwner';
 import { ElementHandle, convertSelectOptionValues, convertInputFiles } from './elementHandle';
-import { assertMaxArguments, JSHandle, Func1, FuncOn, SmartHandle, serializeArgument, parseResult } from './jsHandle';
+import { assertMaxArguments, JSHandle, serializeArgument, parseResult } from './jsHandle';
 import * as fs from 'fs';
 import * as network from './network';
 import * as util from 'util';
@@ -29,6 +29,8 @@ import { Waiter } from './waiter';
 import { Events } from './events';
 import { LifecycleEvent, URLMatch, SelectOption, SelectOptionOptions, FilePayload, WaitForFunctionOptions, kLifecycleEvents } from './types';
 import { urlMatches } from './clientHelper';
+import * as api from '../../types/types';
+import * as structs from '../../types/structs';
 
 const fsReadFileAsync = util.promisify(fs.readFile.bind(fs));
 
@@ -38,7 +40,7 @@ export type WaitForNavigationOptions = {
   url?: URLMatch,
 };
 
-export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameInitializer> {
+export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameInitializer> implements api.Frame {
   _eventEmitter: EventEmitter;
   _loadStates: Set<LifecycleEvent>;
   _parentFrame: Frame | null = null;
@@ -164,29 +166,25 @@ export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameIni
     });
   }
 
-  async evaluateHandle<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<SmartHandle<R>>;
-  async evaluateHandle<R>(pageFunction: Func1<void, R>, arg?: any): Promise<SmartHandle<R>>;
-  async evaluateHandle<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<SmartHandle<R>> {
+  async evaluateHandle<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg): Promise<structs.SmartHandle<R>> {
     assertMaxArguments(arguments.length, 2);
     return this._wrapApiCall(this._apiName('evaluateHandle'), async () => {
       const result = await this._channel.evaluateExpressionHandle({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
-      return JSHandle.from(result.handle) as SmartHandle<R>;
+      return JSHandle.from(result.handle) as any as structs.SmartHandle<R>;
     });
   }
 
-  async _evaluateHandleInUtility<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<SmartHandle<R>>;
-  async _evaluateHandleInUtility<R>(pageFunction: Func1<void, R>, arg?: any): Promise<SmartHandle<R>>;
-  async _evaluateHandleInUtility<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<SmartHandle<R>> {
+  async _evaluateHandleInUtility<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg: Arg): Promise<structs.SmartHandle<R>>;
+  async _evaluateHandleInUtility<R>(pageFunction: structs.PageFunction<void, R>, arg?: any): Promise<structs.SmartHandle<R>>;
+  async _evaluateHandleInUtility<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg): Promise<structs.SmartHandle<R>> {
     assertMaxArguments(arguments.length, 2);
     return this._wrapApiCall(this._apiName('_evaluateHandleInUtility'), async () => {
       const result = await this._channel.evaluateExpressionHandle({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg), world: 'utility' });
-      return JSHandle.from(result.handle) as SmartHandle<R>;
+      return JSHandle.from(result.handle) as any as structs.SmartHandle<R>;
     });
   }
 
-  async evaluate<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<R>;
-  async evaluate<R>(pageFunction: Func1<void, R>, arg?: any): Promise<R>;
-  async evaluate<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<R> {
+  async evaluate<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg): Promise<R> {
     assertMaxArguments(arguments.length, 2);
     return this._wrapApiCall(this._apiName('evaluate'), async () => {
       const result = await this._channel.evaluateExpression({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
@@ -194,9 +192,9 @@ export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameIni
     });
   }
 
-  async _evaluateInUtility<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<R>;
-  async _evaluateInUtility<R>(pageFunction: Func1<void, R>, arg?: any): Promise<R>;
-  async _evaluateInUtility<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<R> {
+  async _evaluateInUtility<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg: Arg): Promise<R>;
+  async _evaluateInUtility<R>(pageFunction: structs.PageFunction<void, R>, arg?: any): Promise<R>;
+  async _evaluateInUtility<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg): Promise<R> {
     assertMaxArguments(arguments.length, 2);
     return this._wrapApiCall(this._apiName('evaluate'), async () => {
       const result = await this._channel.evaluateExpression({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg), world: 'utility' });
@@ -204,21 +202,23 @@ export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameIni
     });
   }
 
-  async $(selector: string): Promise<ElementHandle<Element> | null> {
+  async $(selector: string): Promise<ElementHandle<SVGElement | HTMLElement> | null> {
     return this._wrapApiCall(this._apiName('$'), async () => {
       const result = await this._channel.querySelector({ selector });
-      return ElementHandle.fromNullable(result.element) as ElementHandle<Element> | null;
+      return ElementHandle.fromNullable(result.element) as ElementHandle<SVGElement | HTMLElement> | null;
     });
   }
 
