It's very rare for Android to play video in the background without YouTube red. But now the new beta Chrome has changed that. Now you can play the web video in the background. Even directly on YouTube.
In the Chrome Beta 54 version, if you play a video on a Web page and then close the browser, you will receive a notification of the video message you just played. This video will be automatically paused (presumably, when you try to exit from a website, you don't need to look at the ad again) of course you can also click to play from the beginning. Audio streams can still be played in the background. They don't stop because you shut down chrome.
According to Android police, the beta Chrome video playback feature is still available on YouTube, and it's really awesome to have wood. However, this service is likely to close in the near future if the background playback is joined by YouTube Red's paid feature. But for now, you can still enjoy the little benefits that beta Chrome brings