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Media type

February 16, 2023

A media type (also known as a MIME type)[1] is a two-part identifier for file formats and format contents transmitted on the Internet. The Internet Assigned Numbers Authority (IANA) is the official authority for the standardization and publication of these classifications. Media types were originally defined in Request for Comments RFC 2045 (MIME) Part One: Format of Internet Message Bodies (Nov 1996) in November 1996 as a part of the MIME (Multipurpose Internet Mail Extensions) specification, for denoting type of email message content and attachments;[2] hence the original name, MIME type. Media types are also used by other internet protocols such as HTTP[3] and document file formats such as HTML,[4] for similar purposes.

Naming

A media type consists of a type and a subtype, which is further structured into a tree. A media type can optionally define a suffix and parameters:

type "/" [tree "."] subtype ["+" suffix]* [";" parameter]

As of November 1996, the registered types were: application, audio, image, message, multipart, text and video.[2] By December 2020, the registered types included the foregoing, plus font, example, and model.[5]

An unofficial top-level name in common use is chemical.[6][7][8]

As an example, an HTML file might be designated text/html; charset=UTF-8. In this example, text is the type, html is the subtype, and charset=UTF-8 is an optional parameter indicating the character encoding.

A subtype typically consists of a media format, but it may or must also contain other content, such as a tree prefix, producer, product or suffix, according to the different rules in registration trees.

Types, subtypes, and parameter names are case-insensitive. Parameter values are usually case-sensitive, but may be interpreted in a case-insensitive fashion depending on the intended use.[9]

Common examples [10]

  • application/javascript
  • application/json
  • application/ld+json
  • application/msword (.doc)
  • application/pdf
  • application/sql
  • application/vnd.api+json
  • application/vnd.ms-excel (.xls)
  • application/vnd.ms-powerpoint (.ppt)
  • application/vnd.oasis.opendocument.text (.odt)
  • application/vnd.openxmlformats-officedocument.presentationml.presentation (.pptx)
  • application/vnd.openxmlformats-officedocument.spreadsheetml.sheet (.xlsx)
  • application/vnd.openxmlformats-officedocument.wordprocessingml.document (.docx)
  • application/x-www-form-urlencoded
  • application/xml
  • application/zip
  • application/zstd (.zst)
  • audio/mpeg
  • audio/ogg
  • image/avif
  • image/jpeg (.jpg, .jpeg, .jfif, .pjpeg, .pjp) [11]
  • image/png
  • image/svg+xml (.svg)
  • model/obj (.obj)
  • multipart/form-data
  • text/plain
  • text/css
  • text/csv
  • text/html
  • text/xml

Registration trees

All media types should be registered using the IANA registration procedures. For the efficiency and flexibility of the media type registration process, different structures of subtypes can be registered in registration trees that are distinguished by the use of tree prefixes. Currently the following trees are created: standard (no prefix), vendor (vnd. prefix), personal or vanity (prs. prefix), unregistered (x. prefix). These registration trees were first defined in November 1996 (obsoleted RFC 2048 - currently RFC 6838). New registration trees may be created by IETF Standards Action for external registration and management by well-known permanent organizations (e.g. scientific societies).

Standards tree

The standards tree does not use any tree prefix:[12]

type "/" subtype ["+" suffix] *[";" parameter]

Examples: application/javascript, image/png.

Registrations in the standards tree must be either associated with IETF specifications approved directly by the IESG, or registered by an IANA recognized standards-related organization.

Vendor tree

The vendor tree includes media types associated with publicly available products. It uses the vnd. tree prefix:[12]

type "/" "vnd." subtype ["+" suffix] *[";" parameter]

Examples: application/vnd.ms-excel, application/vnd.oasis.opendocument.text.

The terms "vendor" and "producer" are considered equivalent in the context. Industry consortia as well as non-commercial entities can register media types in the vendor tree. A registration in the vendor tree may be created by anyone who needs to interchange files associated with some software product or set of products. However, the registration belongs to the vendor or organization producing the software that employs the type being registered, and that vendor or organization can at any time elect to assert ownership of a registration done by a third party.

