playwright/docs/debug.md

<!-- THIS FILE IS NOW GENERATED -->

# 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.

<!-- GEN:toc -->
- [Run in headful mode](#run-in-headful-mode)
- [Visual Studio Code debugger](#visual-studio-code-debugger)
  * [Use launch config](#use-launch-config)
  * [Use the new JavaScript debugger](#use-the-new-javascript-debugger)
- [Browser Developer Tools](#browser-developer-tools)
  * [API for Chromium](#api-for-chromium)
- [Run in Debug Mode](#run-in-debug-mode)
  * [Defaults](#defaults)
  * [Debugging Selectors](#debugging-selectors)
  * [Evaluate Source Maps](#evaluate-source-maps)
- [Verbose API logs](#verbose-api-logs)
<!-- GEN:stop -->

## 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 `slowMo` option
to slow down execution and follow along while debugging.

```js
await chromium.launch({ headless: false, slowMo: 100 }); // or firefox, webkit
```

## Visual Studio Code debugger

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](https://code.visualstudio.com/docs/nodejs/nodejs-debugging)
for your Node.js project. Once configured launch the scripts with F5 and use
breakpoints.

### Use the new JavaScript debugger

VS Code 1.46+ introduces the new JavaScript debugger behind a feature flag. The
new debugger does not require a `launch.json` configuration. To use this:
1. Enable the preview debugger
   * Open JSON settings and add `"debug.javascript.usePreview": true`
   * Open settings UI and enable the `Debug › JavaScript: Use Preview`
     setting
1. Set a breakpoint in VS Code
   * Use the `debugger` keyword or set a breakpoint in the VS Code UI
1. 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](./verification.md#console-logs))
* Check **network activity** and other developer tools features

<a
href="https://user-images.githubusercontent.com/284612/77234134-5f21a500-6b69-11ea-92ec-1c146e1333ec.png"><img
src="https://user-images.githubusercontent.com/284612/77234134-5f21a500-6b69-11ea-92ec-1c146e1333ec.png"
width="500" alt="Chromium Developer Tools"></a>

> **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.

```js
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.

```sh
# Linux/macOS
$ PWDEBUG=1 npm run test

# Windows
$ set PWDEBUG=1
$ npm run test
```

### 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](./selectors.md). This can be used to verify text or
composite selectors. To use this:
1. Setup a breakpoint to pause the execution
1. Open the console panel in browser developer tools
1. 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.

<a
href="https://user-images.githubusercontent.com/284612/86857345-299abc00-c073-11ea-9e31-02923a9f0d4b.png"><img
src="https://user-images.githubusercontent.com/284612/86857345-299abc00-c073-11ea-9e31-02923a9f0d4b.png"
width="500" alt="Highlight selectors"></a>

### Evaluate Source Maps

PWDEBUG also enables source maps for
[`page.evaluate` executions](core-concepts.md#evaluation). This improves the
debugging experience for JavaScript executions in the page context.

<a
href="https://user-images.githubusercontent.com/284612/86857568-a6c63100-c073-11ea-82a4-bfd531a4ec87.png"><img
src="https://user-images.githubusercontent.com/284612/86857568-a6c63100-c073-11ea-82a4-bfd531a4ec87.png"
width="500" alt="Highlight selectors"></a>

## Verbose API logs

Playwright supports verbose logging with the `DEBUG` environment variable.

```sh
# Linux/macOS
$ DEBUG=pw:api npm run test

# Windows
$ set DEBUG=pw:api
$ npm run test
```

[Playwright]: api.md#class-playwright "Playwright"
[Browser]: api.md#class-browser "Browser"
[BrowserContext]: api.md#class-browsercontext "BrowserContext"
[Page]: api.md#class-page "Page"
[Frame]: api.md#class-frame "Frame"
[ElementHandle]: api.md#class-elementhandle "ElementHandle"
[JSHandle]: api.md#class-jshandle "JSHandle"
[ConsoleMessage]: api.md#class-consolemessage "ConsoleMessage"
[Dialog]: api.md#class-dialog "Dialog"
[Download]: api.md#class-download "Download"
[Video]: api.md#class-video "Video"
[FileChooser]: api.md#class-filechooser "FileChooser"
[Keyboard]: api.md#class-keyboard "Keyboard"
[Mouse]: api.md#class-mouse "Mouse"
[Touchscreen]: api.md#class-touchscreen "Touchscreen"
[Request]: api.md#class-request "Request"
[Response]: api.md#class-response "Response"
[Selectors]: api.md#class-selectors "Selectors"
[Route]: api.md#class-route "Route"
[WebSocket]: api.md#class-websocket "WebSocket"
[TimeoutError]: api.md#class-timeouterror "TimeoutError"
[Accessibility]: api.md#class-accessibility "Accessibility"
[Worker]: api.md#class-worker "Worker"
[BrowserServer]: api.md#class-browserserver "BrowserServer"
[BrowserType]: api.md#class-browsertype "BrowserType"
[Logger]: api.md#class-logger "Logger"
[ChromiumBrowser]: api.md#class-chromiumbrowser "ChromiumBrowser"
[ChromiumBrowserContext]: api.md#class-chromiumbrowsercontext "ChromiumBrowserContext"
[ChromiumCoverage]: api.md#class-chromiumcoverage "ChromiumCoverage"
[CDPSession]: api.md#class-cdpsession "CDPSession"
[FirefoxBrowser]: api.md#class-firefoxbrowser "FirefoxBrowser"
[WebKitBrowser]: api.md#class-webkitbrowser "WebKitBrowser"
[Array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array "Array"
[Buffer]: https://nodejs.org/api/buffer.html#buffer_class_buffer "Buffer"
[ChildProcess]: https://nodejs.org/api/child_process.html "ChildProcess"
[Element]: https://developer.mozilla.org/en-US/docs/Web/API/element "Element"
[Error]: https://nodejs.org/api/errors.html#errors_class_error "Error"
[EvaluationArgument]: #evaluationargument "Evaluation Argument"
[Map]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map "Map"
[Object]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object "Object"
[Promise]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise "Promise"
[RegExp]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp "RegExp"
[Serializable]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#Description "Serializable"
[UIEvent.detail]: https://developer.mozilla.org/en-US/docs/Web/API/UIEvent/detail "UIEvent.detail"
[URL]: https://nodejs.org/api/url.html "URL"
[USKeyboardLayout]: ../src/usKeyboardLayout.ts "USKeyboardLayout"
[UnixTime]: https://en.wikipedia.org/wiki/Unix_time "Unix Time"
[boolean]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type "Boolean"
[function]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function "Function"
[iterator]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols "Iterator"
[null]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/null "null"
[number]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type "Number"
[origin]: https://developer.mozilla.org/en-US/docs/Glossary/Origin "Origin"
[selector]: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors "selector"
[Readable]: https://nodejs.org/api/stream.html#stream_class_stream_readable "Readable"
[string]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type "string"
[xpath]: https://developer.mozilla.org/en-US/docs/Web/XPath "xpath"