Convert MPEG-4 Audiobook (.m4b) to MPEG-4 Audio (.m4a) online for free. Fast, secure audio conversion with no watermarks or registration.
Upload your .m4b file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .m4a file when it's ready.
M4B and M4A are both MPEG-4 Audio containers — the difference is that M4B signals audiobook content to players (enabling chapter navigation and bookmark resume), while M4A is treated as standard music. Converting M4B to M4A is essentially a container relabel: the AAC audio data, metadata, and even artwork are identical. The only functional change is that players no longer treat the file as an audiobook, losing chapter markers and the auto-bookmark feature.
Music apps and general-purpose players categorize M4A as music and M4B as audiobooks. Converting to M4A puts audiobook content in the music library. Podcast apps accept M4A but often reject M4B. Audio editors and production tools may not recognize M4B but handle M4A without issues. Some file-sharing platforms accept M4A but filter out M4B.
FFmpeg performs a stream copy from M4B to M4A. The AAC audio frames are transferred bit-for-bit. The chapter track (if present) is discarded during remuxing since M4A files conventionally do not include chapter tracks. iTunes metadata atoms (title, artist, album, artwork) are preserved. The operation is instant regardless of file length.
Zero quality change. The audio data is bit-identical. This is a container relabel, not a transcoding operation.
| Device | M4B | M4A |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Native |
| iPhone/iPad | Partial | Native |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No |
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Resolution: N/A
Bitrate: 256 kbps
AAC format required
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
M4B to M4A is the simplest conversion — a container relabel that changes how players categorize the content. Audio quality is completely preserved.
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| No |
| Funktion | M4B | M4A |
|---|---|---|
| Fulde navn | MPEG-4 Audiobook | MPEG-4 Audio |
| Filendelse | .m4b | .m4a |
| Bedst til | Chapter support | Better than MP3 |