The local file maintained by DJ software that stores all analyzed track data including BPM, key, cue points, and beatgrids.
A library database is the proprietary data store that DJ software maintains on the host computer to index a DJ's music collection and record all analysis results and prep work. It holds BPM, Camelot key, waveform data, beatgrid positions, cue points, loop markers, play count, rating, and organizational structure such as playlists or crates, separately from the audio files themselves.
Why it matters
Because all prep work lives in the database rather than the audio file, the database is effectively the DJ's most valuable asset after the music itself. Losing or corrupting the database without a backup means losing every cue point, beatgrid correction, and organizational decision accumulated over years of preparation.
In practice
Back up the database on a separate schedule from the audio files. In Rekordbox, use the built-in backup tool under Preferences to export a timestamped snapshot to an external drive. In Serato, the primary database lives in the _Serato_ folder inside your Music folder (~/Music/_Serato_ on macOS). Serato also creates a separate _Serato_ folder at the root of any external drive you have imported tracks from. Copy both the Music/_Serato_ folder and any drive-level _Serato_ folders alongside your music whenever you clone or migrate your library.
