Leave with an MP3 for the places your M4A will not play, from an older car stereo to a basic player or someone else's computer.
Converting M4A to MP3 gives you a file that plays on equipment and software that never learned Apple's format, such as older car stereos, basic MP3 players and some editing tools. Since most M4A files hold AAC, which is already lossy, the audio is compressed a second time, so quality can only hold steady or dip slightly, never rise.
Transfers use HTTPS, and files converted on the free tier are deleted within 24 hours, so the result is not a long-term archive. Quality depends on the source file, so open the MP3 file once before you share it.
M4A (MPEG-4 Audio)
An audio-only MP4 container popularised by Apple. It usually holds AAC, a lossy codec that is more efficient than MP3, and occasionally ALAC, which is lossless. iPhone Voice Memos, iTunes and GarageBand exports all commonly use it.
MP3 (MPEG-1 Audio Layer III)
The oldest widely used lossy audio format, dating from the early 1990s. Its compression is less efficient than AAC, but virtually every car stereo, portable player, operating system and audio program made since can open it.
A 15-second spoken-word clip saved as M4A, converted on indox.org
Once a Voice Memo is saved to Files, or a ripped album sits in a folder, add the .m4a files by dropping them on the box or choosing them from your device. Files kept in Dropbox or Google Drive, or behind a URL, can be imported from there.
Plain AAC and lossless ALAC inside an M4A can both be re-encoded as MP3. Old iTunes Store purchases ending in .m4p and Apple Music downloads are encrypted, so they cannot be converted. A progress bar shows each job, and you can cancel one.
Download the MP3 for a USB stick or a simple player, share it with a link when someone cannot open M4A, or convert it again to another format. AAC is already lossy, so this is a second-generation copy: keep the M4A too.
Choose the .m4a from your device or drop it on the box; Dropbox, Google Drive and URL import work too. For an iPhone Voice Memo, share it from the Voice Memos app to Files first.
Confirm that the converter shows MP3 as the output format, then start the conversion. Copy-protected .m4p files will fail, so leave them out.
Download the MP3 and open it in the player you converted it for. Title, artist and album usually carry over, but cover art does not and audiobook chapters usually do not, so check one file before converting a whole library.
You add an M4A from an iPhone, iTunes or GarageBand and get back an MP3 for equipment and software that do not read Apple's format. You install nothing, and converting one file takes no account. Uploads travel over HTTPS, and free-tier files are deleted within 24 hours. The MP3 cannot sound better than the M4A it came from, because the audio is compressed a second time, and copy-protected files cannot be converted at all.
The upload box shows the live size limit before you add a file. Signing in raises it, and paid plans raise it further.
M4A in, MP3 out. Pick another output on the converter if you need a different format.
Files are encrypted in transit over HTTPS and processed on indox infrastructure.
Free-tier files are deleted automatically within 24 hours after the job finishes.
| What you see | Why | What to do |
|---|---|---|
| The MP3 has no cover art | Only the audio is written, and the picture stream is dropped | Add the artwork again in a tag editor |
| The MP3 sounds a little worse than the M4A | The sound is compressed a second time, with a different codec | Keep the M4A, and go back to a lossless source if you have one |
| The MP3 is a different size than expected | No bitrate is set, so the encoder picks its own | Check the result before you copy it to the device you made it for |
| Compared on | M4A | MP3 |
|---|---|---|
| What it is | Audio in the MPEG-4 container, with the audio/mp4 type and the .m4a extension | A stream of MPEG-1 Audio Layer III frames, not stored in a conventional container |
| Metadata | Held in the MPEG-4 container's own structures | ID3 tags, a separately specified structure |
| Codec | AAC is a common audio codec in the MPEG-4 container | Layer III only |
| Type and extension | audio/mp4, .m4a | audio/mpeg, .mp3 |
Facts checked on October 16, 2026
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Slightly, in most cases. A typical M4A contains AAC, which has already thrown away some audio, and the MP3 encoder then discards a little more using different rules. From a good source the change is hard to hear on everyday equipment. From a small, low-bitrate voice recording, the added harshness and swishing can be obvious.
For sound per megabyte, yes. AAC, the codec inside most M4A files, was designed as the successor to MP3 and delivers similar quality at a noticeably lower bitrate. MP3 wins only on reach: it works on nearly every device ever sold. If your M4A already plays where you need it, converting gains you nothing.
Usually because the stereo was built to read MP3 only, or MP3 and WMA. Many car head units and budget players, older ones especially, ignore AAC entirely, and some skip the .m4a extension even when they can decode AAC. A second cause is copy protection: encrypted .m4p files play only in authorised Apple software.
Share the memo out of the Voice Memos app first, then convert the resulting .m4a file. Use the share button to save it to Files, email it to yourself or AirDrop it to a computer. Voice Memos records AAC by default, with a lossless option on recent iOS versions, and either kind can be re-encoded as MP3.
Only if they are not copy-protected. Songs bought from the iTunes Store without copy protection are plain AAC in .m4a files and convert normally. Older purchases with the .m4p extension and anything downloaded through an Apple Music subscription are encrypted with FairPlay, and no ordinary converter can read the audio inside them.
Mostly, yes. Common fields such as title, artist, album, year and track number have direct ID3 equivalents and are normally copied across. Cover art is not: only the audio stream is kept. Less common data, including chapter lists, lyrics, sort names and gapless playback information, has no dependable equivalent and may vanish. Check a file or two before relying on a converted library.
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