Personal or vanity tree

The personal or vanity tree includes media types associated with non publicly available products or experimental media types. It uses the prs. tree prefix:

type "/" "prs." subtype ["+" suffix] *[";" parameter]

Examples: audio/prs.sid, image/prs.btif.

Unregistered tree

The unregistered tree includes media types intended exclusively for use in private environments and only with the active agreement of the parties exchanging them. It uses the x. tree prefix:

type "/" "x." subtype ["+" suffix] *[";" parameter]

Examples: application/x.foo, video/x.bar.

Media types in this tree cannot be registered. According to RFC 6838 (published in January 2013), any use of types in the unregistered tree is strongly discouraged. In addition, subtypes prefixed with x- or X- are no longer considered to be members of this tree.

According to obsoleted RFC 2048 (published in November 1996)—it should rarely, if ever, be necessary to use unregistered types, and as such use of any x., x- or X- prefixes is discouraged. Obsoleted RFC 1590 (published in September 1993) stated that the use of the x- or X- prefix may be used for unregistered subtypes.

Media types that have been widely deployed (with a subtype prefixed with x- or X-) without being registered, should be, if possible, re-registered with a proper prefixed subtype. If this is not possible, the media type can, after an approval by both the media types reviewer and the IESG, be registered in the standards tree with its unprefixed subtype.

Suffix

Suffix is an augmentation to the media type definition to additionally specify the underlying structure of that media type, allowing for generic processing based on that structure and independent of the exact type's particular semantics. Media types that make use of a named structured syntax should use the appropriate IANA registered "+"suffix for that structured syntax when they are registered. Unregistered suffixes should not be used (since January 2013). Structured syntax suffix registration procedures are defined in RFC 6838.[12]

The +xml suffix has been defined since January 2001 (RFC 3023[13]), and was formally included in the initial contents of the Structured Syntax Suffix Registry along with +json, +ber, +der, +fastinfoset, +wbxml, and +zip in January 2013 (RFC 6839). Subsequent additions include +gzip, +cbor, +json-seq, and +cbor-seq.[14]

Mailcap

Mailcap (derived from the phrase "mail capability") is a type of meta file used to configure how MIME-aware applications such as mail clients and web browsers render files of different MIME-types. The mailcap format is defined by RFC 1524 "A User Agent Configuration Mechanism for Multimedia Mail Format Information" but is not defined as an Internet standard. It is supported by most Unix systems.

Lines can be comments starting with the # character, or a mime-type followed by how to handle that mime type.

Mime.types

An associated file is the mime.types file, which associates filename extensions with a MIME type. If the MIME type is properly set, this is unnecessary, but MIME types may be incorrectly set, or set to a generic type such as application/octet-stream, and mime.types allows one to fall back on the extension in these cases. Similarly, since many file systems do not store MIME type information, but instead rely on the filename extension, a mime.types file is frequently used by web servers to determine MIME type.

When viewing a file, these two work together as follows: mime.types associates an extension with a MIME type, while mailcap associates a MIME type with a program.

In UNIX-type systems, the mime.types file is usually located at /etc/mime.types and/or $HOME/.mime.types and the format is simply that each line is a space-delimited list of a MIME type, followed by zero or more extensions. For example, the HTML type can be associated with the extensions .htm and .html by the following line: 

text/html htm html

Netscape use

The mime.types file dates to Netscape, where it used a different format;[15] it used key–value pairs and a comma-separated list of extensions, together with a standard header consisting of a specific comment that identifies the file as a mime.types file, as follows. 

