Comment by bingo-bongo

5 days ago

You can use whatever name you like and the “x-“ indicates it’s experimental.

An RFC exists that discourages the “x-“ naming, but it’s still very much in use in the wild.

Yeah, but I mean I made a search for it and it's a non official MIME type but OC did not make it up in the comment. It seems to be in sparing use.