Audio conversion
Convert AAC to M4B
AAC is the everyday compressed audio format behind purchased music downloads, podcasts, and streaming downloads. M4B is the audiobook version of that same kind of file, built so players remember where you stopped and can jump between chapters. To convert AAC to M4B, open the file in a converter and export it as M4B, right on your own computer, with nothing uploaded anywhere.
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
- .aac
- Type
- Audio
- Typically
- Apple / streaming audio
- Compression
- Lossy
- Extension
- .m4b
- Type
- Audio
- Typically
- Audiobooks, podcasts
- Compression
- Lossy
Convert AAC to M4B on your own computer. Nothing uploads.
One-time purchase, no subscription. 14 days to change your mind.
How to convert AAC to M4B
- Open Morphjet and drag in the AAC file, or a whole folder of AAC chapters, tracks, or lectures.
- Choose M4B as the output format.
- Convert. The M4B is written to your computer, and the audio never leaves your machine.
AAC vs M4B: what actually changes
| AAC | M4B | |
|---|---|---|
| Built for | Music, podcasts, general audio | Audiobooks, podcasts, spoken word |
| Remembers your playback position | No, plays from the start each time | Yes, most audiobook apps resume where you left off |
| Chapter markers | Not supported | Supported, so you can jump between chapters |
| File size | Compact | About the same, since it's the same underlying audio |
| Quality | Lossy | Lossy, no meaningful change if the audio itself isn't re-encoded |
| Opens in | Any music or podcast app | Audiobook apps and most players, though a few basic players ignore the chapter and bookmark features |
When to convert, and when not to
Convert AAC to M4B when you have spoken word audio, an audiobook, a lecture series, or a multi-part recording, and you want your player to treat it as one book that remembers your place and lets you jump between chapters.
Keep the file as AAC if it's music or something you want to play track by track in a normal music app, since M4B is meant for long-form listening, not song playback.
Why not just use an online converter?
Long recordings converted to M4B are often personal, a lecture, a memoir, a recorded session, something you're turning into an audiobook for yourself. An online converter means that recording gets uploaded to a server you don't control before you get the file back. Converting on your own computer keeps the audio exactly where it started, on your machine.
Questions
Does converting AAC to M4B lose audio quality?
Not meaningfully. M4B is a container built on the same family as AAC, so the conversion is mostly about repackaging the audio with chapter and bookmark support, not recompressing it from scratch.
Will the M4B still play in a regular music app?
Usually, yes, but you'll lose the point of converting. Regular music apps often play M4B as one long track without chapters or resume support, which is exactly what audiobook and podcast apps are built to handle.
Does converting to M4B add chapters automatically?
The M4B format supports chapter markers, but the conversion itself won't invent chapters that weren't already there. If your AAC files are already split by chapter, they carry over as separate chapters in the M4B.
Can I convert AAC to M4B without uploading the file?
Yes. A desktop app like Morphjet converts the file locally, so a personal recording or lecture never has to leave your computer.
Why use M4B instead of just keeping separate AAC tracks?
M4B bundles everything into one file that remembers where you stopped and lets you skip between chapters, which is much closer to how audiobook and podcast apps expect long recordings to behave.
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.