How to use Picture in Picture (Mini View) mode in Windows 10

Solution 1:

With the release of Windows 10 version 1703 (a.k.a. the Creators Update) in April 2017, native Picture-in-Picture capability was made available with the Mini View feature in the Movies & TV app:

Here’s how it works:

Launch the Movies & TV app and click a movie, trailer, or TV show to start playing it. Click the “Play in mini view” button in the bottom right-hand corner...

...and the “Leave mini view” button when you want to exit.

The mini view will stay on top of any other windows you have open. You can click and drag to move it around your screen, or click a corner and drag to resize the window.

(Source: Windows 10 Tip: Watch a video while using another app with mini view)

Solution 2:

Opera Browser has the ability to pop out most HTML5 players. It pops out over the top over everything also not just Opera.

Edit* Also if it's netflix, the netflix app on the windows store has the ability to use the built in picture in picture mode.