M4B Audio — A .m4b file is a M4B Audio. It is an audio format used to store music, voice and sound effects, either lossy or lossless.
Quick facts
What is .m4b
A .m4b file is a M4B Audio. It is an audio format used to store music, voice and sound effects, either lossy or lossless.
In the mime-db registry it maps to audio/mp4, and it is marked as non-compressible. When serving .m4b over HTTP, set the Content-Type header as shown in Developer info below.
Related entities: it maps to audio/mp4 — and is delivered over HTTP via the Content-Type header.
How to open .m4b files
Developer info
When served over HTTP, responses should set the following header:
Content-Type: audio/mp4
Common software that reads/writes .m4b:
Relation chain
Related extensions
Related MIME types
Common uses
How to edit .m4b files
How to create .m4b files
Frequently asked questions
Common options include VLC, Windows Media Player, Audacity. You can also open many of these files with built-in viewers or a browser.
Create a new file in any text editor or the app that owns the format and save it with the .m4b extension.
audio/mp4 is the media type identifier used for .m4b files during network transfer (for example in the HTTP Content-Type header).
Sources & standards
Updated 2026-08-18
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