Mozilla Released Firefox 157 With Nova Theme

The update improves HDR video support and hardware decoding for WebRTC calls in the browser.

Updated on Sept. 28, 2026 in Artificial Intelligence

Bold flat-color editorial illustration in navy, cream, and orange, depicting a geometric prism and cube representing software performance optimization. — Mozilla has released Firefox 157, introducing the new Nova interface theme and improving hardware AV1 video decoding for WebRTC communication. AI Illustration. Upload story photo >

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Do you prefer frequent design updates to your primary web browser?

Mozilla has released Firefox 157, a version that introduces the new Nova interface theme and expands display configuration options. This release also marks the removal of Amazon as a built-in search engine.

Why it matters

The release shifts the browser's display and performance capabilities, particularly for media-heavy workflows. The update reflects a strategic change in search partnerships and interface design for the Firefox ecosystem.

Firefox 157 introduces hardware AV1 decoding for WebRTC video calls and expands HDR video support to include 8-bit color formats. Additionally, the browser now includes native support for detecting browser compatibility with specific CSS at-rules.

The players

Mozilla

A non-profit organization focused on maintaining the Firefox web browser and open-source internet standards.

The details

The Nova theme introduces customizable display modes, including Compact, Standard, and Touch interfaces. The update also modifies the behavior of the Vertical Tabs sidebar, ensuring it functions correctly during full-screen usage. Hardware AV1 decoding—a royalty-free video coding format designed for efficient transmission—is implemented to reduce CPU overhead during WebRTC video communication.

July 2026: Nova design previewed in Firefox Nightly.
September 28, 2026: Mozilla published final Firefox 157 builds.
September 29, 2026: Official Firefox 157 release unveiling.

The Tech Race

The addition of hardware AV1 decoding aligns Firefox with the broader industry transition toward this high-efficiency codec. This implementation optimizes browser performance for real-time communication against competing browser engines adopting similar hardware acceleration standards.

Users can access the update immediately by downloading browser binaries or source tarballs from the Mozilla server. The transition to the Nova theme and new tab sidebar behavior will require users to adjust their interface preferences upon installation.

The takeaway

Firefox 157 prioritizes media performance and visual customization over legacy search partnerships. Users should monitor future patch notes for stability updates related to the new Nova theme and tab interface.