Best general video download extension for Firefox imo. I've been using it for years now and it's been able to detect videos where other extensions might have failed to, and it caters to the widest array of formats that I've seen. Although it's a shame that some formats now require a desktop helper application to be installed, it runs incredibly smooth and is easy to use. The entire source code is also available so there's transparency in knowing that it isn't doing anything it's not supposed to.