I have YouTube search and watch history turned off. Yet if I watch a video that someone sent me a link to, I will still get that exact video or others related to it in my recommendations afterwards. Normally, only videos that I explicitly save (by upvoting or subscribing to a channel) should alter my recommendations, but clearly Google is still saving something.

Huh. Since it sounds like you do vote on videos and subscribe to channels, is it possible Google is actually just making (correct) predictions based on that?

I'm just surprised because it really does work for me. But, I make a point of never voting/subscribing/commenting/queuing/etc. And the difference between when I'm logged out and logged in is very stark.

The videos I'm thinking of that someone sent to me are way outside of what I would normally watch, so seeing that exact video in recommendations and other videos from the same channel immediately afterwards on the home page can't be a coincidence. But most of the time what I watch doesn't affect recommendations, only the odd time.

In addition to curating what I want to see with upvotes/subscriptions, I also use the "Not interested" and "Don't recommend channel" buttons heavily. For some reason YouTube always recommends those stupid "meditation music" videos, even though I have never watched one and I always block those channels. Honestly, YouTube's recommendation engine is shite; even when I tell them exactly what I like, it still recommends absolute tripe, and most of what I discover comes from external (personal) recommendations.

I think they cache everything which was recommended for some time, haven't tested the exact period.

Actually, YouTube tracks your likes/dislikes data in a different way and it needs some obscure method to disable the privacy option. I don't remember the link though

What do you mean? I want Google to remember my ↑likes and subscriptions, so they can give me recommendations that actually reflect my preferences. I just don't want them to track which videos I watch or search for.

You can pause those in the settings under watch and search history. My problem is after I like a video or two, YouTube starts recommending me the same video over and over again. Or very similar videos. I'd rather have just a clean-slate experience.

I have turned off search amd watch history; see my previous comments.

If it starts recommending the same videos to me I press the Not Interestes button.