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web-platform-tests/wpt

★ 5,926HTMLAudience · developerComplexity · 3/5Setup · moderate

TLDR

WPT is the shared test suite all major browsers use to verify they behave the same way on web features, if you find a browser inconsistency you can add a single test and every browser team will see it.

Mindmap

mindmap
  root((wpt))
    What It Does
      Test browser behavior
      Catch inconsistencies
      Track browser progress
    Test Coverage
      HTML standards
      JavaScript behavior
      Web APIs
    Tools
      wpt CLI tool
      Local test server
      wpt.fyi results site
    Contribution
      Add single test
      Fork and pull request
      Linter validation
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Code map

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Things people build with this

USE CASE 1

Run the WPT suite locally against a browser build to check which web standards it supports correctly before shipping.

USE CASE 2

Add a test that reproduces a browser inconsistency you found so Chrome, Firefox, and Safari teams can all track and fix it.

USE CASE 3

Check wpt.fyi to compare how major browsers perform on any specific web feature without running tests yourself.

Tech stack

HTMLJavaScript

Getting it running

Difficulty · moderate Time to first run · 30min

Requires a local browser binary and the wpt CLI, full setup guide is at web-platform-tests.org.

In plain English

Web-platform-tests, often called WPT, is a shared collection of tests for web browsers. The goal is to check whether browsers like Chrome, Firefox, and Safari all behave the same way when running the same web features. When browsers disagree on how something should work, websites break in unpredictable ways depending on which browser a visitor uses. This project exists so browser makers can run a common test suite and catch those disagreements before shipping new versions. The tests cover a wide range of web standards, including HTML, JavaScript behavior in the browser, and the structure of web pages. They are written by contributors from browser teams, standards bodies, and independent developers. Anyone can add a test, and the project explicitly welcomes small contributions, such as a single test that reproduces a bug you noticed. You can see the results of these tests run across multiple browsers at wpt.fyi, which keeps an ongoing archive of how each browser performs. A live version of the test suite is also publicly available at wpt.live, so you can run tests against any browser just by visiting the site. For developers who want to run the tests locally, the project includes a command-line tool called wpt that handles starting a local server, running tests against a specific browser, and validating that test files follow the project's conventions. The documentation site at web-platform-tests.org explains how to get set up. Contributing follows standard open-source practice: fork the repository, create a branch, make changes, run the linter, and open a pull request. There is also a real-time chat channel and a mailing list for questions and discussion.

Copy-paste prompts

Prompt 1
Using the wpt command-line tool, how do I run the CSS Grid layout tests locally against Chrome and see which ones fail?
Prompt 2
Show me how to write a minimal WPT test that checks whether two browsers handle a specific JavaScript API the same way.
Prompt 3
How do I set up the WPT local server and run a subset of HTML tests against Firefox to generate a results report?
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