Disappearing data: Google Chrome could be secretly downloading a 4GB file
Google is silently downloading a 4GB on-device AI model to computers running Google Chrome, allegedly without user consent or the option to decline the download.
Some users reported that the model caused performance issues and could only be temporarily deleted as it quietly redownloads itself in the background.
Computer scientist and privacy lawyer Alexander Hanff wrote about the situation after he found that Google had secretly downloaded the file onto his system.
“Google Chrome is reaching into users’ machines and writing a 4GB on-device AI model file to disk without asking,” Hanff wrote in his blog.
“It is the weights for Gemini Nano, Google’s on-device LLM. Chrome did not ask. Chrome does not surface it. If the user deletes it, Chrome redownloads it.”
Weights files contain the numerical parameters within a neural network that determine how a large language model (LLM) processes information. These files often take up a large amount space.
This specific file powered the features that Google marketed under names like “Help me write” as well as on-device scam detection and other AI-assisted browser functions.
The files are allegedly being downloaded to any machine with the Chrome web browser installed, whether on Windows or MacOS. It is unclear if Linux variants are affected.
Per Hanff, the download is triggered when Chrome’s AI features are active, and in the most recent versions of the browser, these features are activated by default.
“On any machine that meets the hardware requirements, Chrome treats the user’s hardware as a delivery target and writes the model,” he explained.
Hanff explained that MacOS keeps a filesystem event log that records every file created, modified or deleted at the OS level, independent of any application logging.
This record cannot be changed by applications and showed Hanff that, on 24 April 2026, Chrome created a directory on his PC named “OptGuideOnDeviceModel.”
Chrome then unpacked a file called “weights.bin” into the folder, along with other files and an execution config, all without receiving any human input.
“Total install time, from directory creation to final move: 14 minutes and 28 seconds. Total human action against the profile during that window: none,” he said.
South African users report a 4GB Google file installed on their systems
Hanff also confirmed that when a user deletes the weights file, Chrome redownloads it. The only way to disable the download is to turn off Chrome’s AI features in a hidden settings menu (chrome://flags).
For Windows users, one option is to use the Registry to change their software policies, which is risky and should not be attempted without due consideration.
At least three users in South Africa have confirmed to MyBroadband that the weights.bin file had been downloaded to their PCs.
A Mac user told us that the file was present on their system, but it was not the full 4GB file as reported by Windows users.
The majority of South African users we surveyed said that they did not have the file downloaded to their systems. It may be because they had not activated any of Chrome’s AI features.
Hanff alleged that the silent installation of the file was in direct breach of the European Union’s ePrivacy Directive and the GDPR. The main legal issue is the failure to obtain users’ consent.
That meant Google could also be in breach of the South African Protection of Personal Information Act (POPIA), as it shared many characteristics with GDPR.
Hanff argued that installing the on-device AI model could not be justified, even if it were used to store a user’s chats and AI-related information on the device.
However, he also found that pushing the “AI Mode” pill button in the browser omnibar did not use the on-device Gemini Nano model.
Instead, AI Mode was configured to send user queries to Google’s cloud-based LLMs as before, while the user paid for storage and bandwidth to download and install Gemini Nano.
MyBroadband reached out to Google representatives in South Africa and Google’s press office for confirmation about the silent install. Neither provided comment by publication.
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