#--Netscape Communications Corporation MIME Information # Do not delete the above line. It is used to identify the file type. type=text/html exts=htm,html

See also

References

  1. ^ "Media Types". IANA. IANA. 4 June 2018. Retrieved 5 June 2018.
  2. ^ a b Freed, N.; Borenstein, N. (November 1996). "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies". Internet Engineering Task Force. Retrieved 15 July 2015. {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ Nielsen, Henrik; Fielding, Roy T.; Berners-Lee, Tim (May 1996). "Hypertext Transfer Protocol -- HTTP/1.0". Retrieved 2 Feb 2017. {{cite journal}}: Cite journal requires |journal= (help)
  4. ^ "HTML 4.01 Specification". 24 Dec 1999. Retrieved 2 Feb 2017.
  5. ^ "Media Types". IANA. 2020-12-09. Retrieved 2020-12-15.
  6. ^ Daniel Leidert, Egon Willighagen (2007). . Archived from the original on 2016-10-08. Retrieved 2016-04-28.
  7. ^ "Chemical MIME Home page". 22 December 1998. Retrieved 11 May 2019.
  8. ^ S. Rzepa, Henry; Murray-Rust, Peter; J. Whitaker, Benjamin (14 August 1998). "The Application of Chemical Multipurpose Internet Mail Extensions (Chemical MIME) Internet Standards to Electronic Mail and World Wide Web Information Exchange". Journal of Chemical Information and Modeling. American Chemical Society. 38 (6): 976–982. doi:10.1021/ci9803233.
  9. ^ Freed, Ned; Borenstein, Nathaniel S. (November 1996). "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies". Retrieved 20 September 2018. {{cite journal}}: Cite journal requires |journal= (help)
  10. ^ "Media Types".
  11. ^ "MIME types (IANA media types) - HTTP | MDN".
  12. ^ a b c Freed, N. (January 2013). "Media Type Specifications and Registration Procedures". Ietf Request for Comments (RFC) Pages - Test. Internet Engineering Task Force (IETF). RFC6838. ISSN 2070-1721. Retrieved 15 July 2015.
  13. ^ Kohn <dan@dankohn.com>, Dan (January 2001). "XML Media Types". tools.ietf.org. Retrieved 2021-03-05.
  14. ^ "Structured Syntax Suffix Registry" (XML). IANA. 2012-07-20. Retrieved 2019-11-08.
  15. ^ WEBMASTERS: mime types Archived 2000-12-07 at archive.today, John McAnally, Thu, 22 Jan 1998 15:29:29 -0600 (CST)

External links

  • IANA list of official media types
  • The Python Standard Library | mailcap Mailcap file handling
  • Common MIME types from Mozilla MDN