-  async waitForSelector(selector: string, options: channels.FrameWaitForSelectorOptions = {}): Promise<ElementHandle<Element> | null> {
+  waitForSelector(selector: string, options: channels.FrameWaitForSelectorOptions & { state: 'attached' | 'visible' }): Promise<ElementHandle<SVGElement | HTMLElement>>;
+  waitForSelector(selector: string, options?: channels.FrameWaitForSelectorOptions): Promise<ElementHandle<SVGElement | HTMLElement> | null>;
+  async waitForSelector(selector: string, options: channels.FrameWaitForSelectorOptions = {}): Promise<ElementHandle<SVGElement | HTMLElement> | null> {
     return this._wrapApiCall(this._apiName('waitForSelector'), async () => {
       if ((options as any).visibility)
         throw new Error('options.visibility is not supported, did you mean options.state?');
       if ((options as any).waitFor && (options as any).waitFor !== 'visible')
         throw new Error('options.waitFor is not supported, did you mean options.state?');
       const result = await this._channel.waitForSelector({ selector, ...options });
-      return ElementHandle.fromNullable(result.element) as ElementHandle<Element> | null;
+      return ElementHandle.fromNullable(result.element) as ElementHandle<SVGElement | HTMLElement> | null;
     });
   }
 
@@ -228,9 +228,7 @@ export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameIni
     });
   }
 
-  async $eval<R, Arg>(selector: string, pageFunction: FuncOn<Element, Arg, R>, arg: Arg): Promise<R>;
-  async $eval<R>(selector: string, pageFunction: FuncOn<Element, void, R>, arg?: any): Promise<R>;
-  async $eval<R, Arg>(selector: string, pageFunction: FuncOn<Element, Arg, R>, arg: Arg): Promise<R> {
+  async $eval<R, Arg>(selector: string, pageFunction: structs.PageFunctionOn<Element, Arg, R>, arg?: Arg): Promise<R> {
     assertMaxArguments(arguments.length, 3);
     return this._wrapApiCall(this._apiName('$eval'), async () => {
       const result = await this._channel.evalOnSelector({ selector, expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
@@ -238,9 +236,7 @@ export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameIni
     });
   }
 
-  async $$eval<R, Arg>(selector: string, pageFunction: FuncOn<Element[], Arg, R>, arg: Arg): Promise<R>;
-  async $$eval<R>(selector: string, pageFunction: FuncOn<Element[], void, R>, arg?: any): Promise<R>;
-  async $$eval<R, Arg>(selector: string, pageFunction: FuncOn<Element[], Arg, R>, arg: Arg): Promise<R> {
+  async $$eval<R, Arg>(selector: string, pageFunction: structs.PageFunctionOn<Element[], Arg, R>, arg?: Arg): Promise<R> {
     assertMaxArguments(arguments.length, 3);
     return this._wrapApiCall(this._apiName('$$eval'), async () => {
       const result = await this._channel.evalOnSelectorAll({ selector, expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
@@ -248,10 +244,10 @@ export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameIni
     });
   }
 
-  async $$(selector: string): Promise<ElementHandle<Element>[]> {
+  async $$(selector: string): Promise<ElementHandle<SVGElement | HTMLElement>[]> {
     return this._wrapApiCall(this._apiName('$$'), async () => {
       const result = await this._channel.querySelectorAll({ selector });
-      return result.elements.map(e => ElementHandle.from(e) as ElementHandle<Element>);
+      return result.elements.map(e => ElementHandle.from(e) as ElementHandle<SVGElement | HTMLElement>);
     });
   }
 
@@ -372,7 +368,7 @@ export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameIni
     });
   }
 
-  async selectOption(selector: string, values: string | ElementHandle | SelectOption | string[] | ElementHandle[] | SelectOption[] | null, options: SelectOptionOptions = {}): Promise<string[]> {
+  async selectOption(selector: string, values: string | api.ElementHandle | SelectOption | string[] | api.ElementHandle[] | SelectOption[] | null, options: SelectOptionOptions = {}): Promise<string[]> {
     return this._wrapApiCall(this._apiName('selectOption'), async () => {
       return (await this._channel.selectOption({ selector, ...convertSelectOptionValues(values), ...options })).values;
     });
@@ -412,9 +408,7 @@ export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameIni
     await new Promise(fulfill => setTimeout(fulfill, timeout));
   }
 
-  async waitForFunction<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg, options?: WaitForFunctionOptions): Promise<SmartHandle<R>>;
-  async waitForFunction<R>(pageFunction: Func1<void, R>, arg?: any, options?: WaitForFunctionOptions): Promise<SmartHandle<R>>;
-  async waitForFunction<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg, options: WaitForFunctionOptions = {}): Promise<SmartHandle<R>> {
+  async waitForFunction<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg, options: WaitForFunctionOptions = {}): Promise<structs.SmartHandle<R>> {
     return this._wrapApiCall(this._apiName('waitForFunction'), async () => {
       if (typeof options.polling === 'string')
         assert(options.polling === 'raf', 'Unknown polling option: ' + options.polling);
@@ -425,7 +419,7 @@ export class Frame extends ChannelOwner<channels.FrameChannel, channels.FrameIni
         isFunction: typeof pageFunction === 'function',
         arg: serializeArgument(arg),
       });
-      return JSHandle.from(result.handle) as SmartHandle<R>;
+      return JSHandle.from(result.handle) as any as structs.SmartHandle<R>;
     });
   }
 
diff --git a/src/client/input.ts b/src/client/input.ts
index ef0a567415050..11ad5ba776141 100644
--- a/src/client/input.ts
+++ b/src/client/input.ts
@@ -16,8 +16,9 @@
  */
 
 import * as channels from '../protocol/channels';
+import * as api from '../../types/types';
 
