Please Mozilla, don't touch the user.js functionality in Firefox

[harlan4096]

A bug report opened about nine months ago on Mozilla's Bugzilla bug tracking site for Firefox suggests that the organization could disable reading the user.js file of the Firefox browser by default in the future.

If you have not heard about user.js before, it is a configuration file that controls preferences in the Firefox web browser. One of the main advantages over Firefox's preferences file is that it has priority and that it is a user-owned file that is left untouched when Mozilla makes changes to the browser.

I suggest you check out the ghacks user.js repository on Github for detailed information and an extensive file to improve privacy and security of the Firefox web browser.

The bug reporter states in the description that he "never fully understood the point of having this file", that people have abused it and "broke stuff" in Firefox, and that it offers nothing that cannot be achieved by modifying the default preferences file, or by using Enterprise policies. Additionally, since Firefox needs to check for the file's existence regardless of whether it exists or not, it is causing "additional IO early on startup".

According to telemetry that Mozilla gathered, about 3% of Firefox installations that report telemetry use user.js files.

Others have pointed out early in the discussion that there are advantages, including maintaining Firefox preferences over multiple systems, when reinstalling Firefox, moving it, or installing a new version or edition of the browser. Another benefit that was pointed out early in the discussion is that user.js preferences are permanent (unless edited by the user) whereas prefs.js preferences are not as they may be modified by Mozilla at any time.

As Mike Kaply puts it, "he advantage here is that you can have a file that you keep around and just drop into a profile directory and Firefox doesn't mess with it".

The suggestion brought forward is to disable user.js by default but introduce a preference in Firefox that users need to enable actively so that the user.js file is read again.
...

Continue Reading