Origin Trials

Mozilla Firefox Origin Trials are a way for websites to opt-in to experimental web platform features.

Current Trials

Currently active trials are:

• MLS (Messaging Layer Security): Enables the `window.MLS` experimental API.

• COEP: credentialless: Enables the `credentialless` value for the `Cross-Origin-Embedder-Policy` header.
  • COEP: credentialless is enabled in Firefox Desktop by default since Firefox 119, you only need to request an origin trial if you need it for Firefox Android.

• Privacy Preserving Attribution: See intent to experiment.

Requesting a trial for your website

In order to request a trial please click here:

• Origin trial request.

That will take you to Bugzilla with an already-prefilled template where you'd need to fill a few details (like trial name, website origin, whether subdomains should be included, and a suggested expiration date / other details if you know them). A token will be given to you in that bug.

Using the trial token

Once you get a reply with a token, you can use them by serving your page with the relevant header:

origin-trial: your-token

Or with a meta tag:

<meta http-equiv="origin-trial" content="your-token">

Articles

Articles and blog posts about Origin Trials in general:

• 2020-10-28 Stephanie Stimac: What the heck is an Origin Trial?

  Origin Trials are a way for developers to test and use experimental web platform features for a limited amount of time in exchange for feedback. Feedback is key in origin trials as browsers are granting developers access to ensure that the feature makes sense and is usable.

• ...

Other Browsers Origin Trials

Documentation and lists of origin trials in other browsers:

• Google Chrome Origin Trials
  • Chrome Origin Trials Motivation and Explainer
  • Origin Trials Guide for Web Developers
  • Chrome Experimental Features: Origin Trials
• Microsoft Edge Origin Trials
  • Microsoft Edge Origin Trials Guide
  • 2023-10-26 Use Origin Trials in Microsoft Edge