M4A to MP3 Converter

Convert M4A audio to MP3 without uploading it. Useful when a car stereo, an older player or a piece of software will not take M4A - which is the only good reason to do this conversion.

Runs entirely in your browser. Nothing is uploaded.

FromM4AAAC in an MP4 container
ToMP3Plays on anything

Constant bitrate.

Mono halves the size of speech.

Matching the source avoids a resample.

Drop M4A files here, or

Converted on this device. Nothing is uploaded.

MP3 encoding by LAME, via lamejs, used under the LGPL and loaded as a separate file you can replace.

How to use the M4A to MP3 Converter

  1. Drop in your M4A files

    One or many. They are decoded by your browser and never transmitted.

  2. Set the bitrate to 192 kbps or higher

    This is a second lossy encode, so give it room. 128 kbps on top of an already-compressed source is where it starts to be audible.

  3. Wait for the encode

    The progress bar is real - the encoder runs in a background worker, so the page stays usable while it works.

  4. Play it, then download it

    Check the result on the page before saving, particularly if you dropped the bitrate.

This conversion makes the audio worse. Do it anyway, for the right reason

An M4A holds AAC, which is a lossy codec: detail was discarded when the file was made. Converting it to MP3 decodes what is left and throws away more, and at the same bitrate MP3 is the weaker of the two codecs. So the result is second-generation lossy audio in the less efficient format - strictly worse than the original at any setting you choose.

The reason to do it regardless is compatibility, and it is a good reason. Car head units, older iPods and DAPs, gym and PA equipment, cheap Bluetooth speakers, plenty of DAWs and almost every hardware sampler will take an MP3 and will not take an M4A. A file that plays is worth more than a file that is technically better and silent.

What you should not do is convert an M4A to MP3 to "improve" it, to "make it standard", or before archiving it. Keep the M4A. Make the MP3 for the device that needs one.

Choosing a bitrate for a second-generation encode

The usual advice about MP3 bitrates assumes you are encoding from a master. You are not - you are encoding from a file that has already been through a codec, and the artefacts it left behind are now part of the signal the MP3 encoder is trying to reproduce. Encoding artefacts is expensive, and it is a poor use of the bits.

Use 192 kbps as the floor and 256 kbps if the source was good and the size does not matter. 320 kbps is not wrong but rarely earns its extra third of a megabyte per minute here. Go below 192 only for speech - a voice memo at 128 kbps mono is perfectly intelligible and a quarter of the size.

When an M4A will not open at all

Not every `.m4a` holds AAC. Apple Lossless uses the same extension and the same container, and no browser decodes it - if a file is refused here and it came out of iTunes, that is the likely reason. A `.m4p` is a DRM-protected purchase from the old iTunes Store and will not decode anywhere, by design.

There is also a browser question. AAC is a licensed codec, so Chromium builds compiled without the proprietary codecs - which is most Linux distribution packages - cannot decode M4A at all. Chrome, Edge and Safari can, and on Windows and macOS so can Firefox. The page checks for this when it loads and says so before you waste a drop on it.

Frequently asked questions

Will converting M4A to MP3 lose quality?
Yes, and there is no setting that avoids it. The M4A is already lossy, so this is a second lossy encode on top of a first. Convert because something cannot play M4A, not to improve the file, and use 192 kbps or higher.
Is my audio uploaded anywhere?
No. The file is decoded by your browser and encoded by a worker running on your own device. Nothing is transmitted - which matters more than usual for audio, because a voice memo is a recording of a person.
Why was my .m4a refused?
Most likely it is Apple Lossless or a DRM-protected .m4p, neither of which any browser can decode, despite the shared extension. The other possibility is a browser built without the AAC decoder, which the page warns about when it loads.
Can I convert a batch at once?
Yes, and they are converted one after another rather than all at once. That is deliberate: decoded audio is large in memory, and running four files in parallel is how a browser tab runs out of it.
Is the MP3 the same length as the M4A?
Within a few milliseconds. AAC carries encoder delay and padding that the decoder strips, and MP3 adds a small amount of its own, so the two files are not sample-identical in length. It only matters if you are aligning to a grid.