Chrome quietly installs a 4GB AI model on your computer, bringing it back if you delete it

Check your Chrome user data folder. There’s a good chance there’s a 4GB AI model out there, one you never agreed to install. The file is called weights.bin, and it’s buried in a folder named OptGuideOnDeviceModel. It’s the weight file of the Gemini Nano, Google’s on-device language model.

Delete it and Chrome will download it again.

Privacy researcher Alexander Hanff open Behavior while performing an automatic audit on a new Chrome view. Using macOS kernel file system logs, he traced Chrome to create a temporary directory, pulled out the model components, and placed the final file on disk. The whole process took about 15 minutes. No notice. There is no prompt. The profile did not receive any human input at any time.

The same pattern has been confirmed on Windows 11, Apple Silicon Macs, and Ubuntu. Users who found an unexplained spike in storage space for over a year now have the name of the culprit.

What it actually does

The 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 is located at %LOCALAPPDATA%\Google\Chrome\User Data\OptGuideOnDeviceModel\weights.bin. On Mac and Linux, this directory is the equivalent of a Chrome profile.

Deleting the folder does not provide any permanent relief. Chrome restores it on the next reboot unless you disable the feature — via chrome://flags, toggling AI on the device in Settings > System, or on Windows, the OptimizationGuideModelDownloading registry editing setting is disabled.

Chrome recently added a prominent “AI Mode” tweak to the address bar. A sensible user who sees this button – with a local 4GB model already on their disk – will assume that their queries remain on the device. They don’t. AI mode routes every query to Google’s cloud servers. My local Gemini Nano model doesn’t turn it on at all.

You’re paying the cost of storage and bandwidth for a feature that you don’t actually particularly use.

Is it legal or “legal”?

Hanf argues that Google is violating EU privacy law. His case revolves around 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 anything is stored on a user’s device. It also cites Articles 5(1) and 25 of the GDPR, which cover transparency and privacy by design.

He also drew a direct line to a case he posted two weeks ago: Anthropic’s Claude Desktop silently automated the browser across nearly three million user devices without explicit consent. It’s the same pattern, but on a much smaller scale, he said.

However, Google has been sneaking Gemini Nano into Chrome for a while now. People didn’t notice it. “To provide an improved browser experience, Chrome uses on-device AI models to help power web and browser features,” Google says in its report. Support site. “Chrome may download generative AI models to the device in the background, so features that depend on those on-device models remain ready for use. If you delete on-device AI models, only features that depend on them will be available.”

“In February, we started rolling out the ability to easily turn off and remove the form in Chrome settings. Once disabled, the form will no longer be downloaded or updated.” Company He said Robot body.

The company notes that the model is automatically deleted if storage capacity gets low. What Google doesn’t address is why users don’t ask first.

Google own Chrome developer documentation It tells third-party developers that “it is best practice to alert the user of the time required to perform these downloads.” Google did not follow its own advice this time.