Blocking Screenshot

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Block Screenshots in iOS

Browser integration (Encrypted-Media + Content-Protection)

Widevine L1 uses the TEE/TrustZone to decrypt into secure buffers and then tells the compositor not to read those buffers when another process (or the OS screen-shot service) asks. If the device lacks L1 hardware, it falls back to L3, lowers the resolution, or refuses playback.source

Test at: https://www.netflix.com/watch/80164785

EME (Encrypted-Media Extensions) invites a CDM (e.g., Widevine) into the render process.
The CDM checks the GPU driver's "secure overlay" capability.
Chrome/Edge/Firefox mark the tab as copy-protected. When you hit Print Screen or OBS hooks into D3D11, Chromium refuses to composite the protected layer, so you get black while the rest of the tab (controls, subtitles) is still visible. Stack Overflow