• After following the installation instructions, you should not have a user.js file inside of your Profile Folder.
• The user.js file is a one-time thing, you only need it when installing the theme for the first time.
• Or if the theme were to add new options to the about:config page in an updated release (But that doesnt really happen often).

The user.js file is responsible for adding user-preferences/custom-settings into your Firefox Browser, in this case, the custom settings that you can change within FF Ultima; When Firefox starts up, it reads the user.js file (inside of the Profile Folder) and takes all of the preferences inside of it. So, if you leave the user.js file in the Profile Folder, every time you restart Firefox these settings will be read over and over again, resetting the settings inside.

Well, the list is long..

• Accessibility.

  • The ability to toggle almost all of the settings and styles on or off, one New Tab away.
  • Vertical Tabs optimization for browsing large amounts of tabs while using little screen real estate.
  • Downsizing the clutter shown with default Firefox (extension panel, url bar, compact spacing).
  • The ability to autohide/show the sidebars and vertical tabs saving even more screen real estate.
  • Cursor Pointers applied to certain buttons for ease of sight accessibility.
  • OS support for all.

• Modernity.

  • FF Ultima's main goal is to modernize the Firefox browser. While Firefox is pretty modern already, from an aesthetic standpoint.. it just misses the mark.
  • A simple touch like rounded corners, which can be disabled.
  • Or soft color palettes, less lines and borders.
  • Custom made icons that enhance and blend in.

• Color-Schemes.

  • It's not often that a CSS Theme gives the user more than one color-scheme for the browser. Users of FF Ultima can switch between a default dark mode or light mode just by changing their Computers color mode to dark or light.
  • If that isn't enough, Users can switch between color-schemes like Midnight, Catppuccin, Gruvbox, and more without visiting the add-on store.
  • If that isn't enough, Users can go to the add-on store and use their favorite Themes with FF Ultima.
  • If that isn't enough, Users can create their own color-schemes and integrate them right into the FF Ultima settings.

FF Ultima cycles between dark and light mode themes depending on your System's Current Color Mode.

• Windows > Settings > Personalize
• Mac > System Settings > Appearance
• Linux (Gnome) > Settings > Appearance
• Linux (KDE) > System Settings > Global Theme

If you change your dark/light color-scheme in the about:config page, the automatic theming will use those preferences.

• Unsupported. (planned for FF Ultima 2.0)