The method for turning off autoplay on iOS, Android, and other mobile YouTube incarnations is pretty straightforward because the toggle itself is, relatively, front and center. To disable the function, simply load a video, then look for the “Autoplay” toggle, as highlighted in the image below. The toggle looks the same and is located in the same place on both iOS and Android.
If you do not see this toggle on your mobile YouTube app, then the app most likely needs to be updated. In one rare case on one of our devices, we didn’t see the toggle until we completely uninstalled the app (despite updating it) and then reinstalled it.
As a small aside for readers who found their way to this article searching for a way to halt autoplaying video on the Apple TV (which uses the YouTube App for tvOS, a branch of iOS)–you won’t find an on-screen toggle like you do with the mobile apps, but you can turn autoplay off by launching the YouTube app on your Apple TV and looking in Settings > Autoplay.