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

Check your Chrome user data folder. Chances are there’s a 4GB AI model in there, one you never wanted to install. The file is called weights.bin, buried in a folder called OptGuideOnDeviceModel. It’s the weight file for Gemini Nano, Google’s on-device language model.

Delete it and Chrome will download it again.

Privacy researcher Alexander Hanff exposed the behavior while running an automated audit on a new Chrome profile. Using macOS kernel file system logs, he traced Chrome by creating a temporary folder, pulling down model components, and putting the finished file on disk. The whole process took about 15 minutes. No notification. No prompt. The profile had not received any human input at any time.

The same pattern has been confirmed on Windows 11, Apple Silicon Macs and Ubuntu. Users who have been experiencing 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 pasting, page summarization, and AI-assisted tab grouping. In Windows, the file ends up at %LOCALAPPDATA%\Google\Chrome\User Data\OptGuideOnDeviceModel\weights.bin. On Mac and Linux, this is the equivalent Chrome profile folder.

Deleting the folder does not provide lasting relief. Chrome will restore it on the next restart unless you disable the feature: via chrome://flags, the AI ​​switch on the device in Settings > System, or in Windows, a registry edit setting OptimizationGuideModelDownloading to disabled.

Chrome recently added a prominent ‘AI Mode’ pill to the address bar. A reasonable user seeing that button (with a local 4GB model already on their drive) would assume their searches remain on the device. They don’t. AI mode sends every query to Google’s cloud servers. The local Gemini Nano model does not provide any power at all.

You pay the storage and bandwidth costs for a feature that you don’t actually use privately.

Is it legal or ‘legal’?

Hanff claims that Google is violating EU privacy law. His case turns around Article 5(3) of the ePrivacy Directive– the same clause behind cookie consent banners – which requires “prior, voluntarily given, specific, informed and unambiguous consent” before anything is stored on a user’s device. He also cites GDPR articles 5(1) and 25, which relate to transparency and privacy by design.

He also drew a direct line to a case he published two weeks earlier: Anthropic’s Claude Desktop quietly pre-authorized browser automation on approximately three million user machines without explicit permission. It’s the same pattern, he argued, but on a much smaller scale.

However, Google has been sneaking Gemini Nano into Chrome for a while now. People just didn’t notice. “To provide an enhanced browsing experience, Chrome uses on-device AI models to support web and browser features,” Google says in its Support site. “Chrome can download generative AI models on the device in the background so that features that rely on these models remain ready to use on the device. If you delete AI models on the device, only features that rely on them will become unavailable.”

“In February, we started rolling out the ability for users to easily disable and delete the model directly in Chrome settings. Once disabled, the model cannot be downloaded or updated.” the company told Android Authority.

The company noted that the model will be automatically deleted when storage runs low. What Google didn’t discuss is why users weren’t asked first.

Google’s Chrome developer documentation tells third-party developers that it is “best to warn the user of the time required to complete these downloads.” Google didn’t follow its own advice this time.