Sustainability of Digital Formats: Planning for Library of Congress Collections

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ID3 Metadata for MP3, Version 2

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name ID3 Metadata for MP3, Version 2

Structured data chunk containing descriptive metadata about the file to which it is generally pre-pended, virtually always an MP3_FF (MP3 sound file). Referred to by its creators as an "informal standard" for a "container format," ID3v2 permits the identification of title, artist, date, genre, and more. See Notes for more information.

Sub-versions are not separately described at this Web site at this time. The actual specifications are summarized in the Wikipedia article ID3 (consulted February 2007):

  • ID3v2.2: ". . . the first public version of ID3v2. . . . used three character frame identifiers rather than four (TT2 for the title instead of TIT2)."
  • ID3v2.3: ". . . expanded the frame identifier to four characters, and added a number of frames. A frame could contain multiple values, separated with a / character."
  • ID3v2.4: ". . . the latest version of the standard, dated November 1, 2000. Notably, it allows textual data to be encoded in UTF-8, which was a common practice in earlier tags despite the standard. It uses a null byte to separate multiple values, and so / can appear in text data again."

Addenda to the ID3v2.3 and ID3v2.4 standards have been published:

  • The ID3 Chapter (CHAP) and Table of Contents (CTOC) establishes a mechanism for podcasts, talking books, and the like that contain multiple tracks, stories, or other distinct audio entries in a single file, compatible with ID3v2.3 and ID3v2.4 tags. (2005)
  • The ID3 Accessibility Addendum makes ID3 metadata accessible to the visually impaired via a new Audiotext (ATXT) frame type, compatible with ID3v2.3 and ID3v2.4 tags. The addition of ATXT frames to an ID3 tag will allow compatible players to provide an audible description of the ID3 metadata. (2006)
Production phase Generally used for final-state, end-user delivery.
Relationship to other formats
    Subtype of ID3, ID3 Metadata for MP3
    Used by MP3_FF, MP3 file format

Local use Explanation of format description terms

LC experience or existing holdings See ID3
LC preference See ID3

Sustainability factors Explanation of format description terms

Disclosure Fully documented. Developed by Martin Nilsson and colleagues; see web site.
    Documentation Documentation and specifications for all subversions and addenda at the developer's page.
Adoption Very widely adopted for World Wide Web dissemination and playback on specialized devices.
    Licensing and patents None, except use of the copyrighted logo is licensed by Martin Nilsson at no cost.
Transparency See ID3
Self-documentation See ID3
External dependencies None
Technical protection considerations None

Quality and functionality factors Explanation of format description terms

Normal rendering Not applicable
Fidelity (high audio resolution) Not applicable
Multiple channels Not applicable
Support for user-defined sounds, samples, and patches Not applicable
Functionality beyond normal rendering Permits inclusion of binary elements like still images and can contain lyrics that may be music-synchronized for karaoke or other applications. Addenda listed in the Identification and description section above permit the marking of chapters, tables of contents, and aids to accessibility. See also the notes on the Addenda to the ID3v2.3 and ID3v2.4 in the Description section above.

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension Not applicable.   
Internet Media Type Not applicable.   
Magic numbers See note.  See 3DI marker information in Notes below.

Notes Explanation of format description terms


ID3v2 binary content is structured as "frames" just like MP3_ENC (MP3 audio encoding). Each frame can contain up to 16 MB; the entire chunk can be as much as 256 MB. Version 2 supports Unicode, has an "unsynchronization scheme" to prevent incompatible players from attempting to play the ID3 chunk, and supports "enciphered" information. See also sub-version information in Identification and description above.

When ID3 metadata is placed in a MP3_FF file, established conventions call for the use of the ID3 marker which consists of the string "3DI". For ID3v1, the marker is positioned 10 bytes preceding the metadata. For ID3v2 data, the marker is positioned in the first 3 bytes of the file when the metadata is pre-pended and 10 bytes from the end of a file when it is post-pended.


Format specifications Explanation of format description terms

Useful references


Last Updated: 08/10/2021