Quote:Firefox users who run a recent Nightly version of the web browser may have stumbled upon a puzzling change that Mozilla implemented recently in the development version.

Firefox users who attempt to install a search provider from Mycroft Project, Mozilla AMO, or any other site that supports it, will notice that this is not possible anymore in the most recent Nightly version.

All you had to do previously was click on a search provider to get the "Add Search Engine" prompt to add it to the list of supported search engines.

Selection of a search provider link on a site like Mycroft Project does nothing anymore in Firefox Nightly (currently Firefox 65).

The sites use the method AddSearchProvider() for the functionality; the method is deprecated and support for it will be removed from Firefox.

Mozilla made the change in Firefox Nightly 65 already which is why users of Nightly can't add search providers anymore using sites and services that make use of the method. The organization did so to collect regressions and plans to disable the functionality in Firefox 66 Stable for all users.

Full reading: https://www.ghacks.net/2018/11/22/firefox-search-providers/