What are MIME Types and Subtypes?

Last updated: September 5, 2017

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• MIME: Multipurpose Internet Mail Extensions

  MIME type information is used by server and browser to communicate about the type of file being transferred, and how it should be handled by the browser and helper applications. There is a good introduction to the topic on Wikipedia: http://en.wikipedia.org/wiki/MIME

  The Internet Assigned Numbers Authority (IANA) ( http://www.iana.org) keeps a list (http://www.iana.org/assignments/media-types/) of the MIME types which it has approved.

  Some types which have not been approved are nevertheless widely used because they are supported by various browsers. Mozilla, for example, maintains documentation on some of the "Plugins" ("Add-ons", "Extensions") used with its browsers: http://developer.mozilla.org/en/docs/Plugins. (Note the caution that plugins are a "legacy technology".) See also https://en.wikipedia.org/wiki/Plug-in_%28computing%29, https://en.wikipedia.org/wiki/NPAPI, and https://en.wikipedia.org/wiki/Google_Native_Client

• The Top-Level MIME Types and Some Subtypes

  • TEXT - Textual information.
    The Mime type/subtype "text/plain" normally applies to files with a ".txt" extension. HyperText Markup Language files are "text/html".

  • IMAGE - Image data.
    Common types are "image/gif" (Graphics Interchange Format), "image/tiff" (Tag Image File Format), and "image/jpeg" (Joint Photographic Experts Group, at http://www.jpeg.org).

  • AUDIO - Audio data.
    Files with the ".au" (from Sun) extension are normally of MIME type "audio/basic". Files with the ".wav" (from Microsoft) extension have the unofficial type "audio/x-wav". Files with the ".aif" (from Apple) extension have the unofficial type "audio/x-aiff". RealAudio (".ram") files have the unofficial type "audio/x-pn-realaudio".

  • VIDEO - Video data.
    Common subtypes are "quicktime" (".mov" extension, from Apple) and "mpeg" (.mp4) (Moving Picture Expert Group, at http://www.chiariglione.org/mpeg/ officially, with additional information at https://en.wikipedia.org/wiki/Moving_Picture_Experts_Group). Files with the ".avi" (from Microsoft) extension have the unofficial type "video/x-msvideo".

  • APPLICATION - Some other kind of data to be processed by an application.
    Common subtypes are "postscript", "pdf", "msword" and "zip".

  • MESSAGE - Message information.

  • MODEL - For multidimensional structures.

  • MULTIPART - For messages with multiple sections.

w02t3_1_mime Copyright © 2017 John N. Davis