AnyFormat

00 M4A → MP3

M4A to MP3

Voice memos and iTunes audio, playable everywhere.

Drop files or a folder here

or choose from your device · paste with ⌘V / Ctrl+V

.m4a .m4b

03Options 5

Right for speech, wrong for music. At a fixed quality the file size does not change — but mono tolerates a much lower quality than stereo, so combine the two to actually shrink the file.

Leave at 0 for the whole file.

0 means run to the end.

  • No upload The conversion runs in this tab. Your file never travels — not to us, and not to the advertising.
  • No sign-up, no email, no daily cap There is no account system to sign up to.
  • No size limit we invented Only your device's memory — about ~2 GB on a desktop browser, ~400 MB on a phone.
  • Turn your Wi-Fi off and convert anyway The conversion needs nothing but this page. Ads will not load without a connection; your file will still convert. That is the whole claim, and it takes five seconds to check.

Converts M4A to MP3. M4A is AAC audio in an MP4 container — what iTunes, Apple Music and iPhone voice memos produce. It sounds better than MP3 at the same bitrate and is refused by a long tail of hardware, which is why this conversion exists at all.

You are trading quality for compatibility

AAC is a more efficient codec than MP3: at the same bitrate it sounds better, and this conversion goes the wrong way down that gradient and adds a lossy generation.

If the target device accepts M4A, do not convert. Most things made after about 2010 do. Convert when something specifically will not: an older car stereo, gym equipment, a hardware player, a corporate system that only accepts .mp3 uploads.

Use High quality to keep the second generation inaudible.

Voice memos and the .m4b case

iPhone voice memos are M4A and convert straight through. They are mono speech, so Low quality with mono selected produces a very small file that sounds identical.

.m4b — the audiobook variant — is the same format with a different extension and a chapter track. It converts, and the chapter markers do not survive: MP3 has no equivalent.

How MP3 encoding works without a server

Browsers decode MP3 but do not encode it — there is no MP3 encoder in WebCodecs. The encoding here is LAME, the reference open-source MP3 encoder, compiled to WebAssembly and loaded only when you actually convert to MP3.

It is the same encoder desktop software has used for twenty years, producing standard files that play everywhere. Because it is fetched on demand, pages that convert to WAV or M4A never download it.

Purchased files cannot be converted

A file bought from the iTunes Store before 2009, or anything downloaded from Apple Music, is DRM-protected. It will not convert here or anywhere else — that is the entire purpose of the protection, and no converter can or should get around it.

Files you recorded yourself, ripped from your own CDs, or bought DRM-free convert normally. If a file fails and you are not sure which it is, try playing it on a device that is not signed in to the account that bought it.

Other names for this

Also searched as “m4a to mp3 converter”, “voice memo to mp3”, “aac to mp3”.

Questions

Will it sound worse?
Slightly, in principle — it is a second lossy encode into a less efficient codec. At High quality it is inaudible on normal material.
My M4A came from Apple Music and fails.
Purchased or streamed Apple Music files are DRM-protected and cannot be converted. Files you recorded or ripped yourself are fine.
Can I convert an audiobook .m4b?
Yes. The audio converts; chapter markers do not, because MP3 has no chapter concept.
Is my file uploaded?
No. The demuxing, decoding and encoding all happen in this tab using the browser’s own media stack plus a WebAssembly encoder. A recording can be an interview, a lecture, a private call — none of it is transmitted. Turn your Wi-Fi off after the page loads and it still works.
How large a file can I convert?
There is no imposed limit, only your device’s memory — around 2 GB in a desktop browser and 400 MB on a phone, since the file is held in memory while it converts. A two-hour video converts in well under a minute on a laptop.
Can I convert several files at once?
Yes. Drop as many as you like, or a whole folder. Each keeps its original name with the new extension, and you can download them individually or as a ZIP.