-export class Keyboard {
+export class Keyboard implements api.Keyboard {
   private _channel: channels.PageChannel;
 
   constructor(channel: channels.PageChannel) {
@@ -45,7 +46,7 @@ export class Keyboard {
   }
 }
 
-export class Mouse {
+export class Mouse implements api.Mouse {
   private _channel: channels.PageChannel;
 
   constructor(channel: channels.PageChannel) {
@@ -73,7 +74,7 @@ export class Mouse {
   }
 }
 
-export class Touchscreen {
+export class Touchscreen implements api.Touchscreen {
   private _channel: channels.PageChannel;
 
   constructor(channel: channels.PageChannel) {
diff --git a/src/client/jsHandle.ts b/src/client/jsHandle.ts
index 55ff3e7c36013..5c2c410e909a0 100644
--- a/src/client/jsHandle.ts
+++ b/src/client/jsHandle.ts
@@ -15,27 +15,12 @@
  */
 
 import * as channels from '../protocol/channels';
-import { ElementHandle } from './elementHandle';
 import { ChannelOwner } from './channelOwner';
 import { parseSerializedValue, serializeValue } from '../protocol/serializers';
+import * as api from '../../types/types';
+import * as structs from '../../types/structs';
 
-type NoHandles<Arg> = Arg extends JSHandle ? never : (Arg extends object ? { [Key in keyof Arg]: NoHandles<Arg[Key]> } : Arg);
-type Unboxed<Arg> =
-  Arg extends ElementHandle<infer T> ? T :
-  Arg extends JSHandle<infer T> ? T :
-  Arg extends NoHandles<Arg> ? Arg :
-  Arg extends [infer A0] ? [Unboxed<A0>] :
-  Arg extends [infer A0, infer A1] ? [Unboxed<A0>, Unboxed<A1>] :
-  Arg extends [infer A0, infer A1, infer A2] ? [Unboxed<A0>, Unboxed<A1>, Unboxed<A2>] :
-  Arg extends Array<infer T> ? Array<Unboxed<T>> :
-  Arg extends object ? { [Key in keyof Arg]: Unboxed<Arg[Key]> } :
-  Arg;
-export type Func0<R> = string | (() => R | Promise<R>);
-export type Func1<Arg, R> = string | ((arg: Unboxed<Arg>) => R | Promise<R>);
-export type FuncOn<On, Arg2, R> = string | ((on: On, arg2: Unboxed<Arg2>) => R | Promise<R>);
-export type SmartHandle<T> = T extends Node ? ElementHandle<T> : JSHandle<T>;
-
-export class JSHandle<T = any> extends ChannelOwner<channels.JSHandleChannel, channels.JSHandleInitializer> {
+export class JSHandle<T = any> extends ChannelOwner<channels.JSHandleChannel, channels.JSHandleInitializer> implements api.JSHandle {
   private _preview: string;
 
   static from(handle: channels.JSHandleChannel): JSHandle {
@@ -48,18 +33,14 @@ export class JSHandle<T = any> extends ChannelOwner<channels.JSHandleChannel, ch
     this._channel.on('previewUpdated', ({preview}) => this._preview = preview);
   }
 
-  async evaluate<R, Arg>(pageFunction: FuncOn<T, Arg, R>, arg: Arg): Promise<R>;
-  async evaluate<R>(pageFunction: FuncOn<T, void, R>, arg?: any): Promise<R>;
-  async evaluate<R, Arg>(pageFunction: FuncOn<T, Arg, R>, arg: Arg): Promise<R> {
+  async evaluate<R, Arg>(pageFunction: structs.PageFunctionOn<T, Arg, R>, arg?: Arg): Promise<R> {
     const result = await this._channel.evaluateExpression({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
     return parseResult(result.value);
   }
 
-  async evaluateHandle<R, Arg>(pageFunction: FuncOn<T, Arg, R>, arg: Arg): Promise<SmartHandle<R>>;
-  async evaluateHandle<R>(pageFunction: FuncOn<T, void, R>, arg?: any): Promise<SmartHandle<R>>;
-  async evaluateHandle<R, Arg>(pageFunction: FuncOn<T, Arg, R>, arg: Arg): Promise<SmartHandle<R>> {
+  async evaluateHandle<R, Arg>(pageFunction: structs.PageFunctionOn<T, Arg, R>, arg?: Arg): Promise<structs.SmartHandle<R>> {
     const result = await this._channel.evaluateExpressionHandle({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
-    return JSHandle.from(result.handle) as SmartHandle<R>;
+    return JSHandle.from(result.handle) as any as structs.SmartHandle<R>;
   }
 
   async getProperty(propertyName: string): Promise<JSHandle> {
@@ -78,8 +59,8 @@ export class JSHandle<T = any> extends ChannelOwner<channels.JSHandleChannel, ch
     return parseResult((await this._channel.jsonValue()).value);
   }
 
