Mozilla has released Firefox 157 today, September 29, 2026, as part of its bi-weekly release regiment. This stable update introduces what Mozilla describes as the browser’s "biggest visual refresh in years," with the new Nova theme now enabled by default. The Nova theme features rounder, more colorful core UI elements and subtle pastel gradients tinting the window chrome on Windows, macOS, and optionally on Linux. Beyond the aesthetic changes, Firefox 157 also gains WebRTC Hardware AV1 Decode support. This enhancement improves performance for real-time communication protocols that utilize the AV1 video codec.