Similar to about: flags in Chrome, Mozilla may soon allow users to try out Firefox new features it is working on by visiting the ‘Firefox Experiments’ section in the about: preferences page.
Rather than visiting about config and enabling a feature that is currently under development, Mozilla through ‘Feature Gates’ system to expose some features for testing in browser settings, users can turn on the desired features that are intended for developers.
The experiments section in Nightly at ‘about:preferences#experimental’ is not available by default, you can enable and turn on features such as AVIF, CSS Masonry Layout, and WebGPU, for that
Enable Firefox’s experimental features in Nightly
1. Open Firefox browser
2. Visit about:config
3. Search for “experimental”, toggle browser.
browser.preferences.experimental
Click on menu > Options or visit about: preferences to notice “Nightly Experiments” with new features to play.
Since some of these experiments can break Firefox when enabled, that’s why these features won’t be turned on when Firefox restores the browser from a crash and are disabled when you run Firefox in Safe Mode.
Mozilla warns ‘changing advanced configuration preferences’ may affect Firefox performance or security, so proceed with caution.
Related articles:
Mozilla adds Experimental Support for AV1 Image File Format (AVIF) to Firefox 77
Mozilla Firefox to Run Experiments to Curb Notification Spam
Firefox Test Pilot Experiments available on addons.Mozilla.org for download
Telemetry in Firefox may install and run experiments from time to time
How to Remove ‘Experiments’ Panel from Add-ons Manager in Firefox?