Double-Tap the Sides of the Screen to Go Forward or Backward to YouTube
Android: Instead of the old-fashioned rewind button, video players have opted for skip buttons that allow you to go back or forward a bit. YouTube on Android has picked up this bandwagon with the latest update.
Now in the YouTube app, you can double-tap the left or right side of the screen to go forward or backward ten seconds. According to Android Police, this feature has been included in Google’s roadmap since 2015, but it has only been enabled selectively for some users on certain devices. However, Google finally made it official in the latest YouTube update, announcing it in the patch notes.
YouTube | Google Play Store via Android Police