Google Chrome has apparently been silently downloading a 4GB AI model onto your device without asking. Easy to delete, right? Sure, but Chrome will redownload it.
This whole thing was uncovered by privacy researcher Alexander Hanff, who first reported that Chrome has been quietly writing a file called weights.bin to disk. The file is roughly 4GB and lives in a folder called “OptGuideOnDeviceModel” inside your Chrome directory. What is it? It’s the on-device weights for Gemini Nano, Google’s lightweight AI model.
On Windows 11, you’ll find it at %LOCALAPPDATA%GoogleChromeUser DataOptGuideOnDeviceModel. It’s also been confirmed on Apple Silicon Macs and Ubuntu machines. And here’s the kicker: there’s no indication that this is being downloaded. It’s just being downloaded in the background. The download triggers when Chrome’s AI features are active, which they are by default in recent Chrome versions.
The bigger problem isn’t the storage
Sure, 4GB can be a significant amount of storage, especially if you’re on a 256GB MacBook or a metered data plan where 4GB might literally be your entire monthly allowance. But the more frustrating part is the misdirection. Chrome 147 displays a prominent “AI Mode” pill in the address bar, which a reasonable person would assume is powered by that local Gemini Nano model sitting on their disk. It’s not. AI Mode routes every query to Google’s servers anyway. The on-device model is actually used for buried features like “Help me write,” which most people will never use.
So you’re paying the storage and bandwidth costs for a local AI model, while the headline AI feature you actually use goes through Google servers anyway. Hanff has also formally accused Google of violating EU privacy regulations, since the ePrivacy Directive requires explicit consent before storing data on a user’s device.
If you want to stop it, head to chrome://flags, search for “optimization guide on device,” and set it to disabled. On Windows, you can also tweak the registry to permanently block it. Otherwise, uninstalling Chrome is the only foolproof option.
This is the kind of Gemini overreach that will keep happening unless Google actually starts asking first.
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