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Comment by livinglist | Hacker News Reader

I remember there’s an app in China that has a QR code on screen all the time that is basically invisible to users unless you tune the color scale in a certain way, I forgot what it was for specifically but I imagine it was for tracking the screenshots taken and uploaded by users.

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WoW was spotted doing that in 2012. It contained information like the server IP, the account ID, and a timestamp. As far as I know, Blizzard has never commented on it, but one theory is that it's for troubleshooting purposes when a player reports a problem and includes a screenshot.

Xbox 360 home screen had a design of rings which served more than just design asthetics. They were for fingerprinting the Xbox incase of defects or even leaked screenshots

Looks like the iPhone one is only physically on the glass so wouldn't affect screenshots (unless you were photographing it with a very high resolution camera device).

> According to the report, the bar codes are engraved on the iPhone’s glass at different stages of manufacturing. [...] These codes are described as being “the size of a grain of sand” and, unsurprisingly, can only be seen with special equipment.

I've worked in companies where bug reports were typically very light on useful information but fairly often included a screenshot. By putting some key information (ideally a request ID, but a session ID or user ID can be invaluable) into the screenshot it can greatly increase the ability to solve these support queries quickly with little user friction.

IIRC in our case the data was encrypted so it couldn't be used for tracking outside of the support system. I do see how it can be considered harmful to add information that the user didn't intend to share but it also had clear user benefits (as well as company benefits of course).

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