I know some of us linux users use SMPlayer not just for movies but also for watching YouTube videos on it. If you watch just one or two videos a day, that’s fine, but if you watch everything through it, it can be tedious to copy every single link, then open SMPlayer and open the “add link” function. About a year ago or so I discovered this cool extension which is intended primarily for browsers only but in reality it can be used for any program, probably even for PC games, altough I haven’t tried that yet. :) The extension’s name is “Open With” and it does exactly what the name suggests - opens a page with another application that can accept URL addresses. It sends the address to another application which is what makes it perfect to watch videos with your favorite video player. All you need to do is install the extension, open its settings and follow the instruction there to make it work. It’s best if you put the python file inside ~/.mozilla, so that you don’t have to worry about the file ever being moved somewhere else. The extension is supposed to work on both Linux and Windows but I’ve never been able to make it work on Windows. After that it’s pretty simple - click “Add browser”, navigate to smplayer.desktop or vlc.desktop in /usr/share/applications (local applications also works, if you have placed a .desktop file there), navigate to the icon for your video player and that’s it! Now you can open YouTube in Firefox, right click on any video and select “Open With” --------> your video player.