https://www.theverge.com/2018/5/8/17330269/youtube-picture-in-picture-mode-without-red-subscription-android-oreo

YouTube is reportedly testing picture-in-picture mode for users who don’t have a Red subscription, as spotted by Android Police. Picture-in-picture mode was first introduced in Android Oreo, and allows users to watch a video in a corner of the phone’s screen while simultaneously using another app. The feature allows you to multitask, so you could for example, search for take away food in another app while still watching a trailer for Infinity War.

YouTube previously restricted picture-in-picture mode to Red subscribers (which costs $9.99 a month), but it looks like the video service is expanding that feature to those without a subscription. Some Reddit users without Red memberships found that picture-in-picture worked for some content they tested, but not for music videos. (YouTube does say that picture-in-picture mode featuring music content is only available for Red subscribers.) As Android Police notes, the limited rollout seems to be controlled on the server side (aka, you can’t trigger it yourself), and YouTube has likely given content owners the ability to restrict picture-in-picture mode on their videos.