For example Netflix doesn’t allow to take screenshots, and in discord if you try to screen share the window is black.
I’m sure that other sites do it as well.
In: Technology
I can answer this for protected video playback (like Netflix) in the Edge browser on Windows. It’s actually part of my day job, I work on the team that makes the video rendering pipeline for the Edge browser.
Lots of people are mentioning events that notify the browser so it can hide the content or saying that DRM prevents you from capturing it, but that is not actually what is at play here!
The images that make up your video are just travelling down a different “pipe” than the one that the screenshotting software is looking at.
It might seem odd, but the screenshot isn’t actually taken from your screen. The image is captured earlier in the process, before all the different “pipes” containing image data have converged. In the Netflix case, the video is sent to the screen via Direct Composition (DCOMP). The way this works is that we define an area of the screen where the video should be shown and we put nothing there, this is why it shows up as black in your screenshot. Then we tell your GPU exactly where this blank area is, and give it the video data so that it can put the video on your screen directly.
This process skips sending the images to the OS’s compositor (the thing that stitches all the images from the different pipes together), which is where the screenshotting software is getting it’s image from. This gives us some other benefits besides preventing easy recording of protected content, like significantly increased battery life.
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