How to - Atavic/legacy-user.js Wiki
You can customize Mozilla-based products as Firefox or Palemoon using the UI Menu: select Edit -> Preferences
More options are available by typing
about:config. All the changes you make are in bold fonts in the config screen. By double-clicking on a preference entry you reset it to the default value.
With Legacy-user.js file you apply modifications by putting the custom user.js file in the profile folder. Place the modified user.js file in one of the following folders (note that
<profile folder> and
<username> change in your setup):
For Android also see: https://github.com/pyllyukko/user.js/issues/14
The .mozilla folder is hidden by default.
Mac (may be in one of the following locations):
~/Library/Application Support/Firefox/Profiles/<profile folder> ~/Library/Mozilla/Firefox/Profiles/<profile folder>
The tilde (~) refers to logged user's Home folder.
Legacy-user.js is then read when the browser starts. Every preference in the file will be written to the prefs.js file. Note that removing a setting from user.js will NOT remove it from prefs.js. You need to change the setting in the UI, the
about:config editor or edit the prefs.js file.