Firefox 155 Launches With AI Smart Window and Faster Page Loads

Mozilla released Firefox 155 on September 1, 2026, marking the first update under a new, accelerated two-week release cycle. The update introduces significant performance enhancements, expands its AI-powered Smart Window feature to more users, and addresses several long-standing bugs, particularly for Linux users.

The most prominent user-facing feature is the broader rollout of Smart Window, an optional AI browsing mode. The feature is now available to users in the United States, Canada, and France. Smart Window provides an AI assistant that can access open tabs and browsing history with explicit user permission, offering personalized conversation starters to resume previous topics and faster responses with cited sources from Exa web search. It also includes an Organize Tabs function that suggests smarter groupings for related tabs. Mozilla positions Smart Window as one of several window types, alongside private and classic browsing, rather than a default experience.

Under the hood, Firefox 155 delivers major networking upgrades aimed at faster page loads. The implementation of Happy Eyeballs v3 allows the browser to race multiple connection methods simultaneously, testing...