Firefox 157: Nova's New Look, Compact Mode's Return and Open Accessibility Gaps

Firefox 157 has rolled Mozilla's biggest redesign since Proton to everyone: new colours, softer tabs, a reworked sidebar and the official return of Compact Mode, worth about ten extra pixels of web content. In an interview Mozilla acknowledges remaining problems with keyboard focus, screen reader announcements and contrast, and names the end of 2027 as the deadline for the fallback to the old sidebar.

Key Takeaways

Firefox 157 has rolled Mozilla's biggest redesign since Proton to everyone: new colours, softer tabs, a reworked sidebar and the official return of Compact Mode, worth about ten extra pixels of web content.
In an interview Mozilla acknowledges remaining problems with keyboard focus, screen reader announcements and contrast, and names the end of 2027 as the deadline for the fallback to the old sidebar.

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For five years the Proton design defined Firefox's face. With Firefox 157, rolled out to everyone on September 29, Mozilla has given the browser new colours, softer tab shapes and a reworked sidebar — and brought back the Compact Mode that many users had been forcing on through about:config since the last redesign. In an interview, the Mozilla team explained which criticism from the testing phase actually changed something and which did not.

Compact Mode is officially back. An earlier draft of the redesign placed a margin at the outer window edge; community feedback showed it made clicking at the window border harder, so it was removed. The new tab shapes and gradients, by contrast, came under fire on Reddit, but tests with a broader group of people produced a different picture, and Mozilla kept them. For small screens or two windows side by side, Mozilla argues, 'even a few pixels count'.

The gain is modest and concrete: roughly ten more pixels of space for web content, depending on whether horizontal or vertical tabs are used. Mozilla reduced the spacing between elements but kept the controls themselves almost as large as in the standard view. Window density is set under Settings > Appearance > Window density; with 'Automatic' selected, Firefox switches to Compact Mode when the tab bar takes more than 5% of the window height, or the collapsed sidebar more than 5% of the width — a proportional rule that adapts to themes, fonts, operating systems and display scaling.

The new sidebar is technically coupled to vertical tabs. Restoring the old sidebar also removes vertical tabs, which were never compatible with the older version. The fallback option is to remain until the end of 2027; whether it survives longer depends, Mozilla says, on usage and the maintenance effort of the old code. Once the fallback and its underlying code are removed, switching back will no longer be possible.

Accessibility is a work in progress. Mozilla tested keyboard operation including focus in the sidebar, panels and tab list, screen readers such as NVDA on Windows and readers on Linux, Windows high-contrast mode, and layout at high scaling. Most problems were fixed, but issues remain with keyboard focus and navigation in some panels, labels and announcements for screen readers, the contrast of some controls, and tab visibility at very high display scaling. These are tracked in Bugzilla.

Mozilla says it will judge the redesign's success a year from now by whether people keep choosing Firefox as their everyday browser. The company's own walkthrough of the changes is on Mozilla Connect, and a week after the big update Firefox 157.0.1 arrived with fixes for Windows backup setup, macOS downloads and a moderate security flaw.