To extract the audio from an M4A, open it in the converter. This guide explains what the converter does with it and why.
AAC or ALAC?
M4A is an audio container in the MPEG-4 family, not a codec name. AAC is the common payload and is lossy: some information was discarded when the recording was encoded. An M4A can also contain ALAC, the Apple Lossless Audio Codec. That difference changes the quality history of the conversion. AAC to MP3 is a second lossy encode. ALAC to MP3 would start from lossless audio and still end lossy, but in current Chrome and Edge it does not start at all: neither browser can decode ALAC, as the test below shows.
Decide whether you need MP3 at all
If the original opens in the software or device you plan to use, keep it. Converting AAC to MP3 cannot improve it, and raising the MP3 bitrate cannot restore what AAC removed. MP3 is useful when the destination explicitly requires .mp3 or rejects M4A. PrivateMP3 writes MP3 at 192 kbps; there is no bitrate picker.
What each output does with an M4A
| Source and choice | Actual processing |
|---|---|
| AAC → MP3 | Decode AAC and encode a new 192 kbps MP3. |
| ALAC → MP3 or WAV | Needs an ALAC decoder in the browser. Chrome 154 and Edge 154 have none, so there is no waveform and Convert stays off. |
| Unedited AAC → M4A | Copy the AAC packets without re-encoding. The converter shows a copy note. |
| Edited AAC → M4A | Decode and encode new AAC. ALAC is neither copied nor, in those browsers, decodable. |
| Decodable audio → WAV | Decode to a larger 16-bit PCM working file. |
A cut or volume change rules out packet copy because it changes the timeline or sample values. Simply choosing M4A is therefore not a promise of lossless output.
Audacity: convert, or install FFmpeg?
Audacity documents different behavior by operating system. Its macOS build can import unprotected M4A (AAC) and MP4 files as shipped. On Windows and GNU/Linux, M4A (AAC) generally needs the optional FFmpeg library. Installing FFmpeg avoids making an MP3 just to get the file into Audacity. Conversion is the practical alternative when you cannot change that setup or the next device genuinely needs MP3. Protected store files are separate; changing the extension or format does not remove access controls.
Measured: one AAC M4A and one ALAC M4A
Tested on 6 October 2026 in Chrome 154.0.8037.98 and Edge 154.0.4258.53 on Windows 11 (Intel Core i5-13600KF, 32 GB), with files generated by FFmpeg from a 220 Hz tone and quiet pink noise. Times are from Chrome; Edge differed by at most 0.7 s on any row. Each saved file was read back with ffprobe. The method is described in the screen recording test results.
| File, 3:00, 44.1 kHz stereo | File check said | MP3 | M4A | WAV |
|---|---|---|---|---|
| AAC, 4,964,185 bytes | AAC, 219 kbps | 1.5 s, 4,321,018 bytes | 0.09 s, 4,965,348 bytes, unchanged copy | 1.2 s, 31,752,044 bytes |
| ALAC, 24,316,106 bytes | ALAC, 1080 kbps, no decoder in this browser | Convert disabled in both browsers | ||
The AAC file was requested from FFmpeg at 256 kbps; the panel measured 219 kbps from its packets, and the unchanged copy kept exactly that rate. The MP3 came out smaller than the source because 192 kbps is below 219 kbps. That is a lower data rate after a second lossy encode, not a cleaner file.
The ALAC file opened and listed its track, but WebCodecs reported no support for ALAC in either browser, so nothing could be decoded. On a Mac, Apple's Music app can make a converted copy: in Music, choose Settings, Files, Import Settings, pick the format in Import Using, then select the song and choose File > Convert > Create [format] Version. Apple notes that the original and the converted version both stay in the library. (Apple: convert music file formats in Music on Mac) A WAV or AAC version made that way opens in the converter normally.
When there is no waveform
Check that the original still plays in the application that created it. The browser may understand the M4A container but lack a decoder for the codec inside. MP3 and WAV then cannot run. A complete, unedited AAC track may still use the decoder-free M4A copy path; ALAC cannot. A damaged file or misleading extension needs to be re-exported from its original application. Keep the source until you have listened through the result.