YouTube, as a rule, doesn’t let you play videos in the background. If you exit the app and/or lock your screen, it stops playing and there isn’t anything you can do about it. If you’ve jailbroken your device then there is probably a Cydia tweak that lets you play YouTube in the background. The alternative for users who do not jailbreak is to use third-party apps that let you play YouTube in the background. The thing is, all this is unnecessary. If you’re willing to inconvenience yourself with a third-party app, you can just use Safari, Chrome, or Firefox and YouTube’s mobile interface to the same effect.
Open the browser on your iOS device. This trick works with Chrome, Firefox, and Safari. Visit YouTube and look for the video you want to play in the background. Tap it so that it starts playing. Make sure the video enters the player mode and that you don’t leave it at the buffering screen.
Press the home button to return to your home screen. Swipe up to bring up the Control Center and swipe left to go to the media controls. The media controls will show you the video you were just playing in your browser. Tap the Play button to start playing the video.
You can lock your screen and the video will continue to play. The one caveat with this trick is that even if you’re playing a playlist, YouTube will not automatically start playing the next video. You will need to unlock your device and play the video manually.
The lock screen will show the same controls it does when you play music in the stock Music app. It’s highly unlikely you’ll get any ‘album/cover art’ but the video will play nevertheless. YouTube’s mobile interface is almost as good as the app itself; you can sign in to your account and access your history. Essentially, you don’t miss any real features that the YouTube app has to offer but you can now play YouTube in the background without installing anything extra.