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Media type

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An Internet media type,[1] originally called a MIME type after MIME (Multipurpose Internet Mail Extensions) and sometimes a Content-type after the name of a header in several protocols whose value is such a type, is a two-part identifier for file formats on the Internet. The identifiers were originally defined in RFC 2046 for use in e-mail sent through SMTP, but their use has expanded to other protocols such as HTTP, RTP and SIP.

A media type is composed of at least two parts: a type, a subtype, and one or more optional parameters. For example, subtypes of text type have an optional charset parameter that can be included to indicate the character encoding, and subtypes of multipart type often define a boundary between parts.

Types or subtypes that begin with x- are nonstandard[2] (they are not registered with IANA). Subtypes that begin with vnd. are vendor-specific; subtypes in the personal or vanity tree begin with prs..[3]

MIME is short for Multipurpose Internet Mail Extensions, a specification for formatting non-ASCII messages so that they can be sent over the Internet. Many e-mail clients now support MIME, which enables them to send and receive graphics, audio, and video files via the Internet mail system.

There are many predefined MIME types, such as GIF graphics files and PostScript files. It is also possible to define your own MIME types.

In addition to e-mail applications, Web browsers also support various MIME types. This enables the browser to display or output files that are not in HTML format.

MIME was defined in 1992 by the Internet Engineering Task Force (IETF). A new version, called S/MIME, supports encrypted messages.

List of common media types

IANA manages a registry of media types and character encodings. The organization makes a list available to the public through the Web. Some of the more notable media types used on the Web are listed below:

  • Type application: Multipurpose files
    • application/EDI-X12: EDI X12 data; Defined in RFC 1767
    • application/EDIFACT: EDI EDIFACT data; Defined in RFC 1767
    • application/json: JavaScript Object Notation JSON; Defined in RFC 4627
    • application/javascript: JavaScript; Defined in RFC 4329 but not accepted in IE 8 or earlier
    • application/octet-stream: Arbitrary binary data[4]. Generally speaking this type identifies files that are not associated with a specific application. Contrary to past assumptions by software packages such as Apache this is not a type that should be applied to unknown files. In such a case, a server or application should not indicate a content type, as it may be incorrect, but rather, should omit the type in order to allow the recipient to guess the type.[5]
    • application/ogg: Ogg, a multimedia bitstream container format; Defined in RFC 5334
    • application/pdf: Portable Document Format, PDF has been in use for document exchange on the Internet since 1993; Defined in RFC 3778
    • application/soap+xml: SOAP; Defined by RFC 3902
    • application/xhtml+xml: XHTML; Defined by RFC 3236
    • application/xml-dtd: DTD files; Defined by RFC 3023
    • application/zip: ZIP archive files; Registered[6]
  • Type audio: Audio
  • Type image
  • Type message
    • message/http
  • Type model: 3D models
  • Type multipart: Archives and other objects made of more than one part
    • multipart/mixed: MIME E-mail; Defined in RFC 2045 and RFC 2046
    • multipart/alternative: MIME E-mail; Defined in RFC 2045 and RFC 2046
    • multipart/related: MIME E-mail; Defined in RFC 2387 and used by MHTML (HTML mail)
    • multipart/form-data: MIME Webform; Defined in RFC 2388
    • multipart/signed: Defined in RFC 1847
    • multipart/encrypted: Defined in RFC 1847
  • Type text: Human-readable text and source code
    • text/css: Cascading Style Sheets; Defined in RFC 2318
    • text/csv: Comma-separated values; Defined in RFC 4180
    • text/html: HTML; Defined in RFC 2854
    • text/javascript (Obsolete): JavaScript; Defined in and obsoleted by RFC 4329 in order to discourage its usage in favor of application/javascript. However, text/javascript is allowed in HTML 4 and 5 and, unlike application/javascript, has cross-browser support
    • text/plain: Textual data; Defined in RFC 2046 and RFC 3676
    • text/xml: Extensible Markup Language; Defined in RFC 3023
  • Type video: Video
  • Type vnd: Vendor Specific Files
  • Type x-pkcs: PKCS standard files
    • application/x-pkcs12: p12 files
    • application/x-pkcs12: pfx files
    • application/x-pkcs7-certificates: p7b files
    • application/x-pkcs7-certificates: spc files
    • application/x-pkcs7-certreqresp: p7r files
    • application/x-pkcs7-mime: p7c files
    • application/x-pkcs7-mime: p7m files
    • application/x-pkcs7-signature: p7s files

See also

References

  1. ^ "Internet Media Type registration, consistency of use". W3C. 2002-06-03. Retrieved 2006-11-29.
  2. ^ Freed, N. and Borenstein, N. (1996). "RFC 2045 - Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies". IETF. Retrieved 2006-11-29. {{cite web}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  3. ^ Freed, N.; Klensin, J. (2005). "RFC 4288 - Media Type Specifications and Registration Procedures". IETF. Retrieved 2008-06-14. {{cite web}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  4. ^ http://tools.ietf.org/html/rfc2046
  5. ^ http://www.w3.org/Protocols/rfc2616/rfc2616-sec7.html#sec7.2.1
  6. ^ http://www.iana.org/assignments/media-types/application/zip
  7. ^ http://www.iana.org/assignments/media-types/image/png
  8. ^ http://www.iana.org/assignments/media-types/image/vnd.microsoft.icon
  9. ^ http://www.iana.org/assignments/media-types/video/quicktime
  10. ^ http://www.iana.org/assignments/media-types/application/vnd.oasis.opendocument.text
  11. ^ http://www.iana.org/assignments/media-types/application/vnd.oasis.opendocument.spreadsheet
  12. ^ http://www.iana.org/assignments/media-types/application/vnd.oasis.opendocument.presentation
  13. ^ http://www.iana.org/assignments/media-types/application/vnd.oasis.opendocument.graphics
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