userChrome.css theme for Firefox Developer Edition.
Clone or download
Type Name Latest commit message Commit time
Failed to load latest commit information. Note about dark theme Apr 9, 2018
userChrome-safaristyle.css Fix address bar focus layout Apr 9, 2018
userChrome.css Smaller arrows when browser width is narrower Nov 14, 2017

Minimalistic Firefox userChrome.css tweak/theme for OS X

CustomCSSforFX has a good tutorial on how to tweak Firefox with pure CSS only. This is my "theme" for Firefox Developer Edition. By enabling, you will be able to get Firefox to look like this:

Tested: Firefox Quantum: Developer Edition, Firefox 58.0b1 (64-bit)


  1. Go to Library/Application Support/Firefox, find your profile folder and create folder "chrome" (lowercase) under it
  2. Create userChrome.css file to that folder and paste contents of userChrome.css or userChrome-safaristyle.css if you prefer Safari UI
  3. Restart Firefox
  4. Note: If you use dark theme or FirefoxDeveloperEdition, you should change the base theme to Light first (Tools > Add-ons > Themes).

More tweaking tips in CustomCSSforFX repository.

Screenshot Screenshot of Safari styled Firefox 58.