I opened Chrome to check something small and noticed my free space had dipped by several gigabytes overnight. You might shrug and blame temporary files—until you find a 4GB folder called OptGuideOnDeviceModel sitting there without your consent. I walked through the breadcrumbs so you don’t have to.
My Chrome folder suddenly showed a 4GB file — and I didn’t install it
You’re not imagining it: a file named weights.bin has been turning up inside a folder called OptGuideOnDeviceModel on both Windows and macOS machines. Security researcher Alexander Hanff, known online as That Privacy Guy, flagged that Chrome appears to be placing roughly 4GB of AI model data on devices. The model is reported to be Gemini Nano, Google’s lightweight, on-device version of its large language model, used for local features like scam detection and some developer APIs.
This file behaves like a stowaway in your luggage: you didn’t invite it, but it’s there and it can be reinstalled automatically when you restart the browser.
Why is Chrome downloading a 4GB AI model without asking?
Google’s position, shared with outlets such as Gizmodo, is that Gemini Nano runs locally to power security and developer tools without sending your data to the cloud. Their documentation and a Chrome developer API confirm that Chrome can use an on-device model for AI tasks. The company also says the model will uninstall automatically if the device is low on resources and that, as of February, Chrome began rolling out a simple toggle to turn the on-device AI off and remove the model through Settings.
But the rollout hasn’t reached everyone. In practice, the model has been installed on devices that meet minimum hardware requirements without an explicit install prompt or an obvious opt-out — and if you manually delete the files, Chrome has been observed re-downloading them quietly on restart.
I found conversations about the same folder across Reddit and support forums
Across Reddit threads, Superuser posts, and Chromium discussion groups, users have been asking what the OptGuideOnDeviceModel folder is and how to remove it. That independent chatter lines up with Hanff’s report and with Chrome’s own docs and policies that note software updates may be applied automatically when Google changes features.
That consensus makes the surprise feel less like a mystery and more like an intentional behavior buried under default settings and terse legal text.
Can I delete Gemini Nano from Chrome?
Yes, but with caveats. First, check whether the model is present by typing chrome://on-device-internals into the omnibar; it will show the model and its disk footprint. If your Chrome has received Google’s toggle, go to Settings → System and flip Turn On-device AI on or off. That will stop further downloads and remove the model.
If you don’t have the toggle yet, Hanff and community members suggest a few workarounds: disable AI-related chrome://flags entries to prevent automatic re-downloads, or set the weights.bin file to read-only. Some people manually delete the folder, but expect odd browser behavior and the loss of any Chrome AI features. Deleting the model can break those features and, in some reports, make Chrome act a bit funky.
I asked what Google publicly says — and their terms quietly cover it
Google’s quoted response notes Gemini Nano has been available in Chrome since 2024 and is meant to run locally for privacy-sensitive tasks like scam detection. Their public terms say Google sometimes adds or removes features and that software tied to services may update automatically on your device.
That wording reads like a legal umbrella under which the downloads happen, but it’s not the same as a clear, upfront permission prompt. It’s as if a silent architect were rewriting part of your house while you’re at work.
Practical steps I recommend you try right now
Check chrome://on-device-internals. If you see the model and want it gone, first look for the Settings toggle. If the toggle isn’t available, you can:
- Disable AI-related flags at chrome://flags to reduce the chance of re-downloads.
- Make weights.bin read-only so Chrome cannot overwrite it.
- Be prepared for some AI features to stop working and for possible odd behavior after removal.
Hanff has independently demonstrated the install and re-download behavior on both Windows and macOS, and the issue has been discussed by communities on Reddit and Superuser as well as in Chromium group threads.
How this matters for privacy, performance, and trust
Seeing multi-gigabyte AI data land on your drive without an explicit prompt raises three questions: who decides what runs on your device, how much disk and memory you should expect to sacrifice, and whether local models truly keep data out of the cloud. Google insists the model is local to protect privacy and that it won’t download if storage is low, but the lack of upfront consent sows distrust.
For security-minded users, the trade-offs are clear: local AI can reduce cloud exposure, but silent installs erode control. For corporate IT teams, a 4GB footprint per browser install can become a logistic problem when scaled across devices.
If you found an unexpected 4GB blob on your machine, will you accept Google’s quiet housekeeping or reclaim control from your browser?