Make Firefox’s Tabs Smaller

Or, getting my hands on every pixel possible

Quick Steps

1. In Firefox’s address bar, type about:config and press enter.
2. Note the warning, and “Continue” if you are comfortable
3. In the search bar, search for uidensity
4. Change the 0 value of browser.uidensity to 1
5. The effect is immediate

After Firefox 89’s interface update in 2021 there was a not-so-subtle change made to the way tabs were displayed. They floated now! A neutral change, in my opinion, but something else happened, too. They grew, and were now taking up additional space! How much? I’m not quite sure, but they’re definitely bigger by a few pixels.

This didn’t bother me enough to go searching for a fix immediately. No, this was a “I’m bored, I wonder if there’s a fix for this” type situation.

So there I was, poking around in about:config scrolling through options, changing things, reverting them, and then I came across another that looked intriguing. browser.uidensity . It sounded like what I wanted!

browser.uidensity is set to 0 by default, but if you double click it or press the Pencil/Edit button on the left and change the 0 value to 1. The change takes immediate effect! That’s it!

Enjoy your additional 13 pixels!

And of course, if you wish to revert the change, run through the process again and press the Reset button next to the Edit button, or simply change the 1 back to a 0.

You can also revert in the GUI. Changing the default value of uidensity enables an option in the “Customize Toolbar…” page. Selecting “Normal” here will get you back to defaults.