A BrowserContext is an isolated browser session inside one browser process, with its own cookies, local storage and cache. Creating one is fast, so a single test can play several users at once, for example two people in the same chat:

import { test, expect } from '@playwright/test';

test('a message reaches the other user', async ({ browser }) => {
  const aliceContext = await browser.newContext({ storageState: 'playwright/.auth/alice.json' });
  const bobContext = await browser.newContext({ storageState: 'playwright/.auth/bob.json' });

  try {
    const alice = await aliceContext.newPage();
    const bob = await bobContext.newPage();
    await alice.goto('/chat');
    await bob.goto('/chat');

    await alice.getByRole('textbox', { name: 'Message' }).fill('Hi Bob');
    await alice.getByRole('button', { name: 'Send' }).click();

    await expect(bob.getByText('Hi Bob')).toBeVisible();
  } finally {
    await aliceContext.close();
    await bobContext.close();
  }
});

The relative goto('/chat') works because contexts created with browser.newContext() inside Playwright Test pick up baseURL from the config. Each context starts from its own saved sign-in state, and closing the contexts at the end frees their resources. The page fixture already gives each test its own context, so you only create extra ones when a test needs more than one user.

Sources: Playwright browser contexts, Playwright use options, Playwright authentication