https://thenextweb.com/google/2018/06/29/youtube-makes-picture-in-picture-video-mostly-free-for-android-users-in-the-us/

Quite possibly the best thing about being a YouTube Red/Premium/Google Play Music subscriber is the ability to watch videos in a floating picture-in-picture (PiP) window on my phone. That allows me to continue watching a video while chatting, browsing the web, or doing pretty much any activity.

I’ll soon be losing that bragging right. YouTube is bringing PiP video to anyone on Android O within the US, whether you pay for YouTube Premium or not. The change was first spotted by XDA, though it’s since been confirmed in a Google support page.