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Browser Types

Playwright supports three browser engines out of the box:

Chromium

Google Chrome and Microsoft Edge

Firefox

Mozilla Firefox

WebKit

Apple Safari

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Launching Browsers

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Basic Launch

const { chromium, firefox, webkit } = require('playwright');

// Launch Chromium
const browser = await chromium.launch();

// Launch Firefox
const browser = await firefox.launch();

// Launch WebKit
const browser = await webkit.launch();

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Launch Options

const browser = await chromium.launch({
  headless: false,           // Run in headed mode
  slowMo: 100,              // Slow down by 100ms
  devtools: true,           // Open DevTools
  args: ['--start-maximized'],  // Browser arguments
  executablePath: '/path/to/chrome'  // Custom browser binary
});
From server/browserType.ts:66, the launch() method validates options and manages the browser process lifecycle.

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Browser Class

The Browser class (client/browser.ts:31) represents a running browser instance: 
export class Browser extends ChannelOwner<channels.BrowserChannel> {
  readonly _contexts = new Set<BrowserContext>();
  private _isConnected = true;
  readonly _name: string;
  
  async newContext(options: BrowserContextOptions = {}): Promise<BrowserContext> {
    // Creates isolated browser context
  }
  
  async newPage(options: BrowserContextOptions = {}): Promise<Page> {
    // Shortcut: creates context + page
  }
  
  contexts(): BrowserContext[] {
    return [...this._contexts];
  }
  
  version(): string {
    return this._initializer.version;
  }
  
  async close(): Promise<void> {
    // Closes browser and all contexts
  }
}

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Browser Lifecycle

1

Launch

Browser process starts
const browser = await chromium.launch();
2

Create Contexts

Multiple isolated sessions
const context1 = await browser.newContext();
const context2 = await browser.newContext();
3

Use Browser

Perform automation tasks
4

Close

Clean up resources
await browser.close();

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Browser Connection State

// Check if browser is connected
if (browser.isConnected()) {
  console.log('Browser is running');
}

// Listen for disconnection
browser.on('disconnected', () => {
  console.log('Browser closed');
});
From client/browser.ts:147-194: 
isConnected(): boolean {
  return this._isConnected;
}

_didClose() {
  this._isConnected = false;
  this.emit(Events.Browser.Disconnected, this);
}

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Browser Properties

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Version Information

const version = browser.version();
console.log(`Browser version: ${version}`);

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Browser Type

const browserType = browser.browserType();
console.log(`Browser name: ${browserType.name()}`);

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Multiple Contexts Pattern

Browsers can host multiple independent contexts, which is much more efficient than launching multiple browsers: 
const browser = await chromium.launch();

// User 1 session
const context1 = await browser.newContext({
  viewport: { width: 1920, height: 1080 },
  userAgent: 'Custom User Agent 1'
});

// User 2 session (completely isolated)
const context2 = await browser.newContext({
  viewport: { width: 1280, height: 720 },
  userAgent: 'Custom User Agent 2'
});

// Contexts don't share cookies, storage, or cache
await Promise.all([
  context1.newPage().then(page => page.goto('https://example.com')),
  context2.newPage().then(page => page.goto('https://example.com'))
]);
Always close browsers to prevent resource leaks. Unclosed browsers continue running in the background.

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Persistent Context

Launch a browser with persistent storage (user data directory): 
const context = await chromium.launchPersistentContext('./user-data', {
  headless: false,
  viewport: { width: 1280, height: 720 }
});

// This context persists cookies, localStorage, etc.
const page = await context.newPage();
await page.goto('https://example.com');

// Login state is saved for next time
await context.close();
From server/browserType.ts:74: 
async launchPersistentContext(
  progress: Progress,
  userDataDir: string,
  options: BrowserTypeLaunchPersistentContextOptions
): Promise<BrowserContext>

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Remote Browser Connection

Connect to a browser running on another machine: 
const browser = await chromium.connect({
  wsEndpoint: 'ws://remote-server:3000'
});

// Use as normal
const context = await browser.newContext();
const page = await context.newPage();

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Browser Server

Start a browser server for remote connections: 
const browserServer = await chromium.launchServer({
  port: 3000
});

console.log(`Connect to: ${browserServer.wsEndpoint()}`);

// Remote clients can now connect
// ...

await browserServer.close();

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CDP Session (Chromium Only)

Access Chrome DevTools Protocol directly: 
const browser = await chromium.launch();

// Browser-level CDP session
const cdpSession = await browser.newBrowserCDPSession();

// Send CDP commands
await cdpSession.send('Performance.enable');
const metrics = await cdpSession.send('Performance.getMetrics');

await cdpSession.detach();
From client/browser.ts:151: 
async newBrowserCDPSession(): Promise<api.CDPSession> {
  return CDPSession.from((await this._channel.newBrowserCDPSession()).session);
}

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Error Handling

try {
  const browser = await chromium.launch({
    executablePath: '/invalid/path'
  });
} catch (error) {
  if (error.message.includes('Failed to launch')) {
    console.error('Browser failed to start');
  }
}

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Browser Process Management

Playwright automatically manages browser processes:
  1. Process Launch - Starts browser with appropriate flags
  2. Connection Setup - Establishes WebSocket or pipe communication
  3. Protocol Initialization - Sets up CDP/Juggler/Inspector protocol
  4. Context Management - Tracks all browser contexts
  5. Cleanup - Terminates browser process on close
From server/browserType.ts, the browser launch flow includes:
  • Option validation
  • Executable path resolution
  • Process spawning
  • Connection establishment
  • Protocol handshake

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Best Practices

Launch once, create multiple contexts. Contexts are lightweight.
// Good
const browser = await chromium.launch();
for (let i = 0; i < 10; i++) {
  const context = await browser.newContext();
  // ... test ...
  await context.close();
}
await browser.close();
Use try-finally or async disposal to ensure cleanup.
const browser = await chromium.launch();
try {
  // ... use browser ...
} finally {
  await browser.close();
}
Listen for disconnection events.
browser.on('disconnected', () => {
  console.log('Browser crashed or was closed');
});

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Browser Arguments

Customize browser behavior with command-line arguments: 
const browser = await chromium.launch({
  args: [
    '--disable-web-security',
    '--disable-features=IsolateOrigins,site-per-process',
    '--no-sandbox',
    '--disable-setuid-sandbox'
  ]
});
Disabling security features is dangerous. Only use in controlled test environments.

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Next Steps

Browser Contexts

Learn about isolated browser sessions

Pages and Frames

Working with tabs and iframes

Test Isolation

Ensuring test independence

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