ID3 is a metadata standard originally developed for MP3 files in the mid-1990s. It defines a container baked into the file itself that stores information about the audio: artist, title, album, track number, genre, BPM, key, cover art, comments, and custom fields. The standard has been extended and adopted by other formats since then, so the term "ID3 tags" is used loosely to refer to embedded audio metadata across formats.
Why DJs should care deeply about tags
Tags are the difference between a library and a pile of files. Here's why they matter:
- Tags travel with the file. Unlike a database entry that lives inside rekordbox or Serato, a tag is written into the file itself. Move the file, and the metadata moves with it.
- Well-tagged libraries are portable. Switching from Serato to rekordbox (or to anything else) is orders of magnitude less painful when your BPM, key, and genre data live in the files rather than in a proprietary database.
- Smart playlists and search depend entirely on tag quality. Searching for "dark techno" in a library where genre is blank everywhere returns nothing. Garbage in, garbage results.
A practical DJ tagging workflow
A common approach: download tracks, run them through Mixed in Key (or a similar analyzer) to auto-write BPM and Camelot key into the appropriate tag fields, then add custom tags for vibe, energy level, or intended usage context. The comments field or a custom "energy" field can hold values like "peak hour," "opener," or "peak-to-closing" — searchable in the booth when you need a specific tool for a specific moment.
Some DJ software writes metadata back to its own database rather than to the file. Rekordbox, for example, stores cue points and beat grids in its library database by default, not in the ID3 tags (though you can configure it to export some data to tags). If you uninstall rekordbox or your library database corrupts, those cue points are gone. Know where your data actually lives.
Standard fields DJs use
- BPM — beats per minute; written by analysis software and readable by DJ software for sync and sorting
- Key — tonal key, often written as a Camelot code (e.g., 8A) or standard notation (e.g., Am)
- Genre — searchable category; only as useful as how consistently you apply it
- Comment — a general-purpose text field; popular for energy ratings, personal notes, and workflow flags
- Grouping — sometimes used by DJs for set-context labeling
Format notes
ID3v2 (the current version) supports all the fields above and more. WAV files have historically had inconsistent ID3 support depending on the software — if portability matters, AIFF or MP3 tend to be safer bets for reliable tag read/write across applications. FLAC uses a different metadata system (Vorbis comments) but most DJ software reads it correctly.