Convert M4B to MKV — Free Online Converter
Convert MPEG-4 Audiobook (.m4b) to Matroska Video (.mkv) online for free. Fast, secure audio conversion with no watermarks or registration....
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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 .mkv file when it's ready.
About M4B to MKV Conversion
MKV (Matroska Video) is an open container that supports virtually every codec, including AAC audio from M4B. Converting M4B to MKV packages audiobook content in Matroska's versatile container, which natively supports chapter markers — a feature that aligns perfectly with M4B's audiobook chapters. Unlike converting to M4A or MP3, an MKV conversion can preserve the audiobook's chapter structure in Matroska's chapter specification.
Why Convert M4B to MKV?
MKV is one of the few formats besides M4B that supports rich chapter metadata. Media servers like Plex and Jellyfin display MKV chapters in their player UI. If you want to move audiobooks out of Apple's ecosystem while preserving chapter navigation, MKV is an excellent target. MKV also supports multiple audio tracks, external subtitle files, and embedded cover art — useful for enhanced audiobook experiences.
Common Use Cases
- Archiving audiobooks in an open format that preserves chapter markers
- Adding audiobook content to Plex or Jellyfin media servers with chapter navigation
- Combining audiobook audio with subtitle tracks (for accessibility) in a single MKV
- Creating multi-language audiobook editions with selectable audio tracks in MKV
- Packaging audiobook audio with embedded cover art and metadata in an open container
How It Works
FFmpeg copies the AAC audio from M4B into an MKV container (stream copy, zero quality loss). M4B chapters can be mapped to Matroska chapter metadata during the mux operation. Matroska chapters support titles, timestamps, nested chapters, and language tags — actually richer than M4B's chapter format. The operation is near-instant since no transcoding occurs.
Quality & Performance
Zero quality change with stream copy. The AAC audio data is transferred bit-for-bit from the M4B container to the MKV container.
Device Compatibility
| Device | M4B | MKV |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No | No |
Recommended Settings by Platform
Spotify
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Apple Music
Resolution: N/A
Bitrate: 256 kbps
AAC format required
SoundCloud
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Podcast
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
Tips for Best Results
- 1Explicitly map chapters during conversion to preserve the audiobook's navigation structure
- 2Use MKVToolNix for a GUI-based approach to chapter editing and metadata management
- 3Add the audiobook cover as a Matroska attachment for display in compatible players
- 4For Plex libraries, set the metadata (title, author, narrator) correctly for proper library organization
Related Conversions
M4B to MKV is uniquely advantageous because MKV can preserve chapter structure. It is the best open-format target for audiobooks that need to maintain navigability.