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M4A to MP3 converter

Convert M4A (AAC) audio to universally compatible MP3 format.

Free & unlimited
All processing happens in your browser — files never leave your device. The audio engine loads once from a CDN.

M4A is a container, normally holding AAC audio, that Apple devices produce by default — voice memos, iTunes purchases, GarageBand bounces. It plays fine on Apple hardware and on modern Windows and Android, and badly or not at all on older car stereos, gym equipment, DAB players and cheap MP3 players. This converter re-encodes the AAC inside your M4A to MP3 using libmp3lame, running in your own browser. Four quality presets cover 320, 256, 192 and 128 kbps, with an optional VBR mode and an optional -16 LUFS loudness pass. iTunes tags and embedded artwork are carried over by default. Drop a whole folder in and the batch download comes back as a ZIP.

Key facts about M4A to MP3 converter

Key facts about M4A to MP3 converter
What M4A actually isAn MPEG-4 container. It normally holds AAC, but an Apple Lossless (ALAC) file also uses the .m4a extension — both decode here
This conversion is lossy to lossyAAC is decoded and re-encoded as MP3, so artefacts from the original encode are baked in and new ones added
Bitrate presets320 kbps maximum, 256 high, 192 balanced, 128 compact
VBR optionSwitches libmp3lame to quality level 2, which averages around 190 kbps and varies with the material
MetadataiTunes tags, track info and embedded artwork are copied to the MP3 by default; turning preservation off strips them entirely
Optional normalizeApplies a loudnorm pass at -16 LUFS with a -1.5 dBTP ceiling during conversion
Typical size changeA 256 kbps M4A converted to 320 kbps MP3 gets about 25 percent larger without sounding better; 192 kbps MP3 is usually a similar size to the source
Compatibility gainedMP3 plays on essentially every device ever built with a digital audio output, including car head units from the early 2000s
BatchMultiple files per run, downloaded individually or as one ZIP
Size cap200 MB per file

What happens to your file

The conversion runs on ffmpeg compiled to WebAssembly inside a Web Worker in this tab. Your M4A files are written into that worker's in-memory filesystem, encoded to MP3, and read back as blobs — nothing is uploaded, nothing is queued, and no account exists. The ZIP for batch downloads is assembled in the browser too. One network request happens: the first time you use any audio tool here, the browser downloads the ffmpeg core (about 32 MB) from the jsDelivr CDN and caches it. That asset is identical for every visitor and carries no part of your files.

About this tool

  1. 1

    Add your M4A files

    Drop one file or a whole selection. Each must be under 200 MB, which covers several hours of typical AAC audio.

  2. 2

    Pick a bitrate

    192 kbps is the sensible default for a file that came from a 256 kbps AAC. Going to 320 makes the file bigger without recovering anything the AAC encode already discarded.

  3. 3

    Decide on VBR

    Variable bitrate gives a better quality-to-size ratio on varied material. Leave it off if the target device is old enough that VBR MP3 playback might stutter or report the wrong duration.

  4. 4

    Keep or strip metadata

    Preservation is on by default and carries iTunes tags and artwork across. Turn it off when you want a clean file with no identifying information in it.

  5. 5

    Convert

    Files are processed one at a time with per-file progress. The summary line shows the exact settings being applied.

  6. 6

    Download

    Take files individually, or use the ZIP download when you have converted a whole album or a folder of voice memos.

