I believe it was originally just youtube, but it has support for a whole lot of services now including reddit, twitter, and much more. Looking at the file name

I believe it was originally just youtube, but it has support for a whole lot of services now including reddit, twitter, and much more. Looking at the file names here should give you a pretty good idea of what is supported. https://github.com/ytdl-org/youtube-dl/tree/master/youtube_dl/extractor https://github.com/ytdl-org/youtube-dl/tree/master/youtube_d...