-  asElement(): ElementHandle | null {
-    return null;
+  asElement(): T extends Node ? api.ElementHandle<T> : null {
+    return null as any;
   }
 
   async dispose() {
diff --git a/src/client/network.ts b/src/client/network.ts
index 91a97b8cf9a00..e9595b8e0cde9 100644
--- a/src/client/network.ts
+++ b/src/client/network.ts
@@ -26,6 +26,7 @@ import { isString, headersObjectToArray, headersArrayToObject } from '../utils/u
 import { Events } from './events';
 import { Page } from './page';
 import { Waiter } from './waiter';
+import * as api from '../../types/types';
 
 export type NetworkCookie = {
   name: string,
@@ -50,7 +51,7 @@ export type SetNetworkCookieParam = {
   sameSite?: 'Strict' | 'Lax' | 'None'
 };
 
-export class Request extends ChannelOwner<channels.RequestChannel, channels.RequestInitializer> {
+export class Request extends ChannelOwner<channels.RequestChannel, channels.RequestInitializer> implements api.Request {
   private _redirectedFrom: Request | null = null;
   private _redirectedTo: Request | null = null;
   _failureText: string | null = null;
@@ -167,7 +168,7 @@ export class Request extends ChannelOwner<channels.RequestChannel, channels.Requ
   }
 }
 
-export class Route extends ChannelOwner<channels.RouteChannel, channels.RouteInitializer> {
+export class Route extends ChannelOwner<channels.RouteChannel, channels.RouteInitializer> implements api.Route {
   static from(route: channels.RouteChannel): Route {
     return (route as any)._object;
   }
@@ -246,7 +247,7 @@ export type ResourceTiming = {
   responseEnd: number;
 };
 
-export class Response extends ChannelOwner<channels.ResponseChannel, channels.ResponseInitializer> {
+export class Response extends ChannelOwner<channels.ResponseChannel, channels.ResponseInitializer> implements api.Response {
   private _headers: Headers;
   private _request: Request;
 
@@ -316,7 +317,7 @@ export class Response extends ChannelOwner<channels.ResponseChannel, channels.Re
   }
 }
 
-export class WebSocket extends ChannelOwner<channels.WebSocketChannel, channels.WebSocketInitializer> {
+export class WebSocket extends ChannelOwner<channels.WebSocketChannel, channels.WebSocketInitializer> implements api.WebSocket {
   private _page: Page;
   private _isClosed: boolean;
 
diff --git a/src/client/page.ts b/src/client/page.ts
index 2a00a20698b71..894ca08c5e2b5 100644
--- a/src/client/page.ts
+++ b/src/client/page.ts
@@ -30,13 +30,14 @@ import { ElementHandle, determineScreenshotType } from './elementHandle';
 import { Worker } from './worker';
 import { Frame, verifyLoadState, WaitForNavigationOptions } from './frame';
 import { Keyboard, Mouse, Touchscreen } from './input';
-import { assertMaxArguments, Func1, FuncOn, SmartHandle, serializeArgument, parseResult, JSHandle } from './jsHandle';
+import { assertMaxArguments, serializeArgument, parseResult, JSHandle } from './jsHandle';
 import { Request, Response, Route, RouteHandler, WebSocket, validateHeaders } from './network';
 import { FileChooser } from './fileChooser';
 import { Buffer } from 'buffer';
 import { ChromiumCoverage } from './chromiumCoverage';
 import { Waiter } from './waiter';
-
+import * as api from '../../types/types';
+import * as structs from '../../types/structs';
 import * as fs from 'fs';
 import * as path from 'path';
 import * as util from 'util';
@@ -61,9 +62,8 @@ type PDFOptions = Omit<channels.PagePdfParams, 'width' | 'height' | 'margin'> &
   path?: string,
 };
 type Listener = (...args: any[]) => void;
-export type FunctionWithSource = (source: { context: BrowserContext, page: Page, frame: Frame }, ...args: any) => any;
 
-export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitializer> {
+export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitializer> implements api.Page {
   private _browserContext: BrowserContext;
   _ownedContext: BrowserContext | undefined;
 
@@ -79,9 +79,9 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
   readonly mouse: Mouse;
   readonly touchscreen: Touchscreen;
   coverage: ChromiumCoverage | null = null;
-  pdf?: (options?: PDFOptions) => Promise<Buffer>;
+  pdf: (options?: PDFOptions) => Promise<Buffer>;
 
