Mozilla is testing a new "Smart Window" in Firefox—a separate, optional window where users can chat with an AI assistant of their choice while browsing. The company is inviting users to join a waitlist to try the feature first.

The window sits alongside Firefox's Classic and Private modes. Users decide when, how, or whether to use AI at all, and can switch the whole thing off if it is not for them. Mozilla's own announcement frames the project as "user-controlled," built so that users are never locked into one ecosystem or forced into an AI experience. The project is still early, and Mozilla says it is building in the open and wants feedback from its first testers.

Mozilla's pitch draws a line with browsers made by AI companies, which Mozilla says force a hard choice: use AI all the time or not at all. Firefox, the argument goes, is the independent option that keeps users in control. The framing arrives in a browser market where Google's Chrome dominates and long-running usage trackers put Firefox's global share in the low single digits. Firefox is also built by the Mozilla Corporation, a subsidiary of the nonprofit Mozilla Foundation—a structure Mozilla has long cited as the basis for its independence.

"In Firefox, you'll never be locked into one ecosystem or have AI forced into your browsing experience. You decide when, how or whether to use it at all," Mozilla says.

The Smart Window extends features Mozilla already ships, including the AI chatbot in the desktop sidebar and Shake to Summarize on iOS.

Browser AI has become a privacy battleground, and the open-source code behind these tools is what allows outside researchers to verify their claims. The stakes are unusually high because a browser sits on nearly everything a user reads, searches, and types, which is why AI features that touch page content draw particular scrutiny. Brave pushed its own LEO assistant, built with Anthropic, as a privacy-first alternative, while other companies are building products that sacrifice privacy for convenience. Perplexity Comet, Microsoft Edge, and Opera Neon are among the biggest AI-centric browsers. OpenAI killed its own Atlas browser to focus on the development of a more generalistic app, and Google tried enhancing its browser with AI by silently downloading a model that runs locally.

Mozilla is also trying to appeal to a broader user base while keeping its privacy-first roots intact: offer the assistant, but make the off-switch the draw. The approach ties back to the Project Nova redesign, which gave Firefox a single control to disable every AI feature at once—a one-click AI kill switch that arrived earlier this year.

Mozilla says AI should be "open, accessible, and driven by choice." The signal to watch from here is how the waitlist testers' feedback shapes the feature, and whether the Smart Window moves from this early experiment into Firefox's standard release builds. For now, the waitlist is open at firefox.com/ai, and the feature stays off unless a user turns it on.