Web-platform-tests are designed to run in a self-contained environment on the local computer. All the required resources are packaged with the web-platform-tests repository.


Hosts configuration

The tests depend on certain domains being available. These are typically configured locally with web-platform.test as the top level domain and five subdomains. To configure these domains you need to edit your hosts file. The following entries are required:	web-platform.test	www.web-platform.test	www1.web-platform.test	www2.web-platform.test	xn--n8j6ds53lwwkrqhv28a.web-platform.test	xn--lve-6lad.web-platform.test

Cloning the Repository

If you have not done so, clone the web-platform-tests repository:

git clone --recursive git@github.com:w3c/web-platform-tests.git

If you have already made a clone, but did not specify --recursive update all submodules:

git submodule update --init --recursive

Font Files

Many layout tests require a set of test-specific fonts, notably Ahem. These are available from the CSS Fonts website. These must be installed according to the normal font-install procedure for your operating system.

Running the Test Server

The test environment can be started using


This will start HTTP servers on two ports and a websockets server on one port. By default one web server starts on port 8000 and the other ports are randomly-chosen free ports. Tests must be loaded from the first HTTP server in the output. To change the ports, copy the config.default.json file to config.json and edit the new file, replacing the part that reads:

"http": [8000, "auto"]

to some port of your choice e.g.

"http": [1234, "auto"]

If you installed OpenSSL in such a way that running openssl at a command line doesn't work, you also need to adjust the path to the OpenSSL binary. This can be done by adding a section to config.json like:

"ssl": {"openssl": {"binary": "/path/to/openssl"}}