-  readonly _bindings = new Map<string, FunctionWithSource>();
+  readonly _bindings = new Map<string, (source: structs.BindingSource, ...args: any[]) => any>();
   readonly _timeoutSettings: TimeoutSettings;
   _isPageCall = false;
   private _video: Video | null = null;
@@ -136,6 +136,8 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
     if (this._browserContext._browserName === 'chromium') {
       this.coverage = new ChromiumCoverage(this._channel);
       this.pdf = options => this._pdf(options);
+    } else {
+      this.pdf = undefined as any;
     }
   }
 
@@ -261,11 +263,13 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
     }
   }
 
-  async $(selector: string): Promise<ElementHandle<Element> | null> {
+  async $(selector: string): Promise<ElementHandle<SVGElement | HTMLElement> | null> {
     return this._attributeToPage(() => this._mainFrame.$(selector));
   }
 
-  async waitForSelector(selector: string, options?: channels.FrameWaitForSelectorOptions): Promise<ElementHandle<Element> | null> {
+  waitForSelector(selector: string, options: channels.FrameWaitForSelectorOptions & { state: 'attached' | 'visible' }): Promise<ElementHandle<SVGElement | HTMLElement>>;
+  waitForSelector(selector: string, options?: channels.FrameWaitForSelectorOptions): Promise<ElementHandle<SVGElement | HTMLElement> | null>;
+  async waitForSelector(selector: string, options?: channels.FrameWaitForSelectorOptions): Promise<ElementHandle<SVGElement | HTMLElement> | null> {
     return this._attributeToPage(() => this._mainFrame.waitForSelector(selector, options));
   }
 
@@ -273,28 +277,22 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
     return this._attributeToPage(() => this._mainFrame.dispatchEvent(selector, type, eventInit, options));
   }
 
-  async evaluateHandle<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<SmartHandle<R>>;
-  async evaluateHandle<R>(pageFunction: Func1<void, R>, arg?: any): Promise<SmartHandle<R>>;
-  async evaluateHandle<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<SmartHandle<R>> {
+  async evaluateHandle<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg): Promise<structs.SmartHandle<R>> {
     assertMaxArguments(arguments.length, 2);
     return this._attributeToPage(() => this._mainFrame.evaluateHandle(pageFunction, arg));
   }
 
-  async $eval<R, Arg>(selector: string, pageFunction: FuncOn<Element, Arg, R>, arg: Arg): Promise<R>;
-  async $eval<R>(selector: string, pageFunction: FuncOn<Element, void, R>, arg?: any): Promise<R>;
-  async $eval<R, Arg>(selector: string, pageFunction: FuncOn<Element, Arg, R>, arg: Arg): Promise<R> {
+  async $eval<R, Arg>(selector: string, pageFunction: structs.PageFunctionOn<Element, Arg, R>, arg?: Arg): Promise<R> {
     assertMaxArguments(arguments.length, 3);
     return this._attributeToPage(() => this._mainFrame.$eval(selector, pageFunction, arg));
   }
 
-  async $$eval<R, Arg>(selector: string, pageFunction: FuncOn<Element[], Arg, R>, arg: Arg): Promise<R>;
-  async $$eval<R>(selector: string, pageFunction: FuncOn<Element[], void, R>, arg?: any): Promise<R>;
-  async $$eval<R, Arg>(selector: string, pageFunction: FuncOn<Element[], Arg, R>, arg: Arg): Promise<R> {
+  async $$eval<R, Arg>(selector: string, pageFunction: structs.PageFunctionOn<Element[], Arg, R>, arg?: Arg): Promise<R> {
     assertMaxArguments(arguments.length, 3);
     return this._attributeToPage(() => this._mainFrame.$$eval(selector, pageFunction, arg));
   }
 
-  async $$(selector: string): Promise<ElementHandle<Element>[]> {
+  async $$(selector: string): Promise<ElementHandle<SVGElement | HTMLElement>[]> {
     return this._attributeToPage(() => this._mainFrame.$$(selector));
   }
 
@@ -309,12 +307,12 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
   async exposeFunction(name: string, playwrightFunction: Function) {
     return this._wrapApiCall('page.exposeFunction', async () => {
       await this._channel.exposeBinding({ name });
-      const binding: FunctionWithSource = (source, ...args) => playwrightFunction(...args);
+      const binding = (source: structs.BindingSource, ...args: any[]) => playwrightFunction(...args);
       this._bindings.set(name, binding);
     });
   }
 
-  async exposeBinding(name: string, playwrightBinding: FunctionWithSource, options: { handle?: boolean } = {}) {
+  async exposeBinding(name: string, playwrightBinding: (source: structs.BindingSource, ...args: any[]) => any, options: { handle?: boolean } = {}) {
     return this._wrapApiCall('page.exposeBinding', async () => {
       await this._channel.exposeBinding({ name, needsHandle: options.handle });
       this._bindings.set(name, playwrightBinding);
@@ -425,9 +423,7 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
     return this._viewportSize;
   }
 
