How is Playwright architected?

Playwright has three useful layers to reason about: the test process, the browser driver, and the browser itself. The test process runs your TypeScript and the runner. It communicates with a Playwright driver, which launches and controls the browser. Inside the browser, contexts provide isolation and pages provide navigation and DOM access.

The layers

• The Node process runs the test runner, fixtures, assertions and reporting
• The Playwright driver owns the browser lifecycle and the protocol connection
• A browser instance is an OS process or process group for Chromium, Firefox or WebKit
• A browser context is an isolated session with its own cookies, storage and cache
• A page is a tab inside a context, with its own DOM, network and JavaScript world

import { chromium } from "playwright";

const browser = await chromium.launch();
const context = await browser.newContext();
const page = await context.newPage();

await page.goto("https://example.com");
await context.close();
await browser.close();

Contexts are the isolation unit, not browser processes. Creating a context is cheap and does not require a new browser, so an entire test suite can reuse one browser per worker while every test still starts with clean storage. That is why a leaked cookie in one test does not normally affect the next.