14 DAY TRIAL // Playing YouTube videos in the background is not allowed on mobile phones because Google is offering such functionality as part of YouTube Red, which is only available for a fee in select markets.
In other words, if you were planning to let YouTube run in the background so you can listen to a podcast or music mix while on the go with the phone locked, that’s not possible without more complex tweaks like rooting on Android and jailbreaking on iPhone.
And yet, it looks like iOS 11.3 re-enables YouTube background playing on iPhone, which means that Apple users can do all of the above once again, even though this is very unlikely to be the expected behavior. This means Google is very likely to patch this with the next YouTube app update, so enjoy it while you still can.
Google expected to patch it
Reddit users explain in this discussion thread that it’s technically enough to open a YouTube video in Safari and then lock the phone to have the content run in the background. Others, however, say that you first need to go to the home screen before locking the phone, otherwise the video is automatically paused.
Some explain that resuming playback from the Control Center also does the magic, but all methods appear to rely on the same bug/feature that came with iOS 11.3.
There’s no report of such functionality on devices running a previous version of iOS, so you have to update your device should you want to play YouTube videos when the iPhone is locked.
Without a doubt, the loophole will be patched sooner or later, so alternatives will continue to be very popular. While third-party YouTube clients offering such capabilities have been pulled from the App Store, there still are apps which somehow offer background playback support for Google’s video-sharing site, including Dolphin browser.