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. Some players would play a small burst of static when they read the tag, but most ignored it, and almost all modern players will correctly skip 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.[13] 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 16MB 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.[14]

$00 – ISO-8859-1 (LATIN-1, Identical to ASCII for values smaller than 0x80).
$01 – UCS-2 encoded Unicode with BOM, in ID3v2.2 and ID3v2.3.
$02 – UTF-16BE encoded Unicode without BOM, in ID3v2.4.
$03 – UTF-8 encoded Unicode, in ID3v2.4.

However, mojibake is still common when using local encodings instead of Unicode. In particular, some Japanese editors are known to use Shift JIS encoding, which usually has disastrous effects: it will not work with any standard-compliant software regardless of local settings (since it is not supported by the standard), will not work outside Japan (since Shift JIS has very little support outside Japan), and will not even work on all Japanese computers even with a specifically non-compliant reader (as it is software-dependent and settings-dependent).

There are 83 types of frames declared in the ID3v2.4 specification,[15] 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

v2.2 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. Now this standard is considered obsolete.[16]

ID3v2.3

v2.3 expanded the frame identifier to four characters, and added a number of frames. This is the most widely used version of ID3v2 tags.[17]

ID3v2.4

v2.4 was published on November 1, 2000, and remains the latest version. A major new addition is that a text frame can contain multiple values, separated with a null byte. It also allows textual data to be encoded in UTF-8 rather than UTF-16, which was a common practice in some parts of the world in earlier tags (despite the standard, since it was not supported yet) because UTF-8 typically encodes Asian scripts less efficiently than UTF-16. Another new feature allows the addition of a tag to the end of the file before other tags (like ID3v1).[18]

No version of Windows Explorer or Windows Media Player—up to and including Windows 10 (initial release) and WMP 12, respectively—interprets ID3v2.4 tags correctly. These programs can interpret ID3v2.3 and earlier, however.[19][20] Windows Explorer finally supports reading ID3v2.4 tags with the Windows 10 Creators Update (version 1703), but the new Windows 10 version still cannot interpret the ID3v2.4 tag correctly with some of non-English and Asian characters.

Windows Media Player 9 Series | 255 | 0

$00     Other
$01     32x32 pixels 'file icon' (PNG only)
$02     Other file icon
$03     Cover (front)
$04     Cover (back)
$05     Leaflet page
$06     Media (e.g. label side of CD)
$07     Lead artist/lead performer/soloist
$08     Artist/performer
$09     Conductor
$0A     Band/Orchestra
$0B     Composer
$0C     Lyricist/text writer
$0D     Recording Location
$0E     During recording
$0F     During performance
$10     Movie/video screen capture
$11     A bright coloured fish
$12     Illustration
$13     Band/artist logotype
$14     Publisher/Studio logotype

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. Some, such as puddletag offer advanced features such as advanced batch tagging or editing based on regular expressions.

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 should be usable elsewhere. In practice, the only other formats which widely uses 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.[24]

MP4 also allows the embedding of an ID3 tag.[25]

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

• Official website
• List of genres in ID3v1
• ID3v1 Specification
• ID3 TAG and Enhanced TAG specification at the Wayback Machine (archived 10 March 2012)
• TagLib at GitHub
• Side-by-side Comparison of ID3 Versions and Frames at the Wayback Machine (archived 20 June 2012)
• Online ID3 Tag Editor