-  async evaluate<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<R>;
-  async evaluate<R>(pageFunction: Func1<void, R>, arg?: any): Promise<R>;
-  async evaluate<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<R> {
+  async evaluate<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg): Promise<R> {
     assertMaxArguments(arguments.length, 2);
     return this._attributeToPage(() => this._mainFrame.evaluate(pageFunction, arg));
   }
@@ -538,7 +534,7 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
     return this._attributeToPage(() => this._mainFrame.hover(selector, options));
   }
 
-  async selectOption(selector: string, values: string | ElementHandle | SelectOption | string[] | ElementHandle[] | SelectOption[] | null, options?: SelectOptionOptions): Promise<string[]> {
+  async selectOption(selector: string, values: string | api.ElementHandle | SelectOption | string[] | api.ElementHandle[] | SelectOption[] | null, options?: SelectOptionOptions): Promise<string[]> {
     return this._attributeToPage(() => this._mainFrame.selectOption(selector, values, options));
   }
 
@@ -566,9 +562,7 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
     await this._mainFrame.waitForTimeout(timeout);
   }
 
-  async waitForFunction<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg, options?: WaitForFunctionOptions): Promise<SmartHandle<R>>;
-  async waitForFunction<R>(pageFunction: Func1<void, R>, arg?: any, options?: WaitForFunctionOptions): Promise<SmartHandle<R>>;
-  async waitForFunction<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg, options?: WaitForFunctionOptions): Promise<SmartHandle<R>> {
+  async waitForFunction<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg, options?: WaitForFunctionOptions): Promise<structs.SmartHandle<R>> {
     return this._attributeToPage(() => this._mainFrame.waitForFunction(pageFunction, arg, options));
   }
 
@@ -636,7 +630,7 @@ export class BindingCall extends ChannelOwner<channels.BindingCallChannel, chann
     super(parent, type, guid, initializer);
   }
 
-  async call(func: FunctionWithSource) {
+  async call(func: (source: structs.BindingSource, ...args: any[]) => any) {
     try {
       const frame = Frame.from(this._initializer.frame);
       const source = {
diff --git a/src/client/selectors.ts b/src/client/selectors.ts
index 9819f3ad6a442..65b5086fa119c 100644
--- a/src/client/selectors.ts
+++ b/src/client/selectors.ts
@@ -18,8 +18,9 @@ import { evaluationScript } from './clientHelper';
 import * as channels from '../protocol/channels';
 import { ChannelOwner } from './channelOwner';
 import { SelectorEngine } from './types';
+import * as api from '../../types/types';
 
-export class Selectors {
+export class Selectors implements api.Selectors {
   private _channels = new Set<SelectorsOwner>();
   private _registrations: channels.SelectorsRegisterParams[] = [];
 
diff --git a/src/client/video.ts b/src/client/video.ts
index f8358de3cf8c2..4ac2826b6ae39 100644
--- a/src/client/video.ts
+++ b/src/client/video.ts
@@ -16,8 +16,9 @@
 
 import * as path from 'path';
 import { Page } from './page';
+import * as api from '../../types/types';
 
-export class Video {
+export class Video implements api.Video {
   private _page: Page;
   private _pathCallback: ((path: string) => void) | undefined;
   private _pathPromise: Promise<string>;
diff --git a/src/client/webkitBrowser.ts b/src/client/webkitBrowser.ts
index 15a25a07afd1b..98a0d16f97b98 100644
--- a/src/client/webkitBrowser.ts
+++ b/src/client/webkitBrowser.ts
@@ -15,6 +15,7 @@
  */
 
 import { Browser } from './browser';
+import * as api from '../../types/types';
 
-export class WebKitBrowser extends Browser {
+export class WebKitBrowser extends Browser implements api.WebKitBrowser {
 }
diff --git a/src/client/worker.ts b/src/client/worker.ts
index cbd14378b6b08..0d5d12dff9942 100644
--- a/src/client/worker.ts
+++ b/src/client/worker.ts
@@ -17,12 +17,14 @@
 import { Events } from './events';
 import * as channels from '../protocol/channels';
 import { ChannelOwner } from './channelOwner';
-import { assertMaxArguments, Func1, JSHandle, parseResult, serializeArgument, SmartHandle } from './jsHandle';
+import { assertMaxArguments, JSHandle, parseResult, serializeArgument } from './jsHandle';
 import { Page } from './page';
 import { BrowserContext } from './browserContext';
 import { ChromiumBrowserContext } from './chromiumBrowserContext';
+import * as api from '../../types/types';
+import * as structs from '../../types/structs';
 
-export class Worker extends ChannelOwner<channels.WorkerChannel, channels.WorkerInitializer> {
+export class Worker extends ChannelOwner<channels.WorkerChannel, channels.WorkerInitializer> implements api.Worker {
   _page: Page | undefined;  // Set for web workers.
   _context: BrowserContext | undefined;  // Set for service workers.
 
