Implementation:Microsoft Playwright CrConnection

Knowledge Sources	Microsoft_Playwright
Domains	Chromium, CDP
Last Updated	2026-02-12 00:00 GMT

Overview

Concrete tool for managing the Chrome DevTools Protocol (CDP) connection and session multiplexing provided by the Playwright library.

Description

The `CRConnection` class extends `SdkObject` and manages the raw CDP transport to a Chromium browser. It maintains a `rootSession` for browser-level commands and a map of `CRSession` instances keyed by session ID for target-specific communication. `CRSession` handles sending typed CDP commands, receiving responses via callbacks, and dispatching events. The connection manages session creation/disposal, message routing, protocol logging, and disconnect handling. A special `kBrowserCloseMessageId` is used for the browser close command. Both classes emit events via Node.js `EventEmitter`.

Usage

Use CrConnection when Playwright communicates with Chromium-based browsers over the Chrome DevTools Protocol, managing multiple targets (pages, service workers, etc.) through session multiplexing.

Code Reference

Source Location

• Repository: Microsoft_Playwright
• File: packages/playwright-core/src/server/chromium/crConnection.ts

Signature

export const kBrowserCloseMessageId = -9999;

export class CRConnection extends SdkObject {
  readonly rootSession: CRSession;
  readonly _sessions: Map<string, CRSession>;
  constructor(parent: SdkObject, transport: ConnectionTransport, protocolLogger: ProtocolLogger, browserLogsCollector: RecentLogsCollector);
}

export class CRSession extends SdkObject {
  readonly sessionId: string;
  async send<T extends keyof Protocol.CommandParameters>(method: T, params?: Protocol.CommandParameters[T]): Promise<Protocol.CommandReturnValues[T]>;
}

Import

import { CRConnection, CRSession, kBrowserCloseMessageId } from '../server/chromium/crConnection';

I/O Contract

Inputs

Name	Type	Required	Description
parent	SdkObject	Yes	Parent SDK object
transport	ConnectionTransport	Yes	The underlying message transport (WebSocket or pipe)
protocolLogger	ProtocolLogger	Yes	Logger for CDP message tracing
browserLogsCollector	RecentLogsCollector	Yes	Collector for browser stderr logs

Outputs

Name	Type	Description
rootSession	CRSession	The browser-level CDP session
response	Protocol.CommandReturnValues[T]	Typed response from a CDP command

Usage Examples

import { CRConnection } from '../server/chromium/crConnection';

const connection = new CRConnection(parentSdkObject, transport, logger, logsCollector);
const version = await connection.rootSession.send('Browser.getVersion');
console.log('Browser version:', version.product);

Related Pages

• Environment:Microsoft_Playwright_Node_Runtime_Environment