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M4A to MP3.
It works, and it is a second generation of loss. Read the caveat. An M4A is what an Apple Music or iTunes purchase arrives as, and a fair amount of older DJ software and hardware would rather have an MP3. If that is the wall you have hit, this gets you past it.
Drop tracks to convert
WAV, AIFF, FLAC, MP3 or M4A. Drop a whole folder’s worth — one set of settings is applied to all of them and they come back as a single archive. Nothing is uploaded; the page makes no network request.
What it costs
Lossy to lossy, and worth a pause.
The part every other converter leaves out, because it is the part that sometimes says don't.
This is lossy to lossy, which means a second round of an encoder throwing audio away — and the second round works on material the first one already thinned out. It is the one conversion in this set worth pausing over. If you can buy or download the track as a lossless file instead, do that; if you cannot, convert at 320 so the second generation costs as little as possible.
MP3 plays on everything — every CDJ, every controller, every laptop, every pool download. That universality is the entire reason to make one. Modern CDJs read M4A/AAC directly, so check the booth before assuming you need this at all.
The four that matter
What each format is for
Ogg and Opus are missing on purpose: no CDJ reads either, so neither belongs in a DJ's library.
| Format | Size, roughly | What it is for |
|---|---|---|
| WAV | 10 MB a minute | Uncompressed and universal. Opens in everything ever written. Poor at holding tags, which is the one reason to prefer AIFF. |
| AIFF | 10 MB a minute | The same audio as WAV in a container that tags properly. What Rekordbox is happiest with and what every CDJ in service reads. |
| FLAC | About two-thirds of WAV | Lossless compression — identical samples, a third less disk, and a checksum so the file can prove it years later. Read by Rekordbox and the CDJ-3000, but not by the CDJ-2000NXS2. |
| MP3 | About 2.4 MB a minute at 320 | Lossy, permanent, and universal. The right last step for a stick and the wrong middle step in any chain. |
The rule underneath all of it: lossless to lossless costs nothing and can be undone, lossless to lossy costs audio you cannot get back, and lossy to lossless costs disk and recovers nothing. Only the middle one is a real decision.
Frequently asked
Common questions
Does M4A to MP3 lose quality?+
Yes, twice. The M4A was already made by discarding audio, and the MP3 encoder now discards more from what is left — worse, the two encoders disagree about what matters, so the second one spends bits preserving artefacts of the first. At 320 the damage is small and most people will not hear it; at 128 it is a genuinely poor file.
Do I actually need to convert it?+
Often not. The CDJ-2000NXS2 and CDJ-3000 both read AAC in an M4A container, and Rekordbox imports it happily — so if your gear is from the last decade the file probably works as it is. Convert when something specifically refuses it, not on principle.
What about protected iTunes files?+
Older iTunes purchases carried DRM and cannot be decoded by anything that is not Apple, this tool included — the browser will simply refuse to open them. Anything bought since Apple dropped protection is a plain AAC file and converts normally. If a file will not load, that is usually the reason.
Do my files get uploaded anywhere?+
No, and that is the main reason to use this rather than a site that asks you to wait for an upload. The M4A is decoded, re-written as MP3 and handed back entirely inside this browser tab — open the network panel and watch it stay empty. There is no server behind the page, which means an unreleased promo is safe to drop on it and nothing is sitting in somebody's bucket afterwards.
Can I convert a whole folder at once?+
Yes. Drop as many files as you like, set the format once, and the whole queue is converted with a report for each file — what it came from, what it went to, and how the size compares. The results come back as a single archive rather than as thirty separate downloads, which is what you want when the next step is dragging a folder into Rekordbox.
Do the tags come across?+
Yes. Artist, title, album, album artist, genre, year, track number, label, remixer, composer, BPM, key, ISRC, comment and the cover art are all read off the M4A and written into the MP3, so a converted folder arrives in Rekordbox named rather than as a wall of filenames. The one thing that does not travel is anything a DJ program keeps in its own private frames — Serato's cue points and beat grid live in an undocumented block that nothing outside Serato reads, and no converter can carry them.
Is there a file size limit?+
Up to 800 MB per file, which is about 75 minutes of 24-bit stereo audio — a full recorded set fits comfortably. Past that it is the browser's own decoder that gives up rather than the tool.
How does this tool make its FLAC and MP3 files?+
The lossless formats are written here, and verified: every test file was decoded again by an independent decoder and compared sample by sample against the original, with zero differences. On real records the FLAC comes out at about 67% of the uncompressed size, which sits between the standard encoder's default setting and its slowest one. MP3 uses the reference encoder that has been the answer to that problem for twenty-five years, because a homemade one would not make bigger files, it would make worse-sounding ones.
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M4A to WAV · M4A to AIFF · FLAC to MP3 · WAV to MP3 · AIFF to MP3 · Every direction
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