I recently learned that just about any video playing in Chrome and Firefox can be popped out to a picture-in-picture (PIP) player. A PIP player gives you a sidecar video player window that you can arrange and resize anywhere on your screen. It sits on top of other windows so that you can view it while working from other apps. This is useful if, for instance, you are working through a coding tutorial on youtube.
For most video players, you can right click on the video and the menu that appears will include a "Picture in Picture" option. Select that and the arrange the player to your liking.
Youtube overrides right-click. If you right-click, you'll see one menu of Youtube-specific options. Right-click a second time to open the standard browser menu which will include the PIP option.
I noticed while also testing this on Firefox, that they have a PIP icon that appears as a small overlay on the right side of the video player that you can click as well. This is useful because I found some site's video players were (inadvertently) preventing right-click.