Implementation:Microsoft Playwright Client Connection

Knowledge Sources	Microsoft_Playwright
Domains	Client-Server Communication, RPC Protocol
Last Updated	2026-02-12 00:00 GMT

Overview

Concrete tool for managing the client-to-server RPC connection provided by the Playwright library.

Description

The `Connection` class is the central hub of Playwright's client-side communication layer. It extends `EventEmitter` and manages the bidirectional message passing between the client and server processes. The class maintains a registry of all `ChannelOwner` objects (stored in `_objects` map), dispatches method calls to the server with callback tracking, and processes incoming messages that create, update, or dispose remote objects. It also handles protocol validation, error deserialization, and tracing state management. The inner `Root` class serves as the root of the object hierarchy and bootstraps the connection by initializing the `Playwright` instance.

Usage

Use this class to establish and manage the connection between a Playwright client and the Playwright server process. It is the entry point for all client-side RPC communication.

Code Reference

Source Location

• Repository: Microsoft_Playwright
• File: packages/playwright-core/src/client/connection.ts

Signature

export class Connection extends EventEmitter {
  readonly _objects: Map<string, ChannelOwner>;
  onmessage: (message: object) => void;
  readonly _instrumentation: ClientInstrumentation;
  readonly headers: HeadersArray;

  constructor(platform: Platform, localUtils?: LocalUtils, instrumentation?: ClientInstrumentation, headers?: HeadersArray);
  markAsRemote(): void;
  isRemote(): boolean;
  useRawBuffers(): void;
  rawBuffers(): boolean;
  localUtils(): LocalUtils | undefined;
}

Import

import { Connection } from './client/connection';

I/O Contract

Inputs

Name	Type	Required	Description
platform	Platform	Yes	Platform abstraction for environment-specific operations
localUtils	LocalUtils	No	Local utility functions reference
instrumentation	ClientInstrumentation	No	Client instrumentation for tracing/debugging
headers	HeadersArray	No	HTTP headers to include with connection requests

Outputs

Name	Type	Description
_objects	Map<string, ChannelOwner>	Registry of all remote objects keyed by GUID
Playwright	Playwright	The initialized Playwright instance (via Root.initialize)

Usage Examples

import { Connection } from 'playwright-core/lib/client/connection';

const connection = new Connection(platform, localUtils);
connection.onmessage = (message) => transport.send(message);
transport.onmessage = (message) => connection.dispatch(message);

const playwright = await connection.initializePlaywright();

Related Pages

• Environment:Microsoft_Playwright_Node_Runtime_Environment