Convert M4A to MP3
Convert M4A voice memos and Apple audio to MP3 in your browser. Batch queue, bitrate control, no upload and no file size limit.
- Runs in your browser
- Files are never uploaded
- Free, no account
First use downloads the 10 MB video engine from this site. After that it is cached and works offline. It is WebAssembly served by onthisdevice.com — never a third-party CDN — and your file is still processed entirely on your own device.
What an M4A file actually is
M4A is a container, not a codec — it is an MPEG-4 file that happens to hold only audio. Inside, it is almost always AAC, the codec Apple standardised on for iTunes, Voice Memos and QuickTime. Occasionally it holds Apple Lossless (ALAC) instead, which is a genuinely lossless format that some people rip CDs to. Both decode here without you needing to know which you have.
The reason M4A causes trouble is not quality — AAC beats MP3 at the same bitrate — it is reach. Car head units, gym equipment, DJ software, older Android builds, transcription services and a good deal of embedded hardware read MP3 and nothing else.
Picking a bitrate
| Source | Suggested MP3 bitrate | Why |
|---|---|---|
| Voice Memo, dictation, interview | 96–128 kbps, mono | Speech has little high-frequency content; forcing mono halves the size again |
| Podcast episode | 128 kbps | The industry norm; higher is inaudible over headphones on a commute |
| Music from iTunes (256 kbps AAC) | 256 kbps | MP3 is less efficient, so match the number rather than the perceived quality |
| GarageBand bounce you will keep | 320 kbps | Maximum MP3 quality; export a WAV from GarageBand if you plan to edit further |
About the quality you lose
AAC is already lossy. Decoding it back to samples and encoding those as MP3 is a second generation of loss, and the two codecs discard slightly different things, so the artefacts compound rather than overlap. In practice the effect is inaudible for speech at any sensible bitrate and very hard to hear on music at 192 kbps or above. Two rules keep you safe: encode at or above the source bitrate, and always keep the original M4A, because it is the only copy that has been through the mill once instead of twice.
Converting a whole folder of Voice Memos
Select every file at once — the queue converts them one after another with its own progress row for each, and offers a single ZIP when it is finished as well as individual downloads. There is no per-day quota and no ten-files-per-hour meter, because there is no account and no server keeping count. On a modern laptop a five-minute memo converts in a couple of seconds.
The privacy point, stated plainly
Voice memos are the single most sensitive category of everyday audio: therapy notes, medical appointments, legal calls, interviews under embargo, song ideas you have not published. Every upload-based converter asks you to trust a retention policy. This page cannot receive your file because it has no server behind it — the conversion happens in FFmpeg compiled to WebAssembly and running in this browser tab, and the site’s Content-Security-Policy permits no third-party origin at all. Open the Network tab and convert something: after the one-time engine download, nothing moves.
What will not work
- .m4p files. Those are DRM-protected iTunes Store purchases from before 2009, encrypted with FairPlay. No local tool can decode them and this one will tell you so rather than producing a broken file.
- Audiobooks with chapters. A .m4b converts, but MP3 has no equivalent chapter structure, so the chapter marks are lost and you get one long track.
- Files that are actually video. A .mp4 with a picture track works fine — only the audio is taken — but if you wanted the video too, use the video converter.
Related conversions
If your files are raw AAC streams rather than M4A, AAC to MP3 is the same engine with the right dropzone. Going the other way, or needing an uncompressed master for an editor, use MP3 to WAV. To stitch several memos into one file first, try the audio joiner.
Questions
Will converting M4A to MP3 lose quality?
A little, unavoidably. M4A holds AAC, which is already lossy, so decoding it and re-encoding as MP3 is a second generation of loss. At 192 kbps or above the difference is inaudible for speech and very hard to hear on music. Keep the original M4A if you may need to convert again later.
Where do M4A files come from?
Apple Voice Memos, GarageBand exports, iTunes purchases, and most phone recorders. M4A is a container (MPEG-4 audio) rather than a codec, so it usually holds AAC and occasionally ALAC. Both decode here.
Can it convert a whole folder at once?
Yes. Drop or select up to 50 files, and they convert one after another with a progress row each. When more than one finishes you get a single ZIP as well as individual downloads. There is no daily quota, because there is no account and no server.
My M4A is a DRM-protected iTunes purchase.
Older iTunes Store purchases use the .m4p extension and Apple FairPlay DRM. No local tool can decode those and this one will report that it cannot read the file. Music bought since 2009 is DRM-free and converts normally.