The biggest hope I had from macOS Sierra was Picture in Picture, but sadly, iTunes is basically the only thing supporting it.
Till, then, I'm stuck using Helium.
Helium : http://heliumfloats.com
Till, then, I'm stuck using Helium.
Helium : http://heliumfloats.com
Though, really, they could go even further: I use Fast User Switching to basically be two people: "home" me, and "work" me, who each use the same apps but logged into different accounts. (The OS manages this far better than the one-off multi-account features of apps do, I find.) But Fast User Switching isn't very convenient when you "are" both users. How about letting me intermingle the Spaces from two login sessions, so I can have a "Picture In Picture" Space from my own other account open on my desktop?
(If you're wondering, Screen Sharing doesn't allow you to connect to localhost. Even if you hack around that [which requires patching some bytes in a private framework], it's still a cruddy experience, especially concerning screen locking and display resolution. And, obviously, slow.)
Control-click/Right-click on a YouTube video – the first time around it'll show its private menu – then CLICK AGAIN on the video, which will bring up Safari's menu for videos including the Picture-in-Picture option: http://i.imgur.com/ekWnBQr.png
I'm sure some browser plugin can be created to add the controls to Youtube or all the other major HTML5 players.