Google Chrome silently pushes 4 GB Gemini Nano model

Google Chrome is silently installing a 4 GB AI model on users’ devices, according to a detailed report that traced the downloads on macOS and Windows. The file, called weights.bin, sits in an OptGuideOnDeviceModel directory and contains the weights for Gemini Nano, Google’s on-device large language model.

The report says Chrome does not ask for consent before placing the file on disk, does not surface it in the browser UI, and will re-download it if the user deletes it. The behavior affects Chrome features tied to Google’s AI push, including on-device scam detection and writing assistance tools.

The findings were published by a researcher who said they verified the behavior on a freshly created Apple Silicon Chrome profile on macOS. To confirm when the model arrived, the researcher used macOS filesystem event logs, which showed Chrome creating the model directory, unpacking the model, and moving it into place over a 14-minute window on 24 April 2026.

According to the report, Chrome’s own internal state also recorded the model version and hardware eligibility checks. The browser noted performance_class: 6 and vram_mb: 36864, which the researcher says shows Chrome assessed the machine’s hardware before pushing the model.

The report also says Chrome’s feature flags included OnDeviceModelBackgroundDownload, which triggers the background download, and ShowOnDeviceAiSettings, which enables the on-device AI settings page. The researcher argues that the install begins before the user has a settings screen where they could reject it.

The same report says GoogleUpdater had already downloaded a smaller control component that points Chrome to the model. Chrome then fetched the multi-gigabyte weights directly from Google’s CDN. The researcher says this happened on a profile that had received no keyboard or mouse input from a human.

Windows users have reported similar behavior for more than a year, but the new report says the macOS logs make the sequence easier to verify. The researcher says deleting the file does not solve the problem because Chrome downloads it again when the profile is eligible.

The report compares this to a similar issue it raised previously involving Anthropic and Claude Desktop, where software from one vendor wrote into another vendor’s browser installs without asking. In this case, the claim is that Chrome itself is writing a large AI model into the user’s profile without a prompt, while the browser’s visible AI features remain separate from the local model.

The report also says Chrome’s AI Mode omnibox pill is cloud-backed and does not use the local Gemini Nano model. That means users can end up with both the storage cost of a silent model download and a separate cloud AI interface that processes queries on Google’s servers.