How to get YouTube in a pop-out screen

Sometimes you want to browse other tabs but keep watching YouTube in the background.
This apparently disappeared with HTML5 but it's still there on OS X High Sierra.
  1. All you need to do is right-click on a video (a black menu appears)
  2. and then right-click press again (now a grey menu appears).
  3. Select 'Enter Picture in Picture' and the video will pop-out to the top right (can be repositioned & resized).
Return using the on-screen icons. Map