Firefox Project Nova: From Design Preview to Firefox 157
Mozilla's Project Nova design refresh began rolling out with Firefox 157 on September 29. Read what changed and where to review AI memory settings.
TL;DR
- —Project Nova was the internal name for Firefox’s design and design-system refresh, announced in May 2026.
- —Mozilla says the new design began rolling out with Firefox 157 on September 29.
- —The release includes Compact Mode and customization changes. Review AI and privacy settings separately.
Updated October 3, 2026: The announced design is now rolling out. This update replaces the earlier future-tense release description and removes unsupported assurances about extension compatibility. Mozilla introduced Project Nova in May as work on Firefox's interface and design system. The original announcement describes changes to colors, spacing, icons, and access to privacy controls. It does not announce a replacement browser engine. On September 29, Mozilla said the design began rolling out with Firefox 157. The release brings back Compact Mode, changes theme selection, and adds a dedicated space for New Tab shortcuts. Check the installed version and available controls on your device rather than assuming every rollout has reached every user. A design change is not evidence that an extension will work, that a setting is private by default, or that an AI feature processes everything locally. Our Firefox 157 settings report explains the distinction between memory storage, server processing, and deletion in Smart Window.