Chrome Is Quietly Installing a 4GB AI Model on Your Computer—And Putting It Back If You Delete It

In brief

• Chrome silently downloads a ~4GB Gemini Nano file called weights.bin to eligible devices with no opt-in prompt, and automatically re-downloads it if deleted.
• Chrome's "AI Mode" button in the address bar routes queries to Google's cloud servers—the local 4GB model doesn't power it.
• Privacy researcher Alexander Hanff argues the behavior violates the EU ePrivacy Directive.

Check your Chrome user data folder. There's a decent chance a 4GB AI model is sitting there—one you never agreed to install. The file is called weights.bin, buried in a folder named OptGuideOnDeviceModel. It's the weight file for Gemini Nano, Google's on-device language model.

Delete it and Chrome downloads it again.

Privacy researcher Alexander Hanff uncovered the behavior while running an automated audit on a fresh Chrome profile. Using macOS kernel filesystem logs, he traced Chrome creating a temp directory, pulling down model components, and placing the finished file on disk. The whole process took roughly 15 minutes. No notification. No prompt. The profile had received zero human input at any point.

The same pattern has been confirmed on Windows 11, Apple Silicon Macs, and Ubuntu. Users who've been finding unexplained storage spikes for over a year now have a name for the culprit.

What it actually does

Gemini Nano powers Chrome's on-device AI features: Things like "Help me write an email," scam detection, smart paste, page summarization, and AI-assisted tab grouping. On Windows, the file lands at %LOCALAPPDATA%\Google\Chrome\User Data\OptGuideOnDeviceModel\weights.bin. On Mac and Linux, it's the equivalent Chrome profile directory.

Deleting the folder provides no permanent relief. Chrome restores it on the next restart unless you disable the feature—via chrome://flags, the On-device AI toggle in Settings > System, or on Windows, a registry edit setting OptimizationGuideModelDownloading to disabled.

Chrome recently added a prominent "AI Mode" pill in the address bar. A reasonable user seeing that button—with a 4GB local model already on their disk—would assume their queries stay on-device. They don't. AI Mode routes every query to Google's cloud servers. The local Gemini Nano model doesn't power it at all.

You're paying the storage and bandwidth cost for a feature you're not actually using privately.

Is it legal or “legal”?

Hanff argues Google is violating EU privacy law. His case centers on Article 5(3) of the ePrivacy Directive—the same clause behind cookie consent banners—which requires "prior, freely-given, specific, informed, and unambiguous consent" before storing anything on a user's device. He also cites GDPR Articles 5(1) and 25, covering transparency and privacy by design.