By default, Picture-in-Picture videos on macOS Sierra are docked in one of the four corners of your Mac’s display. If you try to move the window elsewhere, it will quickly snap back to one of the four default corners. This is very similar to how Picture-in-Picture mode works on the iPad.
But it’s also possible to dock videos anywhere on your display by using a handy keyboard combination. Watch our brief hands-on video for the quick how-to.
How to dock Picture-in-Picture videos anywhere on macOS Sierra
Step 1: Invoke a Picture-in-Picture video.
Step 2: While holding the Command (⌘) key, drag the Picture-in-Picture window to your desired location.
Step 3: Release the cursor while continuing to hold the Command (⌘) key.
Step 4: Release the Command (⌘) key after the overlay appears, and the video should stay locked in place.