FLAC Files Not Playing on Your CDJ? Here is Why

You exported your Rekordbox library to a USB, plugged it into the CDJ at the venue, and your FLAC files show up in the browser but refuse to play. The CDJ loads the waveform preview for a split second, then stops. No audio. No error message. Just silence.

This is one of the most frustrating problems in DJing, and the reason is simple: your CDJ does not support FLAC playback.

Which CDJs Support FLAC?

ALAC (Apple Lossless) and M4A files have the same problem - unsupported on all older CDJs. The only universally supported formats are MP3, WAV, and AIFF.

Why the CDJ Shows the File but Won't Play It

Rekordbox exports file metadata (title, artist, BPM, cue points) to the USB regardless of format. The CDJ reads this metadata and shows the track in the browser. But when it tries to decode the audio, it does not have a FLAC decoder, so playback fails silently.

This is especially confusing because the CDJ shows the waveform and all the track info - it just will not produce any sound.

Quick Fix: Convert One Track

If you just need one track converted for tonight's gig, you can do it manually:

1. Open the FLAC file in any audio converter (fre:ac, XLD, Audacity, even iTunes)
2. Export as MP3 320kbps or WAV
3. Add the new file to Rekordbox
4. Add it to your USB export playlist
5. Re-export the USB

This works for one or two tracks. For an entire library of FLAC files across multiple playlists, it is not practical.

The Real Fix: Convert Your Entire Library

If your library is primarily FLAC, ALAC, or M4A, you need a way to convert everything at once while keeping your Rekordbox playlist structure intact. This is exactly what Mirrorbox does.

Mirrorbox connects to your Rekordbox library, identifies every track that won't play on a CDJ, converts them to MP3 (or WAV or AIFF), and rebuilds your playlists with the converted files. Tracks that are already in a compatible format pass through without being touched.

The result is a mirrored version of your playlists with CDJ-compatible files - same structure, same order, same metadata. Export to USB and everything plays.

Related Guides

• How to Convert FLAC Files Without Losing Your Playlists - the full conversion guide
• How to Fix Missing Files in Rekordbox - another common CDJ preparation problem
• Rekordbox Library Management: A Complete Guide - all tools and solutions compared