https://www.tomshardware.fr/vous-avez-perdu-4-go-sans-savoir-pourquoi-chrome-en-est-surement-responsable/
Have you lost 4GB without knowing why? Chrome is probably the culprit
The browser automatically installs files related to Gemini Nano without user consent, and even if users delete them, they are downloaded again.
In recent months, some Google Chrome users have noticed a decrease in disk storage space for no apparent reason or unusual activity on their storage devices. The culprit is believed to be a folder named “OptGuideOnDeviceModel”, located within the Chrome directory and containing approximately 4GB of files related to Gemini Nano, a language model developed by Google.
These files are downloaded by Chrome without the user's knowledge and no separate consent is required. On Windows 11, the folder is located at the following path:
%LOCALAPPDATA%\Google\Chrome\User Data\OptGuideOnDeviceModel
This phenomenon has also been observed on macOS devices with Apple silicon chips and in Ubuntu environments.
Continuously repeating downloads
Even if you manually delete this folder, the problem is not fundamentally solved. Chrome automatically downloads it again. The only way to completely remove it is to delete the browser itself.
However, there is a setting that can disable this behavior. Enter "chrome://flags" in the address bar and search for the "Enables optimization guide on device on Android" entry. Change the menu item to "Disabled". This page also allows you to check whether your device is subject to this feature.
User reports for a year
According to Alexander Hanff, an IT professional and lawyer who analyzed file system logs on macOS to verify this behavior, users have been reporting these automatic downloads for about a year. This coincides with the introduction of several AI features in Chrome last fall, including writing assistance, automatic summarization, and AI-powered search functionality.
Interestingly, the most prominent AI feature in Chrome, the address bar and Google Search integrated AI mode, does not use these local files and operates from Google servers. In reality, the 4GB of data being downloaded is only used for writing assistance and some hidden AI features.
Potentially significant impact, difficult to measure
Given that Chrome is a browser used by billions worldwide, the number of affected devices and the scale of data transmitted could be enormous. Alexander Hanff estimates that if 4GB were transmitted to hundreds of millions or billions of devices, the total data volume could reach several exabytes, with potential carbon emissions ranging from 6,000 to 60,000 tons of CO₂.
However, these figures are difficult to independently verify. For example, testing on two Windows 11 PCs a few years old showed that they were not download targets. This suggests that Google may only be deploying this model to relatively new devices, although the specific criteria are not publicly disclosed.
Formal complaint filed alleging violation of European law
Legally, Alexander Hanff has filed a formal complaint against Google. He argues that downloading large amounts of data to user devices without informing them or obtaining their consent violates the European Union's General Data Protection Regulation.
Google has not yet issued an official statement regarding these allegations.
