MartinFox is a simple userChrome.css for Firefox 89.

The goal is to have the absolute minimum in there. Honestly I don't really care how Firefox looks: I usually use the standard for a lot of stuff. But this "Photon" thing ... yeah nah. I can live with some extra spacing or whatnot, but it's just impossible to see which tab is active. I don't know how anyone could possibly think this was a good idea.

A lot of the CSS I found is a complete restyling of Firefox, often with thousands of lines of CSS. Nice, but that's a bit too much for me. This is just 61 lines.

There's a bunch of other stuff in there as well, it's just a copy of what I like to put in there. The CSS file is fairly well annotated, so you can add/remove/modify stuff according to preferences. It should hopefully be fairly future-compatible too on account being fairly small.

Screenshot

Usage

• Enable toolkit.legacyUserProfileCustomizations.stylesheets in about:config
• Open about:support, click on "Profile Directory → Open Directory" (may also be named "Folder" instead of "Directory").
• Create a new chrome directory and copy userChrome.css to there.

See this post for some more details.

Notes

• Only tested on my Linux system.

• Needs Firefox 91.

• You need to modify the toolbar colour if you use a dark theme.

• If you set browser.compactmode.show to true in about:config you can select "density compact". Dunno how long they will keep this around, but it works for now.

• Set widget.non-native-theme.scrollbar.size if you want a wider scrollbar.

• Set browser.urlbar.maxRichResults if you want more results in the URL bar.

License

Do what thou wilt shall be the whole of the license.