https://www.cnbc.com/2018/07/10/how-to-watch-youtube-videos-incognito-mode.html

Google recently rolled out a new YouTube feature that lets you watch videos privately on your phone. That means you can watch content without Google keeping track, sort of like the private mode in your web browser.

It also means the app won't store your viewing history. If you hand your phone to a son or daughter, for example, you can put your phone in incognito mode so YouTube doesn't start recommending younger-skewing content to you.