Specs & compatibility
InputM4A (.m4a, audio/mp4, audio/x-m4a), up to 200 MB per file
OutputMP3, libmp3lame, constant or variable bitrate
Bitrates128, 192, 256 or 320 kbps
Metadata carriedTitle, artist, album, track and embedded cover art
Batch outputIndividual downloads or a single ZIP built client-side
EngineSingle-threaded ffmpeg.wasm 0.12.10, ~32 MB core cached after first use
BrowsersChrome, Edge, Firefox and Safari 15+
SpeedA four-minute track typically converts in a few seconds once the engine is loaded
  • Do not convert a 128 kbps M4A to 320 kbps MP3. The extra bitrate stores the AAC's artefacts more faithfully and nothing else.
  • 192 kbps MP3 is roughly transparent against a 256 kbps AAC source for most listening, and keeps the file size close to the original.
  • If the M4A is an Apple Lossless file rather than AAC, you are converting from a lossless source — in that case 320 kbps or VBR is genuinely worth it.
  • Leave metadata preservation on if the files are going into a music library; stripping it means retagging everything by hand afterwards.
  • Voice memos convert well at 128 kbps mono. If the source is stereo speech, use the general audio converter to downmix and halve the size again.
  • The ZIP download is built in your browser from the converted blobs, so a very large batch is limited by memory rather than by any server.
  • MP3 is the format to pick for old hardware. If the target is a modern phone or computer, the M4A already plays fine and converting gains nothing.
  • Four bitrate presets from 128 to 320 kbps
  • Optional MP3 variable bitrate
  • iTunes tag and artwork preservation
  • Optional -16 LUFS loudness pass
  • Batch conversion with per-file progress
  • ZIP download for whole folders
  • Handles both AAC and Apple Lossless inside .m4a
  • Getting iPhone voice memos onto a device that only reads MP3
  • Converting an iTunes library so it plays in an older car stereo
  • Preparing AAC recordings for a podcast host that requires MP3
  • Making GarageBand bounces playable on Windows machines with no codec support
  • Turning a folder of M4A lecture recordings into MP3s for a portable player
  • Converting audiobook chapters bought as M4A into MP3 for a device that will not open them
Yes, a little, and there is no way around it. The AAC inside an M4A is already lossy, and converting to MP3 means decoding it and encoding again with a different lossy codec. Everything the AAC encoder discarded stays gone, and the MP3 encoder discards a bit more. In practice, at 192 kbps or above, most people cannot hear the difference on a 256 kbps AAC source. Convert only when you actually need MP3 for compatibility, and keep the M4A as your master.
192 kbps for most M4A files, which typically hold 128 to 256 kbps AAC. That keeps the size close to the original and is transparent enough for normal listening. Choose 320 only when the source is Apple Lossless rather than AAC, because then you really are encoding from a lossless master and the extra bitrate buys something. Choose 128 for speech — voice memos, lectures, audiobooks — where it is entirely sufficient and halves the file compared to 256.
Yes, by default. Metadata preservation is on, and the tags and embedded artwork inside the M4A are written into the MP3's ID3 tags during conversion. That matters for iTunes purchases and ripped albums, where retagging a hundred files by hand is not a reasonable alternative. You can switch preservation off if you want a file with no identifying information attached — that maps the metadata away entirely, leaving nothing but the audio.
Yes. Select or drop as many M4A files as you like; they are converted one after another with per-file progress, and you can download each result individually or take the whole set as a single ZIP. The ZIP is built inside your browser from the converted blobs, so there is no server involved and no upload — which also means a very large batch is bounded by your device's memory rather than by any queue or quota.
It does. Both AAC and Apple Lossless (ALAC) use the .m4a extension, and the decoder handles either. The difference is what it means for quality: an ALAC file is a lossless master, so encoding it to MP3 is a single lossy generation rather than a second one, and using 320 kbps or VBR is genuinely worthwhile. If you are converting ALAC and want to keep losslessness, use the general audio converter and choose FLAC instead of MP3.
No. The encoding is done by ffmpeg compiled to WebAssembly, running in a Web Worker on your own device. Your M4A files go into that worker's in-memory filesystem and come back out as MP3 blobs; nothing crosses the network. The single request the tool makes is fetching the ffmpeg core itself — about 32 MB of fixed public code from the jsDelivr CDN, cached by your browser and shared across every audio tool here. Your files play no part in it.

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