Tests that have been merged on GitHub are mirrored at http://w3c-test.org/. On properly-configured systems, local files may also be served from the URL http://web-platform.test.

For running multiple tests inside a browser, there is a test runner located at /tools/runner/index.html.

This allows all the tests, or those matching a specific prefix (e.g. all tests under /dom/) to be run. For testharness.js tests, the results will be automatically collected, while the runner provides a simple UI for manually comparing reftest rendering and running manual tests.

Note, however, it does not currently handle more complex reftests with more than one reference involved.

Because it runs entirely in-browser, this runner cannot deal with edge-cases like tests that cause the browser to crash or hang.