February 16, 2023
media, type, this, article, confusing, unclear, readers, please, help, clarify, article, there, might, discussion, about, this, talk, page, july, 2018, learn, when, remove, this, template, message, media, type, also, known, mime, type, part, identifier, file, . This article may be confusing or unclear to readers Please help clarify the article There might be a discussion about this on the talk page July 2018 Learn how and when to remove this template message A media type also known as a MIME type 1 is a two part identifier for file formats and format contents transmitted on the Internet The Internet Assigned Numbers Authority IANA is the official authority for the standardization and publication of these classifications Media types were originally defined in Request for Comments RFC 2045 MIME Part One Format of Internet Message Bodies Nov 1996 in November 1996 as a part of the MIME Multipurpose Internet Mail Extensions specification for denoting type of email message content and attachments 2 hence the original name MIME type Media types are also used by other internet protocols such as HTTP 3 and document file formats such as HTML 4 for similar purposes Contents 1 Naming 1 1 Common examples 10 1 2 Registration trees 1 2 1 Standards tree 1 2 2 Vendor tree 1 2 3 Personal or vanity tree 1 2 4 Unregistered tree 1 3 Suffix 2 Mailcap 3 Mime types 3 1 Netscape use 4 See also 5 References 6 External linksNaming EditA media type consists of a type and a subtype which is further structured into a tree A media type can optionally define a suffix and parameters type tree subtype suffix parameter As of November 1996 the registered types were application audio image message multipart text and video 2 By December 2020 the registered types included the foregoing plus font example and model 5 An unofficial top level name in common use is chemical 6 7 8 As an example an HTML file might be designated text html charset UTF 8 In this example text is the type html is the subtype and charset UTF 8 is an optional parameter indicating the character encoding A subtype typically consists of a media format but it may or must also contain other content such as a tree prefix producer product or suffix according to the different rules in registration trees Types subtypes and parameter names are case insensitive Parameter values are usually case sensitive but may be interpreted in a case insensitive fashion depending on the intended use 9 Common examples 10 Edit application javascript application json application ld json application msword doc application pdf application sql application vnd api json application vnd ms excel xls application vnd ms powerpoint ppt application vnd oasis opendocument text odt application vnd openxmlformats officedocument presentationml presentation pptx application vnd openxmlformats officedocument spreadsheetml sheet xlsx application vnd openxmlformats officedocument wordprocessingml document docx application x www form urlencoded application xml application zip application zstd zst audio mpeg audio ogg image avif image jpeg jpg jpeg jfif pjpeg pjp 11 image png image svg xml svg model obj obj multipart form data text plain text css text csv text html text xmlRegistration trees Edit All media types should be registered using the IANA registration procedures For the efficiency and flexibility of the media type registration process different structures of subtypes can be registered in registration trees that are distinguished by the use of tree prefixes Currently the following trees are created standard no prefix vendor vnd prefix personal or vanity prs prefix unregistered x prefix These registration trees were first defined in November 1996 obsoleted RFC 2048 currently RFC 6838 New registration trees may be created by IETF Standards Action for external registration and management by well known permanent organizations e g scientific societies Standards tree Edit The standards tree does not use any tree prefix 12 type subtype suffix parameter Examples application javascript image png Registrations in the standards tree must be either associated with IETF specifications approved directly by the IESG or registered by an IANA recognized standards related organization Vendor tree Edit The vendor tree includes media types associated with publicly available products It uses the vnd tree prefix 12 type vnd subtype suffix parameter Examples application vnd ms excel application vnd oasis opendocument text The terms vendor and producer are considered equivalent in the context Industry consortia as well as non commercial entities can register media types in the vendor tree A registration in the vendor tree may be created by anyone who needs to interchange files associated with some software product or set of products However the registration belongs to the vendor or organization producing the software that employs the type being registered and that vendor or organization can at any time elect to assert ownership of a registration done by a third party Personal or vanity tree Edit The personal or vanity tree includes media types associated with non publicly available products or experimental media types It uses the prs tree prefix type prs subtype suffix parameter Examples audio prs sid image prs btif Unregistered tree Edit The unregistered tree includes media types intended exclusively for use in private environments and only with the active agreement of the parties exchanging them It uses the x tree prefix type x subtype suffix parameter Examples application x foo video x bar Media types in this tree cannot be registered According to RFC 6838 published in January 2013 any use of types in the unregistered tree is strongly discouraged In addition subtypes prefixed with x or X are no longer considered to be members of this tree According to obsoleted RFC 2048 published