Mozilla began rolling Firefox 157 out to the Release channel on 29 September. It is the first stable build to carry the interface redesign its developers worked on as Project Nova, and the first that can decode AV1 video inside WebRTC calls in hardware on machines whose graphics hardware supports it.
The release date needs one qualification. Phoronix reported the binaries as available on 28 September, and BetaNews and Linuxiac both date the release to 28 September. Mozilla’s own notes say version 157.0 was first offered to Release channel users on 29 September. The likeliest reading is that the builds reached Mozilla’s file servers on the 28th and the staged rollout to existing installations began the next day; Mozilla’s release notes are the authority for the rollout date.
Firefox 157 rebuilds the browser chrome on a revised design system: updated toolbars, sidebar and menus, more consistent rounded corners, icons refreshed for both light and dark themes, and rebalanced spacing, which Linuxiac and BetaNews describe as the browser’s biggest visual overhaul in years. The name Nova comes from the coverage rather than from Mozilla’s release notes; BetaNews reports the Firefox UX team saying Nova refers to the design update and is not a separate product. The release also ships built-in themes with light and dark variants, and brings back compact mode, which reduces toolbar and tab spacing. BetaNews reports that the code behind it never actually left Firefox, it simply stopped being offered in the interface years ago.
The AV1 change is the one with a hardware dependency. AV1 video in WebRTC calls was previously always decoded in software, which put the work on the processor regardless of the graphics hardware installed; on supported devices Firefox 157 can hand it to the GPU instead, with no setting to enable. Phoronix and BetaNews both report the change, and none of the sources list which devices qualify, so whether a given machine benefits depends on its own hardware.
Amazon is no longer among Firefox’s built-in search engines, although it can still be added manually as a custom search engine. Phoronix, BetaNews and Linuxiac all report the removal; Mozilla’s release notes do not mention it. Those notes do list an expansion of localized address-bar suggestions through Firefox Suggest to a further set of European countries, including Austria, Belgium, the Czech Republic, Denmark, Finland, Hungary, Ireland, Luxembourg, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden and Switzerland.
Several long-standing bugs are fixed. On Windows, HDR video in some 8-bit formats no longer plays back looking dull and grey, and the taskbar no longer stays visible over fullscreen video. Audio and video synchronization no longer drifts when playback speed is changed repeatedly, such as while watching YouTube. Selecting an address-bar suggestion while a page is still loading now opens the suggestion instead of searching for the typed text.
Two security and interaction changes are worth noting. Firefox now displays a warning in the site information panel, and in Settings, when it has been configured to record its own encryption keys, a setup that could let other software on the same computer read encrypted web traffic; Mozilla’s release notes describe the warning. And pressing Tab in the address bar now moves focus straight to the text field rather than stopping on the search engine button, which remains reachable with Shift+Tab.
One item is unresolved. Mozilla’s beta release notes for Firefox 157 listed plainer-language settings menus and a toggle to disable AI features entirely. Mozilla’s summary of the stable release mentions neither, so whether either shipped is unclear.
Mozilla’s servers publish the 157 binaries, and existing installations update automatically over the coming days. Most Linux users will receive the release through their distribution’s package repositories rather than from Mozilla directly.