For new access, I need to be using WhatsApp Web on version 0.3.2041. If you are using an older version, you should clear your browser's cache and then restart it. You also need to have the latest app update on your mobile phone. This done, you can now watch a video from YouTube, Facebook or Instagram without clicking on the link. For a friend to be able to use the feature, it is important to wait a few seconds before sending the link before WhatsApp can load the thumbnail.
Through the floating window, the user can pause, play, move the video through the conversation, activate full screen mode, control the volume and open the original URL if necessary. To close, simply click the "x" in the upper left corner. Picture-in-Picture mode also works on WhatsApp Web with natively uploaded videos.