Audio conversion
Convert M4A to M4B
M4A and M4B are nearly the same audio format, both built on AAC audio inside an MP4 container. Converting M4A to M4B mainly relabels the file so audiobook and podcast apps recognize it, remember where you stopped listening, and keep it separate from your music. Doing this on your own computer means the recording never has to leave your machine.
All 2,748 conversions verified on macOS, Windows, and Linux against the shipping release, this one included. Every conversion runs entirely on your own computer.
- Extension
- .m4a
- Type
- Audio
- Typically
- iTunes / voice memos
- Compression
- Lossy
- Extension
- .m4b
- Type
- Audio
- Typically
- Audiobooks, podcasts
- Compression
- Lossy
Convert M4A to M4B on your own computer. Nothing uploads.
One-time purchase, no subscription. 14 days to change your mind.
How to convert M4A to M4B
- Open Morphjet and drag in the M4A file, or a whole folder of voice memos or recordings at once.
- Choose M4B as the output format.
- Convert. The M4B is written next to your original, and nothing leaves your machine.
M4A vs M4B: what actually changes
| M4A | M4B | |
|---|---|---|
| File size | Compact, AAC-compressed audio | About the same, same audio codec |
| Quality | Lossy AAC, fine for speech and music | Same lossy AAC, no meaningful loss on conversion |
| Opens in | Any music or media player | Also opens anywhere, but audiobook and podcast apps recognize it specifically |
| Remembers your place | No, plays from the start each time | Yes, most audiobook apps bookmark your position |
| Shows up in your library as | A song, mixed in with your music | A book, kept in an audiobook or podcast shelf instead |
| Chapter markers | Only if the file already has chapter metadata | Same, converting doesn't add chapters that weren't there |
When to convert, and when not to
Convert M4A to M4B when you have a long recording, an audiobook rip, or a multi-part voice memo that you want your phone or audiobook app to treat as a book, so it remembers where you stopped and keeps it out of your music playlists.
Keep the M4A if it's a short clip, a song, or anything you want sitting in your regular music library, since M4B is meant for long-form spoken audio and most apps will file it under books instead of tracks.
Why not just use an online converter?
Files people convert to M4B are often personal, voice memos, dictated notes, interviews, or recordings of someone's own voice. Sending that through an online converter means it sits on a stranger's server while it processes. Converting on your own computer keeps the recording, and whatever is said in it, on your machine the whole time.
Questions
Does converting M4A to M4B lose audio quality?
Barely, if at all. Both formats use the same AAC audio, so the conversion is mostly a container and metadata change rather than a full re-encode. You shouldn't hear a difference.
Will converting to M4B add chapter markers?
No. M4B supports chapters, but conversion only carries over what's already in the file. If your M4A didn't have chapter markers, the M4B won't either.
Why does M4B remember where I stopped listening and M4A doesn't?
It's a difference in how apps treat the file, not the audio itself. Audiobook and podcast apps look for the M4B label and use it to save your playback position, where music apps just play M4A tracks from the start.
Can I convert a whole folder of voice memos to M4B at once?
Yes. You can drag in a folder of M4A files and convert them all in one pass instead of doing them one at a time.
Can I convert M4A to M4B without uploading the file anywhere?
Yes. A desktop app like Morphjet converts the file locally, so it never travels over the internet. You can do it with your wifi off.
Morphjet runs this conversion and 2,747 others, all on your machine. Available now.
One-time purchase, no subscription. 14 days to change your mind.