The Free On-line Dictionary of Computing (30 December 2018):

MIME type

    The unique identifier used
   for different file types when conveyed across a MIME-based
   protocol such as MIME e-mail or HTTP.

   Registration of MIME types is explained in RFC 2048.

   Official MIME types

(ftp://ftp.isi.edu/in-notes/iana/assignments/media-types/media-types).

   (1998-02-10)