Comment by amiga386

File extension shouldn't matter at all, because data should have associated metadata (e.g. HTTP content-type, CSS image-set, HTML <video><source type=""/></video>)

> It’d be useful to know if you can read the file by looking only at its extension

That would be madness, and there's already a workaround - the filename itself.

For most people, all that matters is an MKV file is a video file, and your configured player for this format is VLC. Only in a small number of cases does it matter about an "inner" format, or choice of parameter - e.g. for videos, what video codec or audio codec is in use, what the bitrate is, what the frame dimensions are.

For where it _matters_, people write "inner" file formats in the filename, e.g. "Gone With The Wind (1939) 1080p BluRay x265 HEVC FLAC GOONiES.mkv", to let prospective downloaders choose what to download from many competing encodings of exactly the same media, on websites where a filename is the _only_ place to write that metadata (if it were a website not standardised around making files available and searching only by filenames, it could just write it in the link description and filename wouldn't matter at all)

Most people don't care, for example, that their Word document is A4 landscape, so much that they need to know _in the filename_.