Watch YouTube videos at full window (not full screen)

I use a large 27" iMac which I divide up windows with a browser in the top right of the screen. One thing that often frustrated me is that I could not maximise a video to fill the window completely. I had to fill my entire screen or watch it in the embedded size.

It turns out this is not too hard, change the URL in the browser from https://www.youtube.com/watch?v=oHg5SJYRHA0 to https://www.youtube.com/embed/oHg5SJYRHA0