Mozilla has released **Firefox 157**, the first stable version of its web browser to include a major interface redesign called "Project Nova." This update brings rounded corners, a new color scheme, and a more consistent look across both desktop and mobile versions. Changes include redesigned tabs, menus, address bars, and panels, all aimed at creating a "cleaner" appearance and reducing visual clutter. This is the largest visual change in years since the introduction of the Proton interface in 2021. The Nova design is enabled by default and cannot be reverted through standard settings, though users can disable it by adjusting the about:config settings and setting browser.nova.enabled to false. A feature called compact mode has returned, allowing users to reduce the size of tabs and toolbars to make more space for web pages. This mode is now accessible through the "Window Density" section in the appearance settings and activates automatically on smaller screens. It offers four configurations: Standard, Compact, Tactile, and Automatic. Previously, this feature was hidden in advanced settings and had been requested by users for easier access. Firefox 157 also introduces hardware decoding of the AV1 video format during WebRTC calls on compatible devices. This helps reduce heat and battery usage compared to software-based decoding. Previously, such decoding was limited to H.264 on ARM64 devices in Firefox 156. The update also addresses several security vulnerabilities, including 38 critical ones, and removes Amazon from the list of built-in search engines, though users can still add it manually. The redesigned interface features new color themes inspired by Firefox’s branding, with warm glows and deep smoky violets. Icons and menus are now optimized for both light and dark themes, and the New Tab page allows users to customize what appears and pin frequently visited sites. A sidebar, introduced in a previous update, is now enabled by default and includes chatbots, vertical tabs, and shortcuts. Users can disable the sidebar using the sidebar.revamp setting in about:config, though this option will be removed by the end of 2027. Mozilla has also begun integrating AI features, such as the Smart Window with an AI assistant from Mistral AI, which is still in beta. The update includes simplified language in settings menus and a button to disable AI features, though these might not be included in the final version. This release follows Firefox 156, which introduced faster PDF loading and H.264 decoding on ARM64 devices. Firefox 157 is expected to be the first in a series of updates aligned with Mozilla's roadmap, which includes customizable keyboard shortcuts, integrated containers, and further improvements to "Smart Windows."