IANA Media Types Overview

IANA Media Types

• IANA (Internet Assigned Numbers Authority) manages media types
• Media types indicate the format of content transmitted over internet protocols
• Each media type consists of a top-level type and a subtype
• Media types can have parameters
• Example: text/html; charset=UTF-8
  • text is the top-level type
  • html is the subtype
• charset=UTF-8 is a parameter
• Media types were originally designed for email messaging

History

• Media types were introduced for email messaging
• Ned Freed and Nathaniel S. Borenstein defined media types in RFC 2046, November 1996
• Media types were also called MIME types, for values in the Content-Type MIME header

Usage

• Standards:
  • HTML
  • HTTP
  • MIME (Multipurpose Internet Mail Extensions)
• Applications:
  • Email clients
  • Web browsers
  • Search engines

Registration Procedure

• IANA is responsible for managing media type registration
• Website for IANA is https://www.iana.org/
• Media types are registered for media formats
• Ned Freed, John C. Klensin, and Tony Hansen specified and registered media types in RFC 6838, January 2013
• A list of all the media types is available at https://www.iana.org/assignments/media-types/media-types.xhtml

Top-level Type and Subtype Names

• Top-level and subtype names are case insensitive

Parameters (1)

• Parameter names are case insensitive
• Parameters can appear in any order
• It's an error to specify a parameter more than once
• No defined syntax for parameter values
• Parameter names, values, and meanings must be fully specified during registration

Parameters (2)

• Examples:
  • Content-Type: text/html; charset=UTF-8
  • Content-Type: audio/ogg; codecs=vorbis
  • Content-Type: video/ogg; codecs="theora, vorbis"
  • Content-Type: multipart/form-data; boundary=AaB03x
  • Content-Type: text/csv; charset=ISO-8859-1; header=present

Top-level Types

• application: Types for discrete data not fitting other types, particularly for processing by applications
• audio: Audio data
• font: Font formats
• image: Image formats
• message, multipart: Composite types for encapsulating multiple objects, each with separate media types
• model: Electronically exchangeable representations in a domain (e.g., 3D models)
• text: Many subtypes define a charset parameter
• video: Video data

Subtypes

• Each subtype is registered in a specific registration tree.
• The subtype name provides information about the corresponding tree.
• Subtype names starting with a specific prefix belong to that tree.

Registration Trees

• Standards tree: Intended for general interest types, no prefix in subtype name
• Vendor tree: For media types associated with publicly available products, subtype names begin with vnd. followed by the vendor and product name
• Personal or vanity tree: For non-commercially distributed or experimental types, subtype names begin with prs.
• Unregistered x. tree: For use in private, local environments, with agreement within the using parties; not recommended

Registration Trees (1): Standards Tree

• Intended for types of general interest to the internet community
• Subtypes in this tree do not have a prefix
• Examples: application/gzip, application/xml, audio/mp4, image/jpeg, multipart/mixed, text/csv, video/ogg

Registration Trees (2): Vendor Tree

• Used for media types related to publicly available products
• Subtypes start with vnd. followed by the vendor and product
• Examples: application/vnd.ms-excel, image/vnd.adobe.photoshop

Registration Trees (3): Personal or Vanity Tree

• Used for non-commercially distributed or experimental types
• Subtypes start with prs.
• Example: audio/prs.sid

Registration Trees (4): Unregistered x. Tree

• For types used in private, local environments
• Cannot be registered
• Discouraged in favor of vendor or personal trees

Structured Syntax Suffix

• The part of the subtype name after the '+' character (if present)
• Specifies the underlying structure (e.g., JSON or XML)
• Registered by IANA
• Examples of suffixes: +ber, +cbor, +cbor-seq, +der, +fastinfoset, +gzip, +json, +json-seq, +jwt, +sqlite3, +tlv, +wbxml, +zip, +zstd, +xml, +yaml

Registration Requirements

• Media type registrations can specify how applications should interpret fragment identifiers
• Structured syntax suffix registration can specify how applications should interpret fragment identifiers for media types using structured syntax

Notable Media Types (Examples)

• Various examples of media types across categories (application, audio, font, image, message, model, text, video, multipart) are listed with their respective formats and further information resources.

This quiz covers the essentials of IANA media types, including their structure, history, and usage in internet protocols. Learn about the significance of media types in applications such as email clients and web browsers, and understand the registration process by IANA. Test your knowledge of MIME types and their role in content transmission.