Note the distinction between two types of js driven video playback that are possible. Those which require transcoding and those who can do with just transmuxing

Note the distinction between two types of js driven video playback that are possible. Those which require transcoding and those who can do with just transmuxing. HTML5 playback can only support few codecs but FLV can contain a wide variety of video and audio codecs. Flv.js does a great job of transmuxing h.264 frames in a different container, hence it only plays those flv which are h.264/aac. Transcoding can make it possible to even play HEVC or any non-standard codec on browser. This can be heavy on CPU especially hand-held devices. When using one of these in production you must understand that it is not very practical to do transcoding on the fly like this : https://strukturag.github.io/libde265.js/ https://strukturag.github.io/libde265.js/ . It is theoretically possible to play vp9 on an ios or a hevc on a pc but this will be impractical for low-cpu devices.