The file format is how a piece of music is stored: how much of the original recording is kept, how much space it takes up, and whether your software can read it at all. For a DJ it matters in two places, how a track holds up on a real sound system and whether it loads when you need it.
Formats fall into three groups.
Compressed, lossy
Smaller files, with some audio information permanently discarded. Lossy encoders throw away detail based on what the ear is least likely to miss, which is why a good encoder at a high bitrate is very hard to tell apart from the original.
- MP3 - the most widely compatible format there is, and still the default of the scene. Common bitrates run from 192 to 320 kbps. For playing out, use 320.
- AAC (.m4a) - generally better sound than MP3 at the same bitrate, but the one with real compatibility gaps. Stick to the
.m4aextension, since Serato on Windows will not read.aacfiles at all. - Ogg Vorbis - free and open source, quality comparable to AAC. Serato and Traktor play it, rekordbox does not, so it is not a safe format to depend on in this scene.
Compressed, lossless
Nothing is thrown away, the data is simply packed more efficiently. Larger than lossy, smaller than uncompressed.
- FLAC - open, no loss of quality, and the best format for storing a library. Note that rekordbox will not export it to a USB for club players.
- ALAC - Apple’s equivalent, with similar file sizes to FLAC. Same rekordbox export restriction, and Serato supports it on Mac and Windows 10 only.
Uncompressed
The full recording with no compression at all. Highest quality, largest files.
- WAV - the standard uncompressed format. Handling of tags and artwork is inconsistent, which matters if your workflow depends on metadata.
- AIFF - Apple’s equivalent with the same audio quality, and more reliable support for embedded artwork and metadata.
For most Zouk DJs a 320 kbps MP3 or AAC is genuinely enough, and lossless is worth taking when it comes without extra cost or hassle. The bigger risk is not the format, it is the source. A file re-encoded from a poor original does not improve by being saved at 320 kbps or converted to FLAC, because the detail is already gone and the filename tells you nothing about where it has been. That is one more reason to get music from official sources, see Buying Music and Music Licensing for DJs.
Check before you trust a format
Supported-format lists change between software versions and player generations, so treat anything here as a starting point rather than a guarantee, and confirm against the current documentation for whatever you actually play on: rekordbox, Serato DJ Pro, Traktor.
MP3 is the only format with no caveats on any of those lists. If a night depends on one file playing, that is the copy to bring.
See Also
Lossy Audio, Lossless Audio, Bitrate, and Performance Sound Quality