An iPhone voice memo won't open on Android, in Audacity, or on older players because it's saved as .M4A — an AAC-based format some apps don't support. Converting the M4A to MP3 makes it play and edit almost anywhere, and you can do it in your browser without uploading the recording.
Why won't my M4A voice memo open?
iPhones save Voice Memos as .M4A (AAC audio in an MP4 container). MP3 is universal; M4A isn't — some Android apps, older media players, car stereos, and audio editors like Audacity (without the right add-on) can't open it. The recording itself is fine; the format just isn't recognised.
The fix: convert M4A to MP3
Convert M4A to MP3 and it opens on Android, in Audacity, in transcription tools, and on virtually any player. It runs in your browser, so the recording isn't uploaded — which matters for private notes, interviews, and meetings.
Is there a quality loss?
Both M4A and MP3 are lossy, so converting re-encodes once — but at a reasonable bitrate it's inaudible for speech, and voice memos are speech. Quality is rarely a concern here; if you want the details, see why does my converted audio sound worse.
Editing a voice memo?
If you're trimming an interview or cleaning up a lecture, convert to MP3 first so Audacity and other editors open it reliably, then edit from there. Keep the original M4A as a backup until you're done.
Convert privately in your browser
M4A to MP3 runs on your device — nothing uploaded. Other Apple/AAC audio that won't open? AAC to MP3. For the general approach, see why won't my video or audio file play.
Why the file plays on your phone but not your PC
An .m4a is AAC audio inside an MP4 container — the same container as a video file, without the video track. Apple has used it as the default for Voice Memos for years. The audio itself is a mainstream format, so the problem is almost never the codec: it is that an older player looks at the extension, does not recognise it, and refuses before it ever inspects the contents.
That is why renaming .m4a to .mp4 sometimes appears to work in a media player, and why it is still the wrong fix. The file has not changed, only the label, and anything that inspects the contents properly will find audio where it expected video. Converting to MP3 changes the actual encoding and produces a file that every device, transcription service and upload form accepts.
Keep the original if the recording matters
MP3 is lossy, and the M4A was already lossy, so converting re-encodes audio that has been compressed once before. For a lecture, an interview or a legal recording, keep the .m4a as the master and treat the MP3 as the copy you send. One conversion is inaudible; repeatedly converting the same recording between lossy formats is not.