How BrowserContext Isolation Solves State Pollution in Concurrent Playwright Tests

When running highly concurrent end-to-end tests with Playwright, shared browser state can silently corrupt test results — a problem known as state pollution. The recommended fix is to create a fresh BrowserContext for each test, which provides an isolated session with separate cookies and local storage, similar to an incognito window. Lifecycle hooks like test.beforeEach and test.afterEach ensure that each context is properly set up before a test runs and torn down immediately after. Backend data cleanup is also critical and can be handled in afterEach by making targeted API calls — such as DELETE requests — using Playwright's built-in request context. This approach is more efficient than launching a new browser instance per test, since it reuses a single browser process while still guaranteeing full isolation.