While I’m personally not a fan of autoplaying videos in my apps, some prefer to have this as a matter of convenience. That’s why we aren’t surprised Google is experimenting with this feature in its YouTube app. Videos will start to play when you scroll through the Home section but you don’t have to be worried about being startled by audio as these videos will play without sound but will have subtitles overlaid. And if you’re worried about this eating up your data, only one video will play automatically at a time and you have the option to turn this feature off or have it work only on Wi-Fi. It must be noted that this feature isn’t available to all users as YouTube is just testing the feature out. Whether they roll this out to all users is something we don’t know right now.
Source: Android Authority