I never signed up for Firefox sync, but firefox would pick up the youtube history from one of my laptops and sync on my other laptop, which I don't desire.

hi tiburonhyundai, if you're logged in to the same google accounts on both devices, google/youtube might collect and merge your viewing history on both those devices. in order to clear and stop that please refer to those two links: https://www.youtube.com/feed/history https://www.eff.org/de/deeplinks/2012/02/how-remove-your-youtube-viewing-and-search-history-googles-new-privacy-policy