One disadvantage is that this forces less technical users to learn about technical details of media, which itself can get very complex. For example you seem to

One disadvantage is that this forces less technical users to learn about technical details of media, which itself can get very complex. For example you seem to know your way with the solutions you propose, but I already see an issue, as in reality WebM is a format limited to VP8 and VP9, and cannot contain H.264 video. But Chrome ignored this limitation and wrote a muxer that is actually able to store H.264 inside WebM files, thus going out of spec... which means different tools might have different degrees of support for those files. https://bugs.chromium.org/p/chromium/issues/detail?id=980822 https://bugs.chromium.org/p/chromium/issues/detail?id=980822 Arguably, a former user of YouTube or Vimeo shouldn't have to learn about all this, and shouldn't have to end up reading bug reports such as that one (and this is just scratching the can of worms that is all the topic of codecs, encodings, containers, etc.)