Mozilla is working on a new mobile browser for Google’s Android operating system. Called Firefox Preview currently, it is available as a preview version right now. As is the case with desktop Firefox, Firefox Preview for Android is available in different editions that differ in terms of stability and development progress.
Firefox Preview Stable is the main version that is comparable to Firefox Stable for desktop operating systems. There is also Firefox Preview Beta and Firefox Preview Nightly for Developers.
While there are not many major differences in regards to core functionality between the different editions usually, it appears that Mozilla decided to implement one in Firefox Preview that might irritate some users of Stable or Beta versions of the browser.
Firefox supported the internal about:config page for a long time; it provides an interface to make advanced configuration changes directly in the web browser. Firefox for the desktop and mobile supported it until now.
When you try to load about:config in Firefox Preview Stable or Firefox Preview Beta, you are greeted with a “cannot complete request” message instead.
The page states that “additional information about this problem or error is currently unavailable”, and there is a “try again” button to retry loading the page.
It is unclear at this point if the change is deliberate or if Mozilla plans to unblock the page before final release. As it stands, Firefox Preview Stable and Beta users cannot make use of about:config to make changes to Firefox’s configuration.
If you compare that to the current Firefox mobile browser for Android, which supports about:config, you have to wonder whether that is an intentional change or something that just has not been implemented yet.
It seems expected behavior judging from the post of a contributor on the official GitHub project website:
This is expected behavior from GeckoView. Fenix does not control access to it. When Fenix nightly is released it will have access to about:config for users that have that requirement.
Closing Words
It is probably not a good idea to release Firefox Stable or Beta versions for Android without support for about:config as users who used it in the past will certainly be disappointed that the feature is not available. It is also difficult to justify considering that the previous Firefox for Android supported it and desktop Firefox Stable supports it as well.