A field of meta-data in MP3 and MP3pro audio files. The tags describe the contents, including song title, artist, album, year, comment, CD track and genre. ID3 tags are used for searching as well as displaying the title being played. In many cases, ID3 tags are not filled in or are erroneous, and an "ID3 tagger" utility, also called an "audio tagger" or "MP3 tagger," can be used to update them. Other than MP3 Although often erroneously called ID3 tags, other audio files (AAC, WMA, Ogg Vorbis, etc.) have their own meta-data tag format, but hold the same kinds of data. See music search and MusicBrainz. Why Were Song Titles Missing? CDs followed phonograph records, which contained nothing but sound waves "carved" into the vinyl platters. Reserving a few thousand bytes for the names of the album, artist and songs when there were 650 million available on the disc might seem obvious, but nobody envisioned playing music on the computer, and digital displays on CD players were expensive back then. Therefore, track number and length were the only meta-data in a CD until more descriptive fields (tags) were added later (see CD Text). ID3 Format Version 2 of the format (ID3v2) supports variable-length fields that hold titles of any length as well as the album cover image. The tags are at the beginning of the file so that song information can be displayed at the start for streaming audio. The original version of the format located the data in the last 128 bytes of the file and was limited to 30-byte text fields, a 4-byte year and 1-byte genre (80 categories). Version 1.1 (ID3v1.1) added CD track number. For more information, visit www.id3.org. See music CD identification, music search, metadata and streaming audio.