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I wonder how zoom determines if a screenshot is taken.

On Linux/Wayland at least, there's no API for an app to determine that this is happening. So they'd have to show the watermark all the time.

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Yes as I understand the watermark is on the Zoom video stream you're viewing, so it doesn't need to detect when you take a local screenshot.

Likely by detecting certain keystrokes (that's what Snapchat does on iOS for example). Idk if there are other ways on macOS or Windows.

There is an API on iOS: UIApplicationUserDidTakeScreenshotNotification

https://developer.apple.com/documentation/uikit/uiapplicatio...

I was not aware of this- thank you!

Definitely not on Linux. Global hotkeys are managed by the compositor and can't be spied on by applications. There's also no API no read keystrokes from external apps. This is actually a security feature.

AFAIK, on iOS, the app is actually sent an event by the OS when a screenshot is captured.

You might be specifically talking about Wayland here then, but with X on the other hand, it's not difficult for example [0]

[0] https://security.stackexchange.com/questions/170596/is-it-po...

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