M4A to MP3 Converter

Convert M4A files, including iPhone voice memos, to MP3 in your browser. Pick the bitrate you want and the file stays on your own machine the whole time.

The converter is ffmpeg compiled to WebAssembly. It downloads once (30 MB) when you pick your first file, then stays in your browser cache.

A higher bitrate keeps more detail and costs more bytes. 192 kbps is transparent for most music on ordinary gear, 128 is plenty for speech, and 320 is the practical ceiling for MP3.

Your file is processed by your own browser and never uploaded. The engine itself is a one-time 30 MB download the first time you use it, and after that it comes out of your browser cache.

How to use M4A to MP3

  1. 1Drop your .m4a files onto the box above, or click it to pick them. Several at a time is fine.
  2. 2The converter loads once, about 30 MB, then works through the files one after another.
  3. 3Play each result to check it, then download. Take a batch as a single .zip.

Where M4A files come from

Almost everyone who needs to convert M4A to MP3 got the file from one of three places. Voice Memos on an iPhone, which saves recordings as M4A, and the iPhone voice memo to MP3 route is by far the busiest one. iTunes and the Music app, which have used M4A for unprotected purchases and imports for years. Or a phone or camera app that writes audio-only MP4 without telling you.

Nothing is wrong with the format. It is simply less universally accepted than MP3, and the gap shows up in the annoying places: car head units, gym equipment, transcription services with a fixed upload list, DAWs on older versions, and any piece of hardware from before roughly 2010.

This conversion goes downhill, slightly

It is worth being clear about the direction. AAC in an M4A is a lossy encode, and MP3 is a different lossy encode. Going from one to the other means decoding what survived the first pass and letting a second encoder make its own decisions about what to discard. AAC is the better codec of the two at any given bitrate, so you are trading a small amount of fidelity for compatibility.

The practical advice follows from that. For music, use 256 or 320 kbps and the result will be indistinguishable in normal listening. For speech, 128 kbps is already generous and 64 kbps is defensible, because a voice has far less information in it than a full mix.

What the tool preserves

The sample rate is left alone. A 44.1 kHz source produces a 44.1 kHz MP3, and a mono recording stays mono rather than being padded into stereo. Both of those are easy to get wrong, and both matter for transcription tools that assume the file tells the truth about itself.

Everything runs on your machine. The engine is ffmpeg compiled to WebAssembly, downloaded once and then served from your browser cache.

Frequently asked questions

Will the MP3 sound worse than the M4A?
A little, in principle. M4A holds AAC, which is already lossy and is genuinely more efficient than MP3 at the same bitrate, so re-encoding is a small step down rather than a step up. Convert at 192 kbps or higher and the loss is very hard to hear. The reason to do it anyway is that MP3 plays on hardware that has never heard of AAC.
My iPhone voice memo is an M4A. Will this work?
Yes, and it is the most common thing people bring here. Voice memos are usually mono AAC at a modest bitrate, so 128 kbps is plenty and 64 kbps is often fine for speech. There is no need to spend 320 kbps on a recording of someone talking.
Is M4A the same thing as AAC?
Not quite. M4A is a container, essentially an MP4 with no video, and AAC is the codec normally inside it. A file with an .aac extension is a raw stream with no container. Both work here.
What happens to the album artwork?
It is not carried over. Artwork sits inside the file as an image stream, and this tool keeps only the audio. Text tags such as title, artist and album do come across.
Are Apple Music downloads convertible?
Only if they are unprotected. Older purchases and Apple Music downloads can carry DRM, in which case no converter can read them and the tool will report that it cannot decode the file. Your own recordings and unprotected files are fine.

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