This app/add on is fantastic. I am an engineering student who has ALOT of online lectures to go through. I HAVE to download all of them, every class builds on the next. The videos come from alot of media, this extension is the only one that has successfully downloaded all the media from the various sources. It is much better than sketchier tools that i have used. The only time it CANT work is when the media uploads through a third party popup, ie blackboard collaborate. But no app I know of can.