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Ininformation and communications technology, amedia type,[1][2]content type[2][3] orMIME type[1][4][5] is a two-part identifier forfile formats andcontent formats. Their purpose is comparable tofilename extensions anduniform type identifiers, in that they identify the intended data format. They are mainly used by technologies underpinning theInternet, and also used onLinux desktop systems.
TheInternet Assigned Numbers Authority (IANA) is the official authority for the standardization and publication of these classifications. Media types were originally defined in Request for CommentsRFC 2045 (MIME) Part One: Format of Internet Message Bodies (Nov 1996) in November 1996 as a part of theMIME (Multipurpose Internet Mail Extensions) specification, for denoting type ofemail message content and attachments;[6] hence the original name,MIME type. Media types are also used by other internet protocols such asHTTP,[7] document file formats such asHTML,[8] and theXDG specifications implemented by Linuxdesktop environments,[5] for similar purposes.
Different internet standards or web standards bodies differ on the preferred term for this type of identifier.
TheIANA andIETF use the term "media type", and consider the term "MIME type" to be obsolete,[1] since media types have become used in contexts unrelated to email, such as HTTP. By contrast, theWHATWG continues to use the term "MIME type" and discourages use of the term "media type" as ambiguous, since it is used with a different meaning in connection with theCSS@media feature.[4]
TheHTTP response header for providing the media type isContent-Type.[2] TheW3C has usedContentType as anXML data-type name for a media type.[3]XDG specifications implemented by Linuxdesktop environments continue to use the term "MIME type".[5]
A media type consists of atype and asubtype, which is further structured into atree. A media type can optionally define asuffix andparameters:
mime-type=type"/"[tree"."]subtype["+"suffix]*[";"parameter];
As an example, an HTML file might be designatedtext/html; charset=UTF-8. In this example,text is the type,html is the subtype, andcharset=UTF-8 is an optional parameter indicating the character encoding.
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.[6]
The "type" part defines the broad use of the media type. As of November 1996, the registered types were:application,audio,image,message,multipart,text andvideo.[6] By July 2024, the registered types included the foregoing, plusfont,example,model, andhaptics.[1]
An unofficial top-level type in common use ischemical, used forchemical file formats.[9][10][11] In the context of Linuxdesktop environments, the unofficial top-level typesinode (inodes other than normal files, such asfilesystem directories,device files orsymbolic links),[12]x-content (removable media, such asx-content/image-dcf forDCF digital cameras),[13]package (package manager packages)[14] andx-office (generic categories ofoffice productivity software document)[14] are used.
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.
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 byIETF Standards Action for external registration and management by well-known permanent organizations (e.g. scientific societies).
The standards tree does not use any tree prefix. Examples aretext/javascript,image/png.[15]
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.
The vendor tree includes media types associated with publicly available products. It uses thevnd. tree prefix. Examples are: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.
The personal or vanity tree includes media types associated with non publicly available products or experimental media types. It uses theprs. tree prefix. Examples areaudio/prs.sid,image/prs.btif.
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 thex. tree prefix. Examples areapplication/x.foo,video/x.bar. Media types in this tree cannot be registered.
This type was originally defined in RFC 1590 (published in September 1993) using thex- orX- prefix. RFC 2048 (published in November 1996) introduced thex. prefix, but discouraged use of the unregistered tree, as new personal and vendor trees with relaxed registration requirements are now available. The current RFC 6838 (published in January 2013) maintains the same recommendation, but subtypes prefixed withx- orX- are no longer considered to be members of this tree.
Media types that have been widely deployed (with a subtype prefixed withx- orX-) 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.application/x-www-form-urlencoded is an example of a widely deployed type that ended up registered with thex- prefix.[16]
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.[15]
The+xml suffix has been defined since January 2001 (RFC 3023[17]), 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.[18]
From the IANA registry:[1]
application/jsonapplication/ld+json (JSON-LD)application/msword (.doc)application/pdfapplication/sqlapplication/vnd.api+jsonapplication/vnd.microsoft.portable-executable (.efi, .exe, .dll)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-urlencodedapplication/xmlapplication/zipapplication/zstd (.zst)audio/mpegaudio/oggimage/avifimage/jpeg (.jpg, .jpeg, .jfif, .pjpeg, .pjp)[19]image/pngimage/svg+xml (.svg)image/tiff (.tif)model/obj (.obj)multipart/form-datatext/plaintext/csstext/csvtext/htmltext/javascript(.js)text/xmlMailcap (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.
An associated file is themime.types file, which associates filename extensions with aMIME 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 asapplication/octet-stream, andmime.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.
Whenviewing a file, these two work together as follows:mime.types associates an extension with a MIME type, whilemailcap 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
 | This sectionis missing information about Netscape. Please expand the section to include this information. Further details may exist on thetalk page.(November 2019) |
The mime.types file dates toNetscape, where it used a different format;[20] it usedkey–value pairs and a comma-separated list of extensions, together with astandard 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
[RFC2046] specifies that Media Types (formerly known as MIME types) and Media Subtypes will be assigned and listed by the IANA.
HTTP uses media types [RFC2046] in the Content-Type (Section 8.3) and Accept (Section 12.5.1) header fields in order to provide open and extensible data typing and type negotiation.
ContentType: A media type, as per [RFC2045].
Standards are encouraged to consistently use the term MIME type to avoid confusion with the use ofmedia type as described inMedia Queries.