Mozilla Returns Compact Mode to Firefox as Nova UI Redesign Draws User Backlash

Mozilla is restoring native Compact Mode to Firefox, reviving a density option the company removed in 2017 after users complained that its upcoming Nova UI redesign wastes too much screen space.

The toggle appeared this week in Firefox’s Nightly channel — the browser’s early-access testing build — under Appearance settings in a section labeled Window Density.

Compact Mode Returns to Nightly

Selecting the option immediately tightens the padding around tabs and the Address Bar, pulling interface elements closer together and reclaiming visible screen area for web content.

The setting replicates the behavior of the original compact option Mozilla stripped out in Firefox 89, which launched in 2017 and sparked lasting complaints from productivity-focused users.

By contrast, the Nova UI’s default layout uses pill-shaped tabs and heavily padded borders that push web content further down the Page — A design many longtime users rejected when early previews went public.

Users Built Their Own Fixes First

Impatient users did not wait for an official solution. They circulated custom CSS code — cascading style sheets, the formatting language browsers use to render visual layouts — on the Firefox CSS subreddit to manually strip the rounded styling.

One user, Zonnev, posted a single-line variable to flatten the tab design:

“`css
:root { –chrome-block-radius: 0px !important; }
“`

Another user, Jay33721, published a more comprehensive version that also removes window gaps and strips borders from the main browser container:

“`css
:root {
–chrome-window-gap: 0px !important;
–chrome-block-radius: 0px !important;
–chrome-content-separator-color: transparent !important;
}

.chrome-block {
border: 0px !important;
}

.browserContainer {
border: 0px !important;
}
“`

Applying either fix requires users to enable custom stylesheets through Firefox’s advanced configuration menu, create a chrome folder inside their active browser profile directory, and drop a file named userChrome.css into it.

Broader Pressure on Mozilla

The timing matters. Mozilla faces mounting pressure over Firefox’s user base. A widely circulated report claimed the browser had lost tens of millions of users, though Mozilla disputed the framing of those figures.

Rival browser maker Brave added a similar compact density toggle in a recent Nightly build of its own product, a move aimed at power users who prioritize maximum page visibility.

Mozilla’s 2026 product roadmap also promises native tab groups — a feature that Lets Users organize open tabs into labeled clusters — among several other interface updates.

Firefox Nightly builds update daily and serve as the earliest public testing ground before changes move through the Beta channel and into general release.