Debugging tools

Playwright scripts work with existing debugging tools, like Node.js debuggers and browser developer tools. Playwright also introduces new debugging features for browser automation.

• Run in headful mode
• Visual Studio Code debugger (Node.JS)
• Browser Developer Tools
• Run in Debug Mode
• Verbose API logs

Run in headful mode

Playwright runs browsers in headless mode by default. To change this behavior, use headless: false as a launch option. You can also use the slow_mo option to slow down execution and follow along while debugging.

Sync

chromium.launch(headless=False, slow_mo=100) # or firefox, webkit

Async

await chromium.launch(headless=False, slow_mo=100) # or firefox, webkit

Visual Studio Code debugger (Node.JS)

The VS Code debugger can be used to pause and resume execution of Playwright scripts with breakpoints. The debugger can be configured in two ways.

Use launch config

Setup launch.json configuration for your Node.js project. Once configured launch the scripts with F5 and use breakpoints.

Use the new JavaScript debugging terminal

VS Code 1.46+ introduced the new JavaScript debugger that does not require a launch.json configuration. To use it:

1. Set a breakpoint in VS Code
   • Use the debugger keyword or set a breakpoint in the VS Code UI
2. Run your Node.js script from the terminal

Browser Developer Tools

You can use browser developer tools in Chromium, Firefox and WebKit while running a Playwright script. Developer tools help to:

• Inspect the DOM tree and find element selectors
• See console logs during execution (or learn how to read logs via API)
• Check network activity and other developer tools features

For WebKit: Note that launching WebKit Inspector during the execution will prevent the Playwright script from executing any further.

API for Chromium

In Chromium, you can also open developer tools through a launch option.

Sync

chromium.launch(devtools=True)

Async

await chromium.launch(devtools=True)

Run in Debug Mode

Set the PWDEBUG environment variable to run your scripts in debug mode. This configures the browser for debugging.

# Linux/macOS

$ PWDEBUG=1 pytest -s

# Windows

$ set PWDEBUG=1

$ pytest -s

Defaults

With PWDEBUG, the following defaults are configured for you:

• Run in headful: With PWDEBUG, browsers always launch in headful mode
• Disables timeout: PWDEBUG sets timeout to 0 (= no timeout)
• Preserve DevTools preferences: When used with devtools: true, PWDEBUG preserves the docked/undocked state of Chrome DevTools

Debugging Selectors

PWDEBUG configures a playwright object in the browser to highlight Playwright selectors. This can be used to verify text or composite selectors. To use this:

1. Setup a breakpoint to pause the execution
2. Open the console panel in browser developer tools
3. Use the playwright API
   • playwright.$(selector): Highlight the first occurrence of the selector. This reflects how page.$ would see the page.
   • playwright.$$(selector): Highlight all occurrences of the selector. This reflects how page.$$ would see the page.
   • playwright.inspect(selector): Inspect the selector in the Elements panel.
   • playwright.clear(): Clear existing highlights.

Evaluate Source Maps

PWDEBUG also enables source maps for page.evaluate(expression, **kwargs) executions. This improves the debugging experience for JavaScript executions in the page context.

Verbose API logs

Playwright supports verbose logging with the DEBUG environment variable.

# Linux/macOS

$ DEBUG=pw:api pytest -s

# Windows

$ set DEBUG=pw:api

$ pytest -s