If you you want to clear your entire watch history or search history, follow these steps:
- In your YouTube app, tap on the profile picture or icon on the right top of the screen
- Tap on Settings from the pop-up menu
- Tap on History & Privacy to continue
- You will have several options there such as Clear watch history, Clear search history, etc.
- You may also Pause watch and or search history from there.
- Refer to the screenshot below for all available options:

How to use YouTube in Incognito mode on Android?
As of 2020, you can also use incognito mode for temporarily not remembering history. This will help you to open a temporary YouTube session.
- In your YouTube app, tap on the profile picture or icon on the right top of the screen
- tap on Turn on Incognito from the pop-up menu
I hope this information is helpful!