Internet media type

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

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 have an optional charset parameter that can be included to indicate the character encoding (E.g.: text/html; charset=UTF-8), and subtypes of multipart type often define a boundary between parts. Allowed charset values are defined in the list of IANA character sets.

Types or subtypes that begin with x- are non-standard[2] (they are not registered with IANA). Subtypes that begin with vnd. are vendor-specific;[3] subtypes in the personal or vanity tree begin with prs.[4]. New media types can be created with the procedures outlined in RFC 4288.

The original name MIME type referred to the fact that the these types were used to identify non-ASCII parts of email messages composed using the MIME (Multipurpose Internet Mail Extensions) specification. Without MIME types, email clients would not be able to understand if an attachment files was a PNG file or a spreadsheet and would not be able to show them in the appropriate way.

In addition to email clients, web browsers also support various media types. This enables the browser to display or output files that are not in HTML format. Media type specification is also an important information for search engines for the classification of data files on the web.

There are many registered media types, such as GIF graphics files and PostScript files. It is also possible to define custom media types.

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 are listed below:

Type application

For Multipurpose files:

Type audio

For Audio.

Type image

Type message

Type model

For 3D models.

Type multipart

For archives and other objects made of more than one part.

Type text

For human-readable text and source code.

Type video

For video.

List of common media subtype prefixes

Prefix vnd

For vendor-specific files.

Prefix x

For non-standard files.

Prefix x-pkcs

For PKCS standard files.

See also

References

  1. ^ "Internet Media Type registration, consistency of use". W3C. 2002-09-04. http://www.w3.org/2001/tag/2002/0129-mime. Retrieved 2012-02-29. 
  2. ^ Freed, N. and Borenstein, N. (November 1996). "RFC 2045 - Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies". IETF. http://tools.ietf.org/html/rfc2045#section-5. Retrieved 2006-11-29. 
  3. ^ Freed, N.; Klensin, J.; Postel, J. (November 1996). "RFC 2048 - Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures, Section 2.1.2 - Vendor Tree". IETF. http://tools.ietf.org/html/rfc2048#section-2.1.2. Retrieved 2011-12-05. 
  4. ^ Freed, N.; Klensin, J. (December 2005). "RFC 4288 - Media Type Specifications and Registration Procedures". IETF. http://tools.ietf.org/html/rfc4288#section-3.2. Retrieved 2008-06-14. 
  5. ^ RFC 2046 - Multipurpose Internet Mail Extensions (MIME) Part Two: Media types. Tools.ietf.org. Retrieved on 2010-09-29.
  6. ^ HTTP/1.1: Entity. W3.org. Retrieved on 2010-09-29.
  7. ^ MIME SUBTYPE NAME: zip
  8. ^ MIME SUBTYPE NAME: png
  9. ^ MIME subtype name : Vendor Tree - vnd.microsoft.icon
  10. ^ Quicktime
  11. ^ vnd.oasis.opendocument.text
  12. ^ vnd.oasis.opendocument.spreadsheet
  13. ^ vnd.oasis.opendocument.presentation
  14. ^ vnd.oasis.opendocument.graphics
  15. ^ "Application Media Types". IANA. http://www.iana.org/assignments/media-types/application/index.html. Retrieved 2012-02-19. 

External links