You can remove videos from your YouTube history and then they won't influence the recommendations you get.

Recent product improvements have also made this process really easy.

There is an incognito mode within YouTube by clicking your profile picture and “turn on incognito”

Also available on mobile.

Works great with Premium.

On my iPhone, selecting this option brings the ads straight back, unfortunately.

I think this is only available on mobile, actually. I don't see this option on desktop.

> I very often open videos in private tabs so it doesn't destroy my recommendations

+1, I thought you were talking about me :)

in youtube history settings you can turn off history recording while you binge on trash content, and if you forget, you can remove it from the list in history. the setting persists across sessions and devices. note that this is different from the incognito setting which does turn ads back on...

I do this to keep my recommendations clean.

Can you do this on a mobile device like an ipad? Can you do this when not logged in?

If you log in to YouTube it does.