Version: 1.9.0

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.

Playwright Inspector#

Playwright Inspector is a GUI tool that helps authoring and debugging Playwright scripts. That's our default recommended tool for scripts troubleshooting.

Playwright Inspector

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.

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#

  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
Chromium Developer Tools

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.

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)

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.
Highlight selectors

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.

Highlight selectors

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