Picture-in-picture in the browser is a feature to let the user watch a video pop-out of a current tab and float it on top of other windows. This feature's been available in Google Chrome and Opera, just recently, Mozilla has brought it as a built-in feature for Windows with version 71 and macOS and Linux with version 72.
For Chrome users, picture-in-picture has been available as a built-in feature since version 70. Actually, you can enable this feature in two simple options, either use this built-in feature or install the Chrome extension.
If you use the extension, it’s an easier method even downloading the extension is an extra step. This extension adds a dedicated button next to the address bar that lets you reach it instantly by clicking on the icon to open a video in a picture-in-picture mode with a mini-player. You can also use the keyboard to enable as well by just pressing “Alt + P” on Windows or “Options key + P” on Mac.
Another option is using its built-in feature and it requires you to manually do a right-click on videos, but you have to do it two times continuously to get the mouse menu pop-out.
Firstly, just make sure whether you have Firefox version 71 for Windows and 72 for macOS and Linux but if not, you have to update your Firefox browser. Once your browser gets updated, you will see a small blue “Picture in picture” when you hover your mouse over it while the video starts playing on a page. Then it's really easy, you just click the button and the video will swap to picture-in-picture mode.
In default, picture-in-picture is enabled and you can turn it off or on by clicking "Enable picture-in-picture video controls" in its setting.
Among these three browsers, Opera may be the first browser to let you play a video in picture-in-picture mode. You can enable this feature by going to the Opera setting and you will see "Video pop-out". You can toggle it on or off, but it's enabled by default.
Opera's video pop-out feature is super easy to enable. The video will soon pop out over windows when you click on the "Clone" icon located on the top of the video.