Quote:Mozilla moved the remaining Firefox Test Pilot extensions for the Firefox web browser from the Test Pilot site to Mozilla AMO, the organization's official extensions website. The move marks the end of the Test Pilot program for Firefox.

The organization announced in January 2019 that it would shut down its Test Pilot program; Test Pilot was an experimental playground of sorts for upcoming Firefox features and extensions.

Mozilla used it to determine if certain features would be a good addition to Firefox or better suited if offered as standalone extensions. Several Test Pilot experiments, e.g. Tracking Protection or Page Shots, were integrated natively in the browser while others were offered as extensions or standalone projects.

The Firefox Test Pilot website displays a "good-bye" message when it is opened right now. Links to experiments, in fact, links to any subpage on the site, lead directly to the homepage.

Full reading: https://www.ghacks.net/2019/01/28/mozilla-moves-firefox-test-pilot-extensions-to-mozilla-amo/