Firefox 157

Firefox 157 (released September 29, 2026) delivers the biggest visual refresh in years, modernizing toolbars, sidebar, menus and feature surfaces using an updated design system. It adds new one‑click built-in light and dark themes and a compact mode to reduce toolbar and tab spacing for smaller screens and split‑screen use. WebRTC video can now use hardware AV1 decoding where supported, and Firefox will warn in the site information panel and Settings if it has been configured to record encryption keys (which could let other local software read encrypted web traffic). Firefox Suggest address‑bar suggestions are expanded to several European countries (Austria, Belgium, Czech Republic, Denmark, Finland, Hungary, Ireland, Luxembourg, Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland) and are controllable in settings. Firefox no longer supports Windows 8.1 and macOS 10.14 and earlier; those users are directed to ESR builds.

This release fixes multiple WebRTC orientation issues, an address‑bar selection bug during page load, HDR playback issues on Windows for some 8‑bit videos, audio/video sync when repeatedly changing playback speed, vertical‑tabs and full‑screen taskbar glitches, plus various security fixes. Tab now focuses directly into the address/search text field; Amazon is removed as a built‑in search engine; the updated sidebar is enabled by default and the legacy sidebar can be restored via sidebar.revamp=false in about:config until end of 2027 (this also disables vertical tabs). Web dialogs and pickers now follow page light/dark schemes. Developer additions include at-rule() support in @supports and the chain value for CSS overscroll‑behavior. The release notes also point to enterprise policy details and acknowledge 21 first‑time community contributors.