Firefox 157 he made his official debut carrying with him Novathe interface redesign announced by Mozilla in May and then refined for months in the Nightly channel. The change is visible at a glance: tabs, address bars, search boxes and sidebars sport rounder corners and an overall softened design. The goal is to make navigation faster to use and more customizable – how much it succeeds in practice, daily experience will tell.
Among the most concrete news is the return of Compact modewhich reduces the spacing between interface elements to gain vertical space on the screen. Designed for smaller displays or with reduced resolutions, it is activated from the Appearance section of the Settings. It had disappeared some time ago and its absence had generated widespread complaints: its reintroduction is one of the most appreciated points of this update.
Under the hood: AV1 hardware, HDR and vertical sidebar
On the technical front, Firefox 157 adds the AV1 hardware decoding for WebRTC streamsthe protocol used for browser video calls. Where the hardware supports it, this lightens the load on the CPU compared to previous software decoding, with real efficiency benefits during long calls. The update also brings fixes to the HDR rendering issues on Windowsimproves audio/video synchronization during playback speed changes, and fixes the bug where the Windows taskbar persisted over full-screen videos.
Nova then introduces new built-in light and dark themes and optimizes the handling of vertical tabs in the sidebar – a feature that Mozilla is clearly pushing as an alternative to the horizontal tab bar. Amazon, meanwhile, disappears from the list of default search enginesalthough it can still be added manually by users.
Those who don’t like the new look have a way out: the Nova interface can be disabled typing about:config and bringing on false the parameter browser.nova.enabled. A safety valve that Mozilla has left open, at least for now. On the AI front, last week Mozilla announced the integration of Mistral’s Small 4 model for the Smart Window function, which analyzes the content of open tabs to help the user organize the browsing session – currently only available outside Italy.
