Security researcher Alexander Hanff recently discovered that the Google Chrome browser downloads a large AI model to users' devices without explicit notification. According to Tom's Hardware, the files appear in a folder named OptGuideOnDeviceModel; its largest file is weights.bin, which Hanff says contains the Gemini Nano model. The download is roughly 4 GB in size.
Which devices are affected and how the installation behaves
Hanff's analysis indicates the model is placed on any device that meets the minimum hardware requirements for running it. The behavior was observed on both Windows and macOS. Chrome reportedly does not prompt the user for permission before installing the model, nor is there an obvious user-facing option to block or remove the files automatically.
Users can locate the files in Chrome's installer directory and delete them manually, but Hanff reports that when Chrome is restarted the 4 GB package is downloaded again.
Google's response
A Google spokesperson told Gizmodo that a simplified version of Gemini Nano has been available to users since 2024, and that the model performs important security-related tasks such as fraud detection. The spokesperson said the model requires some device storage but will be automatically removed if insufficient space is available to run it.
Google also said it began rolling out a toggle in February that allows users to disable the model's operation and updates.
Is the installation documented?
Google did not deny that the components are installed on users' devices, but the company did not prominently announce the downloads. There is a passing reference in the Google Chrome Terms of Service to the ongoing development of technologies and features — including use of AI and machine learning to improve services and block malicious content — but the language does not explicitly mention an automatic download of a roughly 4 GB local model.
Why this matters
Automatically placing multi-gigabyte files on user devices raises issues around storage management and user transparency: an unannounced installation can surprise users, particularly on devices with limited disk space. Google says there are protections (such as automatic removal when storage is insufficient) and that a user-facing disable switch has started to roll out, but the discovery highlights questions about how service providers handle local AI components and how clearly they communicate those actions to users.
Conclusion
Alexander Hanff's finding shows that Google Chrome downloads an approximately 4 GB OptGuideOnDeviceModel/weights.bin file without notification to Windows and macOS devices; the files can be manually deleted but are re-downloaded on Chrome restart. Google confirms a simplified Gemini Nano exists and has been available since 2024, and says a disable switch began rolling out in February to let users turn off the model and its updates.
