Mozilla released Firefox 157 to the Release channel on 29 September, and calls the update its biggest visual refresh in years. Toolbars, the sidebar, menus and individual features all get the treatment, built on an updated design system.
Two changes will be immediately visible. First, new built-in themes in light and dark versions, letting users re-skin the browser in one click. Second, a new compact mode that reduces toolbar and tab spacing to leave more room for web content - aimed at smaller screens and split-screen layouts.
There is real engineering underneath as well. WebRTC video calls can now use hardware AV1 decoding on devices that support it, instead of always decoding AV1 in software. Firefox also now shows a warning - in the site information panel behind the shield icon and in Settings - when it has been configured to record its own encryption keys, something that could let other software on the machine read encrypted web traffic.
Address-bar suggestions expand too: Firefox Suggest now appears in 16 additional European countries, including Austria, Belgium, Czechia, Denmark, Finland, Hungary, Ireland, Luxembourg, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden and Switzerland. Amazon is no longer a built-in search engine, though it can still be added manually.
The sidebar comes with a decision attached. The updated sidebar is now enabled for everyone and the "Show sidebar" option has been removed from Settings. Anyone who preferred the previous version can still restore it in `about:config` by setting `sidebar.revamp` to `false` - which also turns off vertical tabs. Mozilla says the preference will remain available until the end of 2027.
Smaller changes round out the release: pressing Tab now moves focus straight to the text field of the address and search bars rather than stopping on the search-engine button first, and page dialogs such as `alert()`, `confirm()` and `prompt()`, along with colour and date pickers and form autocomplete menus, now follow the page's light or dark colour scheme. Fixes include videos from phones and tablets appearing sideways or upside down in WebRTC calls, HDR videos encoded in 8-bit formats looking dull on Windows, and the Vertical Tabs sidebar failing to reappear at the screen edge in full-screen mode. Twenty-one of the contributors credited in this release were brand-new volunteers.
