Convert MPEG-4 Audiobook (.m4b) to MPEG-4 Part 14 (.mp4) 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 .mp4 file when it's ready.
M4B is technically an MP4 container with a different file extension and audiobook-specific features (chapters, bookmarks). Converting M4B to MP4 is a near-trivial container relabel — the AAC audio data is identical in both formats. The practical effect is that players and systems recognize the file as generic multimedia rather than an audiobook, enabling upload to platforms that accept MP4 but not M4B.
Many platforms accept MP4 but not M4B: social media, web embedding, CMS uploads, video hosting services, and learning management systems. Converting to MP4 makes audiobook content uploadable to these platforms. Some automated media pipelines only process files with the .mp4 extension. The conversion enables broader distribution of audiobook content outside dedicated audiobook platforms.
FFmpeg performs a stream copy from M4B to MP4. The ftyp brand code changes from M4B to isom or mp42. The AAC audio frames transfer bit-for-bit. Chapter tracks are typically stripped (MP4 supports chapters but most players ignore them). The operation is instant.
Zero quality change. The audio data is bit-identical between M4B and MP4 containers. This is a metadata-level operation, not a transcoding step.
| Device | M4B | MP4 |
|---|---|---|
| Windows PC | Partial | Native |
| macOS | Partial | Native |
| iPhone/iPad | Partial | Native |
| Android | Partial | Native |
| Linux | Partial | Native |
| 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 MP4 is a simple relabel operation for platform compatibility. It enables audiobook content to flow through any system that handles the ubiquitous MP4 format.
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| Native |
| Tính năng | M4B | MP4 |
|---|---|---|
| Tên đầy đủ | MPEG-4 Audiobook | MPEG-4 Part 14 |
| Phần mở rộng | .m4b | .mp4 |
| Phù hợp nhất cho | Chapter support | Universal compatibility |