Restore Square Tab Corners in Firefox

Firefox's Nova refresh rounded off the tab strip, and plenty of longtime users want the older rectangular look back on their computer.

One preference in about:config handles it: set browser.nova.enabled to false and the tabs square off immediately. No reinstall, no lost bookmarks.

In this guide, I have covered:

Why your Firefox tabs suddenly look rounder

You updated Firefox, opened it, and the tabs came back with soft curved corners instead of the sharp ones you’re used to. That’s Nova, the interface refresh that ships rounded tab corners, a softer title bar, and a tighter tab strip as the default in recent Firefox releases.

Nothing is broken, and your profile hasn’t changed. One about:config preference controls the new look, so you can turn it off without uninstalling Firefox or losing a single bookmark. Flip it and the tabs go back to the rectangular shape from the older Proton UI.

Disable the Nova tab design in about:config

You don’t need an add-on or a custom stylesheet for this. The rectangular tabs are still in current builds, just hidden behind one preference you can flip yourself.

1. Open a new tab, type about:config in the address bar, and press Enter.
2. Click Accept the Risk and Continue on the warning page.
3. Type nova in the search box at the top and press Enter to filter the list.
4. Find the row labeled browser.nova.enabled. The value column should read true.
5. Click the toggle button at the far right of that row, or double-click the row, to switch the value to false.
6. Switch back to the main browser window and check the tab strip. The tabs should already look rectangular, no restart needed.

With the preference set to false, Firefox falls back to the pre-Nova layout for the tab strip and the other surfaces Nova restyles.

The browser.nova.enabled preference is scheduled for removal in Firefox 161, expected late November 2026. Until then, it works on the current stable build and the next two releases. After Firefox 161, the built-in way to disable Nova is gone, and Mozilla is expected to keep Nova as the default look.

Confirm the change worked

Open a few new tabs so the strip fills out, then look at the corners. You’ll know it worked when the edges are squared off again instead of curving into the Nova shape.

For a second check, go back to about:config, search browser.nova.enabled, and confirm the value column reads false. The title bar is another tell: the Nova gradient disappears once the flag is off.

What to do if the change doesn’t stick

You flipped the toggle and the tabs still look rounded. Work through these checks in order. One of them usually explains it.

• Make sure you toggled browser.nova.enabled and not a similar name. Other prefs on the same page, such as browser.newtabpage.activity-stream.nova.enabled and pdfjs.enableNova, don’t control tab shape.
• Restart Firefox. Most people see the change live, but some report it only applies on the next launch.
• Check your Firefox version. The toggle exists in the current stable build and the next two releases. On an older build, update first.
• Disable any theme that might be redrawing tabs. Compact and dark themes can restyle the tab shape and mask the toggle.
• Try a fresh Firefox profile to rule out a leftover userChrome override from an earlier tweak.

If none of that helps, refresh Firefox from the troubleshooting page to reset preferences and disable extensions. Bookmarks, history, and saved logins are kept. The steps in our guide to resetting Firefox settings cover the whole process.

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