Extension:CheckUser/Client Hints

Client hints are information about your device and browser which is sent on request to websites you visit by browsers such as Google Chrome and Edge. The CheckUser extension, which is used on sites such as Wikipedia, requests and collects this data by default to support the community in reducing vandalism and abuse. This data is deleted 90 days after it's collection and can only be viewed by trusted users.

Why is this data is collected?
Trusted users were previously able to use the user agent string to identify this information about your device and browser. This, along with IP addresses, were used to compare two user accounts to determine if they were being used by the same device. The comparison is performed on users where there is a suspicion of abusing multiple accounts, such as by evading blocks on other accounts.

However, the user agent string is being deprecated across many major browsers which makes it harder for these trusted users to compare abusive users. Client hints data contains the information that was previously held by the user agent string, and as such can complement the user agent string by providing the information it used to give.

What data is collected?
Client hints data contains similar information to what was provided in the user agent string. This information includes the brand and version information of your browser, the brand and version information of your operating system and whether the device is a mobile device. A more in-depth explanation of the technical side of client hints can be found at https://developer.mozilla.org/en-US/docs/Web/HTTP/Client_hints.

When is the data collected?
The client hints data is collected every time you make an edit or logged action. On some wikis, including Wikimedia wikis, this includes logging in and out of your account. The data is not collected when viewing pages or opening the edit form without then saving your changes.

When does the data get deleted?
The data is deleted after 90 days on Wikimedia wikis, including Wikipedia.

For non-Wikimedia wikis this may be different, as they may choose to keep this data for a longer or shorter time. The privacy policy should contain information on when this data is deleted.