With Picture in Picture, you can play a video in a movable window that “floats” on top of everything else, so you can always see it, no matter what you’re doing.
Play a web video with Picture in Picture
In Safari on your Mac, navigate to the web video you want to play.
Click and hold the Audio button in the Smart Search field or in a tab.
Choose Enter Picture in Picture. You can drag the window to any corner of the screen and the window stays put, even if you switch desktop spaces. You can resize the window to see more or less of what’s behind it.