in November 1996 it should rarely if ever be necessary to use unregistered types and as such use of any x x or X prefixes is discouraged Obsoleted RFC 1590 published in September 1993 stated that the use of the x or X prefix may be used for unregistered subtypes Media types that have been widely deployed with a subtype prefixed with x or X without being registered should be if possible re registered with a proper prefixed subtype If this is not possible the media type can after an approval by both the media types reviewer and the IESG be registered in the standards tree with its unprefixed subtype Suffix Edit Suffix is an augmentation to the media type definition to additionally specify the underlying structure of that media type allowing for generic processing based on that structure and independent of the exact type s particular semantics Media types that make use of a named structured syntax should use the appropriate IANA registered suffix for that structured syntax when they are registered Unregistered suffixes should not be used since January 2013 Structured syntax suffix registration procedures are defined in RFC 6838 12 The xml suffix has been defined since January 2001 RFC 3023 13 and was formally included in the initial contents of the Structured Syntax Suffix Registry along with json ber der fastinfoset wbxml and zip in January 2013 RFC 6839 Subsequent additions include gzip cbor json seq and cbor seq 14 Mailcap EditMailcap derived from the phrase mail capability is a type of meta file used to configure how MIME aware applications such as mail clients and web browsers render files of different MIME types The mailcap format is defined by RFC 1524 A User Agent Configuration Mechanism for Multimedia Mail Format Information but is not defined as an Internet standard It is supported by most Unix systems Lines can be comments starting with the character or a mime type followed by how to handle that mime type Mime types EditAn associated file is the mime types file which associates filename extensions with a MIME type If the MIME type is properly set this is unnecessary but MIME types may be incorrectly set or set to a generic type such as application octet stream and mime types allows one to fall back on the extension in these cases Similarly since many file systems do not store MIME type information but instead rely on the filename extension a mime types file is frequently used by web servers to determine MIME type When viewing a file these two work together as follows mime types associates an extension with a MIME type while a href Mailcap html class mw redirect title Mailcap mailcap a associates a MIME type with a program In UNIX type systems the mime types file is usually located at etc b mime types b and or HOME b mime types b and the format is simply that each line is a space delimited list of a MIME type followed by zero or more extensions For example the HTML type can be associated with the extensions htm and html by the following line text html htm html Netscape use Edit The mime types file dates to Netscape where it used a different format 15 it used key value pairs and a comma separated list of extensions together with a standard header consisting of a specific comment that identifies the file as a mime types file as follows Netscape Communications Corporation MIME Information Do not delete the above line It is used to identify the file type type text html exts htm html This article is missing information about Please expand the article to include this information Further details may exist on the talk page November 2019 See also EditContent negotiation Content sniffing XML and MIME Filename extensionReferences Edit Media Types IANA IANA 4 June 2018 Retrieved 5 June 2018 a b Freed N Borenstein N November 1996 Multipurpose Internet Mail Extensions MIME Part One Format of Internet Message Bodies Internet Engineering Task Force Retrieved 15 July 2015 a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help Nielsen Henrik Fielding Roy T Berners Lee Tim May 1996 Hypertext Transfer Protocol HTTP 1 0 Retrieved 2 Feb 2017 a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help HTML 4 01 Specification 24 Dec 1999 Retrieved 2 Feb 2017 Media Types IANA 2020 12 09 Retrieved 2020 12 15 Daniel Leidert Egon Willighagen 2007 The chemical mime data project Archived from the original on 2016 10 08 Retrieved 2016 04 28 Chemical MIME Home page 22 December 1998 Retrieved 11 May 2019 S Rzepa Henry Murray Rust Peter J Whitaker Benjamin 14 August 1998 The Application of Chemical Multipurpose Internet Mail Extensions Chemical MIME Internet Standards to Electronic Mail and World Wide Web Information Exchange Journal of Chemical Information and Modeling American Chemical Society 38 6 976 982 doi 10 1021 ci9803233 Freed Ned Borenstein Nathaniel S November 1996 Multipurpose Internet Mail Extensions MIME Part One Format of Internet Message Bodies Retrieved 20 September 2018 a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help Media Types MIME types IANA media types HTTP MDN a b c Freed N January 2013 Media Type Specifications and Registration Procedures Ietf Request for Comments RFC Pages Test Internet Engineering Task Force IETF RFC6838 ISSN 2070 1721 Retrieved 15 July 2015 Kohn lt dan dankohn com gt Dan January 2001 XML Media Types tools ietf org Retrieved 2021 03 05 Structured Syntax Suffix Registry XML IANA 2012 07 20 Retrieved 2019 11 08 WEBMASTERS mime types Archived 2000 12 07 at archive today John McAnally Thu 22 Jan 1998 15 29 29 0600 CST External links EditIANA list of official media types The Python Standard Library mailcap Mailcap file handling Common MIME types from Mozilla MDN Retrieved from https en wikipedia org w index php title Media type amp oldid 1135649358, wikipedia, wiki, book, books, library,

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