ID3

The MP3 standard did not include a method for storing file metadata. In 1996 Eric Kemp had the idea to add a small chunk of data to the audio file, thus solving the problem. The method, now known as ID3v1, quickly became the de facto standard for storing metadata in MP3s.[4]

The ID3v1 tag occupies 128 bytes, beginning with the string TAG 128 bytes from the end of the file. The tag was placed at the end of the file to maintain compatibility with older media players. If a player does not recognize the tag it would play a small burst of static instead of ignoring it. This tag allows 30 bytes each for the title, artist, album, and a "comment", four bytes for the year, and a byte to identify the genre of the song from a predefined list of 80 values (Winamp later extended this list to 148 values).

One improvement to ID3v1 was made by Michael Mutschler in 1997. Since the comment field was too small to write anything useful, he decided to trim it by two bytes and use those two bytes to store the track number. Such tags are referred to as ID3v1.1.[4]

In 1998, a new specification called ID3v2 was created by multiple contributors.[10] Although it bears the name ID3, its structure is very different from ID3v1.

ID3v2 tags are of variable size, and usually occur at the start of the file, which aids streaming media as the metadata is essentially available as soon as the file starts streaming instead of requiring the entire file to be read first as is the case with ID3v1. ID3v2 tags consist of a number of frames, each of which contains a piece of metadata. For example, the TIT2 frame contains the title, and the WOAR frame contains the URL of the artist's website. Frames can be up to 16 MB in length, while total tag size is limited to 256MB. The internationalization problem was solved by allowing the encoding of strings not only in ISO-8859-1, but also in Unicode. Textual frames are marked with an encoding byte.[11]

There are 83 types of frames declared in the ID3v2.4 specification,[12] and applications can also define their own types. There are standard frames for containing cover art, BPM, copyright and license, lyrics, and arbitrary text and URL data, as well as other things.

There are three versions of ID3v2:

ID3v2.2 was the first public version of ID3v2. It used three character frame identifiers rather than four (TT2 for the title instead of TIT2). Most of the common v2.3 and v2.4 frames have direct analogues in v2.2. It is now considered obsolete.[13]

ID3v2.3 expanded the frame identifier to four characters, and added a number of frames. This is the most widely used version of ID3v2 tags, and is widely supported by Windows Explorer and Windows Media Player.[14]

ID3v2.4 was published on November 1, 2000. It allows text frames to contain multiple values, separated with a null byte. Textual data to be encoded in UTF-8 rather than UTF-16. Another new feature allows the addition of a tag to the end of the file before other tags (like ID3v1).[15]

ID3 tags may be edited in a variety of ways. On some platforms the file's properties may be edited by viewing extended information in the file manager. Additionally most audio players allow editing single or groups of files. Editing groups of files is often referred to as "batch tagging". There are also specialized applications, called taggers, which concentrate specifically on editing the tags and related tasks.

ID3 tags were designed with MP3 in mind, so they would work without problems with MP3 and MP3Pro files. However, the tagsets are an independent part of the MP3 file and can be used elsewhere. In practice, the only other formats that widely use ID3v2 tags are AIFF and WAV. In AIFF, the tag is stored inside an IFF chunk named "ID3". Windows media ASF files (WMA, WMV) have their own tagging formats but also support ID3 Tags embedded as attributes.[18]

MP4 also allows the embedding of an ID3 tag.[19]

• CD-Text
• Vorbis comment
• Standard Architecture for Universal Comment Extensions (SAUCE)
• XBin (eXtended Binary)

• Official website
• List of genres in ID3v1
• ID3v1 Specification
• Side-by-side Comparison of ID3 Versions and Frames
• ID3 TAG and Enhanced TAG specification at the Wayback Machine (archived 10 March 2012)