WPT Test Certificates

The web-platform-tests project maintains a set of SSL certificates to allow contributors to execute tests requiring HTTPS locally.

Trusting Root CA

To prevent browser SSL warnings when running HTTPS tests locally, the web-platform-tests Root CA file cacert.pem in the tools/certs/ directory must be added as a trusted certificate in your OS/browser.

For Firefox, go to about:preferences and search for “certificates”.

For browsers that use the Certificate Authorities of the underlying OS, such as Chrome and Safari, you need to adjust the OS. For macOS, go to Keychain Access and add the certificate under login.

NOTE: The CA should not be installed in any browser profile used outside of tests, since it may be used to generate fake certificates. For browsers that use the OS certificate store, tests should therefore not be run manually outside a dedicated OS instance (e.g. a VM). To avoid this problem when running tests in Chrome or Firefox, use wpt run, which disables certificate checks and therefore doesn’t require the root CA to be trusted.

Regenerating certificates

The easiest way to regenerate the pregenerated certificates is to the the command

wpt regen-certs

By default this will not generate new certificates unless the existing ones are about to expire. In cases where the certificates need to be updated anyway (e.g. because the server configuration changed), this can be overridden with --force.

Generating the certificates requires OpenSSL to be installed.

Implementation Details

If you wish to manually generate new certificates for any reason, it’s possible to use OpenSSL when starting the server, or starting a test run, by providing the --ssl-type=openssl argument to the wpt serve or wpt run commands.

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"}}

Windows-specific Instructions

For Windows users, the easiest approach is likely to be using WSL and generate certificates in a Linux environment. However it is possible to install OpenSSL and generate the certificates without using WSL.

Shining Light provide a convenient installer that is known to work, but requires a little extra setup:

Run the installer for Win32_OpenSSL_v1.1.0b (30MB). During installation, change the default location for where to Copy OpenSSL Dlls from the System directory to the /bin directory.

After installation, ensure that the path to OpenSSL (typically, this will be C:\OpenSSL-Win32\bin) is in your %Path% Environment Variable. If you forget to do this part, you will most likely see a ‘File Not Found’ error when you start wptserve.

Finally, set the path value in the server configuration file to the default OpenSSL configuration file location. To do this, create a file called config.json. Then add the OpenSSL configuration below, ensuring that the key ssl/openssl/base_conf_path has a value that is the path to the OpenSSL config file (typically this will be C:\\OpenSSL-Win32\\bin\\openssl.cfg):

  "ssl": {
    "type": "openssl",
    "encrypt_after_connect": false,
    "openssl": {
      "openssl_binary": "openssl",
      "base_path: "_certs",
      "force_regenerate": false,
      "base_conf_path": "C:\\OpenSSL-Win32\\bin\\openssl.cfg"