With most file types these days containing format identification either through their file extension, some sort of metadata, or a format header (or all of the above), are MIME types still necessary?
Do modern browsers even care? Do servers?
If you have a dynamically-created resource that can change type (e.g. a dynamically-created image that can be either a jpg or a png), but want to put it at a known-in-advance URL, it is useful because the URL can’t contain a reliable file extension. I think that modern browsers do care about mime types and will only resort to guessing from the extension if it is unspecified or obviously wrong.
Also, the one that is forever trapped in an invisible box is an apt metaphor for the constraints of outdated social mores in modern society, just to get that out of the way.
Absolutely. We develop custom applications and use web servers as a transmission method for data. Without mime types we couldn’t define our custom file type handling on the web server.
They are absolutely relevant for anyone doing web application work.
They’re also quite relevant if you want need to include binary data in a text file, which happens more often than you’d expect.