Firefox Smart Window beta has arrived in Firefox 153 for MacOS and Windows, offering a free, built-in AI assistant that pulls together chat, tab management, and context-aware browsing without an additional subscription or extension.
A Feature Years in the Making
Mozilla first floated the concept last November under the name ‘AI Window,’ spending several months adjusting functionality before settling on the Smart Window branding, according to Thurrott. The feature is opt-in, and Mozilla added a dedicated AI Controls section in Firefox’s settings where users can disable all AI features entirely, Thurrott reported.
On first launch, Firefox 153 walks users through a brief setup wizard. Rather than presenting raw model names, Smart Window offers three categories: Fast, which runs on Google’s Gemini; Flexible, powered by Alibaba’s Qwen; and Personal, using OpenAI’s gpt-oss-120b. Users can switch between models mid-conversation using a drop-down at the bottom of the chat box.
Mozilla subsequently struck a deal to bring in a fourth option. On 16 September 2026, Mistral AI announced a partnership with Mozilla to add Mistral Small 4 to Smart Window, initially for users in France and North America, with the UK and Germany expected to join later in 2026.
What Firefox Smart Window Beta Offers Day to Day
The chat interface is spare. A ‘+’ icon starts a fresh conversation; a small computer icon to its right toggles the Memories function, which retains details from past sessions so the assistant can maintain context across chats. Memories can be switched off per conversation if privacy is a concern.
Beyond the chat pane, Smart Window layers in context-aware assistance: it reads open tabs and browsing history to generate summaries and answers, integrates with the user’s default search engine for up-to-date results, and handles tab management by grouping or closing tabs by topic. Mozilla partnered with Exa, a web search service built for AI, to power that search layer on the desktop and to drive Quick Answers in Firefox for iPhone and iPad, serving source-backed results without leaving the current page.
Firefox Smart Window beta currently runs on MacOS and Windows. The feature has not yet appeared in Firefox Nightly on Linux, including on Ubuntu and Fedora, though some users have reported seeing it there.
The Rollout Continues Beyond the Beta
Mozilla is pushing Smart Window forward in stages. Firefox 154, released on 18 August 2026, added the ability for Smart Window to suggest groups of related tabs and propose a name for each group, as part of a progressive rollout, according to Releasebot. Firefox 155 then opened Smart Window to all users in the US, Canada, and France, making it the first expansion of the feature beyond North America.
Future updates are also in view. Mozilla’s own Smart Window page states that the browser will gain Chrome-style surfacing of recent browsing journeys and AI-powered autofill for online forms, The Verge reported. Firefox head Ajit Varma told The Verge there is ‘no precise date’ for when Smart Window will exit beta, and noted that users can also select local AI models alongside the listed cloud providers.
The three original cloud models, Google’s Gemini, Alibaba’s Qwen, and OpenAI’s gpt-oss-120b, were in place from the start of the beta before Mistral Small 4 was added via the Mozilla-Mistral partnership, It’s FOSS noted. That expanding roster signals Mozilla intends Smart Window to remain model-agnostic, letting users swap providers as their needs or privacy preferences change.
For users who rely on AI for research but dislike the performance hit of running large local models, Smart Window offers a middle ground: cloud inference when needed, local models as an option, and a privacy-aware design that operates locally where possible. The main gap for power users is the absence of a native Workspaces feature for tab organisation, a capability browsers such as Opera and Vivaldi have offered for some time.
The question is how quickly Mozilla can push Firefox Smart Window out of beta and onto Linux, where a vocal portion of its user base is currently waiting. Varma’s ‘no precise date’ suggests the timeline is tied to stability, not a fixed calendar, meaning the Linux release and the UK and Germany Mistral expansion are the two dates worth watching.