What an M4A file is
M4A is an MP4 container holding audio, usually AAC (lossy) and sometimes Apple Lossless (ALAC). It is what the iPhone Voice Memos app records, what iTunes and Apple Music use for DRM-free purchases, and what many Android recorders and messaging apps produce.
AAC is generally more efficient than MP3 at the same bitrate, but MP3 is accepted by more car stereos, older players, websites and editing tools — the main reason to convert.
Bitrate: match or exceed the source
Converting AAC to MP3 is a lossy-to-lossy step, so a little quality is lost every time. Choose an MP3 bitrate at or above the M4A's own bitrate, which the result card shows: voice memos convert well at 128 kbps (or Mono 64–96 kbps), 256 kbps AAC music at 256 or 320 kbps.
Going far above the source adds size without restoring detail. For speech the difference between 96 and 320 kbps is inaudible; for music, 256 kbps is a safe default.
DRM-protected and Apple Lossless files
Songs bought from the iTunes Store before 2009 may be DRM-protected .m4p files; browsers cannot decode them and the converter reports it. Apple Music streaming downloads are also protected. Music you ripped or purchased DRM-free converts normally.
Apple Lossless (ALAC) M4A files decode only in Safari on Mac, iPhone and iPad. In Chrome, Edge or Firefox the converter shows a message; open the page in Safari for those files.
Tags and album art
iTunes-style tags inside the M4A — ©nam title, ©ART artist, ©alb album, aART album artist, track and disc numbers, ©day year, genre and the covr artwork — are read and written to the MP3 as ID3v2.3, so iPhones, Android phones, Windows and car stereos all display them.
Voice memos usually carry only a title (the recording's name or location) and a date; those are copied too.
Converting iPhone voice memos
In the Voice Memos app, tap a recording, then Share → Save to Files, and open this page in Safari to choose the file; or AirDrop or email the memo to a computer. Several memos can be converted at once and downloaded as a ZIP.
If a memo is mono, the converter keeps it mono, and mono at 64–96 kbps is plenty for speech. Everything happens on your device, so private recordings are never uploaded.