@@ -45,19 +47,15 @@ export class Worker extends ChannelOwner<channels.WorkerChannel, channels.Worker
     return this._initializer.url;
   }
 
-  async evaluate<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<R>;
-  async evaluate<R>(pageFunction: Func1<void, R>, arg?: any): Promise<R>;
-  async evaluate<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<R> {
+  async evaluate<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg): Promise<R> {
     assertMaxArguments(arguments.length, 2);
     const result = await this._channel.evaluateExpression({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
     return parseResult(result.value);
   }
 
-  async evaluateHandle<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<SmartHandle<R>>;
-  async evaluateHandle<R>(pageFunction: Func1<void, R>, arg?: any): Promise<SmartHandle<R>>;
-  async evaluateHandle<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg): Promise<SmartHandle<R>> {
+  async evaluateHandle<R, Arg>(pageFunction: structs.PageFunction<Arg, R>, arg?: Arg): Promise<structs.SmartHandle<R>> {
     assertMaxArguments(arguments.length, 2);
     const result = await this._channel.evaluateExpressionHandle({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg) });
-    return JSHandle.from(result.handle) as SmartHandle<R>;
+    return JSHandle.from(result.handle) as any as structs.SmartHandle<R>;
   }
 }
diff --git a/types/structs.d.ts b/types/structs.d.ts
new file mode 100644
index 0000000000000..7d1e981d74601
--- /dev/null
+++ b/types/structs.d.ts
@@ -0,0 +1,45 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { JSHandle, ElementHandle, Frame, Page, BrowserContext } from './types';
+
+/**
+ * Can be converted to JSON
+ */
+export type Serializable = {};
+/**
+ * Can be converted to JSON, but may also contain JSHandles.
+ */
+export type EvaluationArgument = {};
+
+export type NoHandles<Arg> = Arg extends JSHandle ? never : (Arg extends object ? { [Key in keyof Arg]: NoHandles<Arg[Key]> } : Arg);
+export type Unboxed<Arg> =
+  Arg extends ElementHandle<infer T> ? T :
+  Arg extends JSHandle<infer T> ? T :
+  Arg extends NoHandles<Arg> ? Arg :
+  Arg extends [infer A0] ? [Unboxed<A0>] :
+  Arg extends [infer A0, infer A1] ? [Unboxed<A0>, Unboxed<A1>] :
+  Arg extends [infer A0, infer A1, infer A2] ? [Unboxed<A0>, Unboxed<A1>, Unboxed<A2>] :
+  Arg extends [infer A0, infer A1, infer A2, infer A3] ? [Unboxed<A0>, Unboxed<A1>, Unboxed<A2>, Unboxed<A3>] :
+  Arg extends Array<infer T> ? Array<Unboxed<T>> :
+  Arg extends object ? { [Key in keyof Arg]: Unboxed<Arg[Key]> } :
+  Arg;
+export type PageFunction0<R> = string | (() => R | Promise<R>);
+export type PageFunction<Arg, R> = string | ((arg: Unboxed<Arg>) => R | Promise<R>);
+export type PageFunctionOn<On, Arg2, R> = string | ((on: On, arg2: Unboxed<Arg2>) => R | Promise<R>);
+export type SmartHandle<T> = T extends Node ? ElementHandle<T> : JSHandle<T>;
+export type ElementHandleForTag<K extends keyof HTMLElementTagNameMap> = ElementHandle<HTMLElementTagNameMap[K]>;
+export type BindingSource = { context: BrowserContext, page: Page, frame: Frame };
diff --git a/types/types.d.ts b/types/types.d.ts
index d190f110ecaf9..5efd82e60e8b1 100644
--- a/types/types.d.ts
+++ b/types/types.d.ts
@@ -18,32 +18,7 @@ import { Protocol } from './protocol';
 import { ChildProcess } from 'child_process';
 import { EventEmitter } from 'events';
 import { Readable } from 'stream';
-
-/**
- * Can be converted to JSON
- */
-type Serializable = {};
-/**
- * Can be converted to JSON, but may also contain JSHandles.
- */
-type EvaluationArgument = {};
-
-type NoHandles<Arg> = Arg extends JSHandle ? never : (Arg extends object ? { [Key in keyof Arg]: NoHandles<Arg[Key]> } : Arg);
-type Unboxed<Arg> =
-  Arg extends ElementHandle<infer T> ? T :
-  Arg extends JSHandle<infer T> ? T :
-  Arg extends NoHandles<Arg> ? Arg :
-  Arg extends [infer A0] ? [Unboxed<A0>] :
-  Arg extends [infer A0, infer A1] ? [Unboxed<A0>, Unboxed<A1>] :
-  Arg extends [infer A0, infer A1, infer A2] ? [Unboxed<A0>, Unboxed<A1>, Unboxed<A2>] :
-  Arg extends [infer A0, infer A1, infer A2, infer A3] ? [Unboxed<A0>, Unboxed<A1>, Unboxed<A2>, Unboxed<A3>] :
-  Arg extends Array<infer T> ? Array<Unboxed<T>> :
-  Arg extends object ? { [Key in keyof Arg]: Unboxed<Arg[Key]> } :
-  Arg;
-type PageFunction<Arg, R> = string | ((arg: Unboxed<Arg>) => R | Promise<R>);
-type PageFunctionOn<On, Arg2, R> = string | ((on: On, arg2: Unboxed<Arg2>) => R | Promise<R>);
-type SmartHandle<T> = T extends Node ? ElementHandle<T> : JSHandle<T>;
-type ElementHandleForTag<K extends keyof HTMLElementTagNameMap> = ElementHandle<HTMLElementTagNameMap[K]>;
+import { Serializable, EvaluationArgument, PageFunction, PageFunctionOn, SmartHandle, ElementHandleForTag, BindingSource } from './structs';
 
