Firefox 157 Brings Back Compact Mode as Part of Mozilla's Nova Redesign

Firefox 157 lands as part of Mozilla's ongoing Nova redesign, and the headline change for anyone who has missed an older, denser Firefox is the return of compact mode, an interface density option that shrinks the toolbar and tab strip back down after several releases without it.

On the developer side, 157 adds support for the at-rule() function inside @supports, letting a stylesheet test whether a browser understands a given at-rule before relying on it, and a new chain value for the overscroll-behavior property, giving finer control over whether scroll momentum passes from a nested element out to the page behind it. Neither is a flashy addition, but both close small, genuinely annoying gaps that CSS authors have worked around with JavaScript for years.

The release also improves audio and video sync when a user changes playback rate on an HTML media element, and handles HDR video encoded in 8 bit colour formats more correctly, both the kind of fix that matters enormously to the person hitting the bug and invisibly to everyone else.

What is worth watching is less any single feature than the cadence. Mozilla moved Firefox from a four week release cycle to two weeks this September, following Chrome down the same path a few weeks earlier. Faster releases mean smaller, lower risk changes ship more often, which is generally good for stability, but it also means the gap between a feature shipping in a release note and actually reaching most users compresses fast enough that browser support tables need checking more often than habit currently allows.

Compact mode returning is a small win on its own, but it is also a sign Mozilla is willing to walk back a Nova decision that a vocal chunk of its user base clearly did not want, which says something reasonable about how the redesign is being run.