IANA image format string from binary stream How can I get the official IANA Image Media Type (if any) of a binary stream? I'd like to avoid trusting to file extensions and vague guesses when handling images. Preferably some command using common tools like ImageMagick's `identify`, or some programming language if necessary.

You could use the `file` command. It's available on most linux distributions by default, and you can get it for Windows via the GnuWin32 file package.

Call it with:


$ file --mime-type clock.png
clock.png: image/png


Note that it's not 100% accurate - I don't think anything can be theoretically.

If you want to do that in code, there's `libmagic` that provides a C api. It can process either files or in-memory buffers. (`file` uses that on Linux.)