Since Firefox 69, you have to enable toolkit.legacyUserProfileCustomizations.stylesheets in about:config for userChrome and userContent to be loaded at all as per bug #1541233.
If you only want multirow or any other function that isn't related to the theme (like tabs below, or focus tab on hover), you can use the installers inside the releases section.
For anyone looking for the old code like the dark theme or the attempt of a mod loader, you can find it in the backup/2025-09-12 branch.
Files updated:
- Multirow*uc.js: Fixed some issues while moving tab groups.
Files updated:
- Removed the full dark theme, since it has been broken for a while.
- Removed the custom mod loader, since it was too ambitious and required a major rewrite.
- Left all the old code at backup/2025-09-12 branch
You can find some of the basic settings that can be simulated through about:config, some userscripts, and some addons here.
You can enable multirow tabs as well as other functions using the installer in the releases section, or following the methods explained inside Multirow and other functions folder.
If you are using Linux or Mac, or want to add some more functionability (like deleting some useless context menu commands), you will have to use the methods described inside one of the 3 main folders of this repository:
- CSS tweaks: Enables removal of context menu items, multirow bookmarks, changing tab bar position (so that it could be under the bookmarks bar for example).
- Multirow and other functions: You can find the JS files that add extra functionability to Firefox that couldn't be done with CSS alone.
You can find an all-around sites stylesheet that will paint every site you visit dark here. You need Stylus addon to use it.
While it's not perfect (meaning that you should still use per-site styles for the sites you visit often), it can help to darken most sites when browsing around general sites that you don't visit often, and thus don't want/can't find a specific userstyle for them.
You can find the frequently asked questions in here.
The original code for the multirow tabs (the CSS part) was written by Andreicristianpetcu, and you can find it here, or for just the code, here. The fix of multi-row tabs draggability was made by TroudhuK, and you can find the original one here.
The original code for the multirow bookmarks toolbar belongs to the original creator mentioned in this reddit thread, whose code was fixed by jscher2000 to use in our current firefox version.
The fix to be able to theme unread tabs again after FF61 (see bug #1453957 on bugzilla) as mentioned in this reddit thread, was made by moko1960 to use in Firefox 61+.
A fix for multiple tab reordering and another fix for the new tab button to not start a row on its own without a tab on multirow was made by Merci-chao.
The code to be able to edit anonymous content (in our case the scrollbars and tooltips) was created thanks to the efforts of Zeniko, Nichu, and Sporif in the old versions, and Xiaoxiaoflood for the current one.
Special thanks to Messna for noting the class turning into an ID on FF58, and Snwflake for fixing Firefox root folder location on MacOS.
Also thanks to 532910, BelladonnavGF, DallasBelt, Demir-delic, Gitut2007, Hakerdefo, Pauby, Tkhquang and YiannisNi for noting some issues with the theme, and the requests for new features that extended this project.