Most likely this is caused by Firefox sending YouTube some YouTube or Google cookies that were previously set when you access your work/college account. One option is to flush those cookies, but doing that every time would be a huge pain. So here are some other suggestions: (1) Use a private window for your personal account Private windows use a separate cookie jar than your regular windows. (2) Experiment with container tabs More information in this article: [[How to use Firefox containers]]. Because you need to use Google/YouTube both for work/college and for personal, you can't force the sites to always open in one container, you'll need to open the sites manually in the container. (3) Consider creating a personal profile A profile is a settings folder, similar to a person/profile in Chrome (or identity in Internet Explorer, if you ever used that). Each profile has its own unique settings, but if you connect a new profile to your Firefox Account, then they will Sync and share personal data. Cookies will not Sync, so you can have two nearly identical Firefox profiles that sites see as different. It's a bit more of a hassle to start up alternate profiles, so I'll hold off on providing "how to" details for now. Ref. [[Profile Manager - Create, remove or switch Firefox profiles]]