Multiple Rows of Tabs in Firefox 89 (Proton)

One of my essential tools is having multiple rows of tabs in Firefox. Yes, I’ll admit it– I often open many, many tabs at once while doing research. And even when I’m not doing research. Multi-row tabs should come built in and accessible with a config setting, but it doesn’t. Over the years I had been using snippets of custom CSS I downloaded from random places on the Internet to do it. But the recent Firefox update (89) introduced a new user interface style called Proton that’s on by default. It broke my multi-row tabs…

So how do I get it back?!?

It took some research, but I found a good way to do it. With this change, I love the new Proton UI. And I have multi-row tabs back. Clone or download this git repository:

The Proton configuration is in this file: multiple_tab_lines.css – install that as the userChrome.css file or add the contents to a userChrome.css file. Here’s the directions in the file:

1. Open profile folder: address bar > about:support > Profile Folder > Open Folder
Create “chrome” (sub)folder.
Save this file as ‘userChrome.css’ inside “chrome” folder or add code to an existing userChrome.css file.

2. Open config area: address bar > about:config > modify/add the following values/settings:

toolkit.legacyUserProfileCustomizations.stylesheets > true || enables custom style sheets > true || shows ‘Compact mode’ in customizing mode
browser.uidensity > 1 || enables compact mode
browser.proton.enabled > true || enables proton mode
browser.proton.contextmenus.enabled || enables proton context menus
browser.proton.doorhangers.enabled > true
browser.proton.modals.enabled > true
browser.proton.places-tooltip.enabled > true

3. Restart browser

It’s magic – the new multi-row tabs look like they were built in. Thank you aris-t2!

If you want this feature to be built in to Firefox, you can comment on this Firefox Bugzilla bug and say so.