New W3C API will standardize Picture-in-Picture (PiP) mode. It will allow websites to show a floating video popup outside the browser window. Chrome and Safari are already testing the new API. The feature is already available for Google Canary users, who can enable it right now by following these instructions. The Chrome team is currently planning an experiment to assess how the API will fare and will decide if to ship it at the end of the tests. The experiment will start when Chrome 68 reaches the Beta channel (currently scheduled for June 7, 2018)
Source: https://www.bleepingcomputer.com/news/software/chrome-tests-picture-in-picture-api-to-show-floating-video-popups-outside-the-browser/