Does anyone know of any productivity apps that help you do stuff when you've got multiple tabs open at once?

I'm at the point now where, I'll open my browser, click back to the tab that I need to watch, then click back to the tab I'm working on, open a new tab, click back to the old tab, and back to the new one. <br><br>I was trying to work on a sheet for work, but needed to watch a presentation on YouTube at the same time. I think it would be helpful to be able to actually watch the video right next to your work, or have it floating somewhere on the screen that's not in the way, but still viewable. <br><br>Does anyone know of an app like that? Ideally on the Mac, but I do use windows as well at my work computer.