Why Chrome Installs a 4GB Gemini Nano Model Without Your Consent (And How to Remove It)

Chrome version 147 began silently downloading the Gemini Nano model weights (about 4 GB) into a hidden folder ( %LOCALAPPDATA%\Google\Chrome\User Data\OptGuideOnDeviceModel on Windows or

~/Library/Application Support/Google/Chrome/OptGuideOnDeviceModel

on macOS). The file weights.bin stores the on‑device model used by several built‑in AI features.

The on‑device model powers functions such as “Help me write”, page summarization, smart paste, tab‑group suggestions, device‑side anti‑phishing detection, and the Prompt API, Summarizer, Writer, Rewriter interfaces. These features are optional and rarely triggered by most users, so the 4 GB download provides little benefit for the majority.

The “AI Mode” button added to the address bar is unrelated; it still sends queries to Google’s cloud services and does not rely on the local model.

Privacy‑wise, Chrome documentation states that Gemini Nano runs entirely locally and does not transmit queries. The real concern is the undisclosed download and the difficulty of disabling it.

To stop the download, both flags must be disabled:

Open chrome://flags and set optimization-guide-on-device-model to Disabled .

On the same page, set prompt-api-for-gemini-nano to Disabled .

Restart Chrome and delete the OptGuideOnDeviceModel folder.

On Windows, a persistent solution is to add a registry key under HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Google\Chrome named GenAILocalFoundationalModelSettings with a DWORD value of 1, then reboot. This prevents Chrome from re‑enabling the flags after an update.

macOS and Linux currently have no equivalent permanent method; users must repeat the flag check after major Chrome upgrades.

Other Chromium‑based browsers such as Edge, Vivaldi, and Brave do not include this Gemini Nano download.

Disabling the flags disables the associated AI features but leaves normal browsing, the address‑bar “AI Mode” button, and regular search results unaffected.