playwright/docs/src/test-parallel.md

id	title
test-parallel	Parallelism and sharding

Playwright Test runs tests in parallel by default, using multiple worker processes.

Workers

Each worker process creates a new environment to run tests. By default, Playwright Test reuses the worker as much as it can to make testing faster.

However, test runner will create a new worker when retrying tests, after any test failure, to initialize a new environment, or just to speed up test execution if the worker limit is not reached.

You can control the maximum number of worker processes via command line or in the configuration file.

• Run in parallel by default

  npx playwright test
  

• Disable parallelization

  npx playwright test --worker 1
  

• Control the number of workers

  npx playwright test --worker 4
  

• In the configuration file

  // playwright.config.js
  module.exports = {
    // Limit the number of workers on CI, use default locally
    workers: process.env.CI ? 2 : undefined,
  };
  

  // playwright.config.ts
  import { PlaywrightTestConfig } from 'playwright/test';
  
  const config: PlaywrightTestConfig = {
    // Limit the number of workers on CI, use default locally
    workers: process.env.CI ? 2 : undefined,
  };
  export default config;
  

Each worker process is assigned a unique sequential index that is accessible through the workerInfo object.

Shards

Playwright Test can shard a test suite, so that it can be executed on multiple machines. For that, pass --shard=x/y to the command line. For example, to split the suite into three shards, each running one third of the tests:

npx playwright test --shard=1/3
npx playwright test --shard=2/3
npx playwright test --shard=3/3