Chrome installed 4 GB of AI on your machine and quietly removed the line that promised your data would stay put

Five words vanished from a Chrome menu. Those five words said that your data was not leaving your computer. At the same moment, 4 GB of artificial intelligence were quietly arriving on a billion machines.

The line that is no longer there

On Chrome 147, the Settings > System > On-device AI option read: "To power features like scam detection, Chrome can use AI models that run directly on your device without sending your data to Google servers. When this is off, these features might not work."

On Chrome 148, rolled out in early April 2026, the same menu now reads: "Chrome can use AI models that run directly on your device. When this is off, these features might not work."

Five words removed: without sending your data to Google servers. The Register and Decrypt independently confirmed the diff by comparing the two builds on the same machine.

Asked by both outlets, Google answers the same sentence: "This doesn't reflect a change to how we handle on-device AI for Chrome. The data that is passed to the model is processed solely on device." Translation: nothing changes on the technical side. But the written guarantee, that one is gone from the interface.

Four gigs of AI, with no ask

Around the same time, privacy researcher Alexander Hanff publishes his forensic write-up. He set up a clean audit machine on April 23, fresh Chrome 148.0.7778.97, no extensions.

On April 24 at 16:38 Paris time, a folder called OptGuideOnDeviceModel appears inside the Chrome User Data directory. Fourteen minutes later, at 16:53, it contains a four-gigabyte weights.bin file. No pop-up, no notification, no interaction.

That file is Gemini Nano. Google's on-device LLM, shipped through Chrome since 2024 according to the company. It powers scam detection, the "Help me write" feature in text fields, page summaries, and an API that web developers can call from their own sites to talk to the local model.

A detail also flagged by Digital Trends: Chrome's most visible AI feature, the AI mode inside the address bar, does not use that local model. It sends your query to Google's cloud. So you store 4 GB locally for features you probably do not use, while the one you might use still hits the servers.

The landlord and the missing clause

Picture your landlord quietly removing the clause where they promised not to enter without warning, while keeping the spare keys. They do not announce they will rummage through your drawers. They simply erased their written promise. Removing the guarantee takes away a textual obstacle, it is not proof of a betrayal already committed.

Hanff, who knows European regulation well, points at article 5(3) of the 2002 ePrivacy directive. It forbids storing information on a user's terminal equipment without prior, free, specific, informed and unambiguous consent, unless strictly necessary for a service the user explicitly requested. Storing 4 GB of an LLM whose features were not explicitly requested by the end user is uncomfortable legal ground.

Parisa Tabriz, VP and GM of Chrome, went public to defend the feature, calling it "core to our developer & security strategy". Digital Trends notes she did not address two specific points: the question of consent, and the fact that if you manually delete the folder, Chrome quietly re-downloads it on next launch.

What you can check on your machine

Type chrome://on-device-internals/ in Chrome's address bar, open the Model Status tab. If Gemini Nano runs on your machine, you will see the model name, its version (typically v3Nano), its disk size (around 4072 MiB) and the backend in use. You can also open Chrome's Task Manager (Shift+Esc) to see if an Optimization Guide On Device Model process is active.

The actual file lives here:

• macOS: ~/Library/Application Support/Google/Chrome/OptGuideOnDeviceModel
• Windows: %LOCALAPPDATA%\Google\Chrome\User Data\OptGuideOnDeviceModel

Delete the folder by hand and Chrome will restore it on next launch. That is exactly the point Tabriz did not address.

How to actually turn it off

Three documented methods, from the simplest to the most permanent.

Settings. Go to Settings, then System, then turn off the On-device AI toggle. According to Android Authority, this toggle is not yet visible for every user, the rollout is partial.

Flags. If the toggle is missing, open chrome://flags, look up optimization-guide-on-device-model, set it to Disabled. Then look up prompt-api-for-gemini-nano and do the same. Restart Chrome. You can then delete the OptGuideOnDeviceModel folder without it coming back.

The radical option, Windows only. In the registry, under HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Google\Chrome, create a DWORD called GenAILocalFoundationalModelSettings set to 1. Chrome stops downloading these models for good. Meant for admins managing a fleet of machines.

What the diff actually says

The story you will hear this week is "Chrome silently installed Gemini Nano". That story is true, and it was already true before April.

The new piece is not the download itself, it is what came with it: the written guarantee that data does not leave the machine has been removed from the only place the user could read it. Not from a technical changelog. From the settings panel, the exact spot you visit when you want to understand what is running on your device.

Nothing proves Chrome is exfiltrating anything today. Google's legal position holds as long as the data is processed locally. What changed is that we can no longer point at an official Google sentence saying "we commit in writing to not sending anything to servers". That sentence used to exist. It does not anymore. And the timing of the removal lines up exactly with a one-billion-device rollout.

You can still disable Gemini Nano. It is just that you have to know where to look, and that information will not be handed to you on its own.