 type PageWaitForSelectorOptionsNotHidden = PageWaitForSelectorOptions & {
   state: 'visible'|'attached';
@@ -52,8 +27,6 @@ type ElementHandleWaitForSelectorOptionsNotHidden = ElementHandleWaitForSelector
   state: 'visible'|'attached';
 };
 
-type BindingSource = { context: BrowserContext, page: Page, frame: Frame };
-
 /**
  * Page provides methods to interact with a single tab in a Browser, or an extension background page in Chromium. One Browser instance might have multiple Page instances.
  * This example creates a page, navigates it to a URL, and then saves a screenshot:
diff --git a/utils/doclint/check_public_api/index.js b/utils/doclint/check_public_api/index.js
index b1565d4891c86..2cd21039393db 100644
--- a/utils/doclint/check_public_api/index.js
+++ b/utils/doclint/check_public_api/index.js
@@ -200,7 +200,8 @@ function compareDocumentations(actual, expected) {
       [/Handle\<R\>/g, 'JSHandle'],
       [/JSHandle\<Object\>/g, 'JSHandle'],
       [/object/g, 'Object'],
-      [/Promise\<T\>/, 'Promise<Object>']
+      [/Promise\<T\>/, 'Promise<Object>'],
+      [/TextendsNode\?ElementHandle:null/, 'null|ElementHandle']
     ]
     let actualName = actual.name;
     for (const replacer of mdReplacers)
diff --git a/utils/generate_types/overrides.d.ts b/utils/generate_types/overrides.d.ts
index 07c03931bbf1e..38c4487877651 100644
--- a/utils/generate_types/overrides.d.ts
+++ b/utils/generate_types/overrides.d.ts
@@ -17,32 +17,7 @@ import { Protocol } from './protocol';
 import { ChildProcess } from 'child_process';
 import { EventEmitter } from 'events';
 import { Readable } from 'stream';
-
-/**
- * Can be converted to JSON
- */
-type Serializable = {};
-/**
- * Can be converted to JSON, but may also contain JSHandles.
- */
-type EvaluationArgument = {};
-
-type NoHandles<Arg> = Arg extends JSHandle ? never : (Arg extends object ? { [Key in keyof Arg]: NoHandles<Arg[Key]> } : Arg);
-type Unboxed<Arg> =
-  Arg extends ElementHandle<infer T> ? T :
-  Arg extends JSHandle<infer T> ? T :
-  Arg extends NoHandles<Arg> ? Arg :
-  Arg extends [infer A0] ? [Unboxed<A0>] :
-  Arg extends [infer A0, infer A1] ? [Unboxed<A0>, Unboxed<A1>] :
-  Arg extends [infer A0, infer A1, infer A2] ? [Unboxed<A0>, Unboxed<A1>, Unboxed<A2>] :
-  Arg extends [infer A0, infer A1, infer A2, infer A3] ? [Unboxed<A0>, Unboxed<A1>, Unboxed<A2>, Unboxed<A3>] :
-  Arg extends Array<infer T> ? Array<Unboxed<T>> :
-  Arg extends object ? { [Key in keyof Arg]: Unboxed<Arg[Key]> } :
-  Arg;
-type PageFunction<Arg, R> = string | ((arg: Unboxed<Arg>) => R | Promise<R>);
-type PageFunctionOn<On, Arg2, R> = string | ((on: On, arg2: Unboxed<Arg2>) => R | Promise<R>);
-type SmartHandle<T> = T extends Node ? ElementHandle<T> : JSHandle<T>;
-type ElementHandleForTag<K extends keyof HTMLElementTagNameMap> = ElementHandle<HTMLElementTagNameMap[K]>;
+import { Serializable, EvaluationArgument, PageFunction, PageFunctionOn, SmartHandle, ElementHandleForTag, BindingSource } from './structs';
 
 type PageWaitForSelectorOptionsNotHidden = PageWaitForSelectorOptions & {
   state: 'visible'|'attached';
@@ -51,8 +26,6 @@ type ElementHandleWaitForSelectorOptionsNotHidden = ElementHandleWaitForSelector
   state: 'visible'|'attached';
 };
 
-type BindingSource = { context: BrowserContext, page: Page, frame: Frame };
-
 export interface Page {
   evaluate<R, Arg>(pageFunction: PageFunction<Arg, R>, arg: Arg): Promise<R>;
   evaluate<R>(pageFunction: PageFunction<void, R>, arg?: any): Promise<R>;