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.M4B·File Extension

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.

Audioaudio/mp4

Quick facts

Extension.m4b

File typeM4B Audio

MIME typeaudio/mp4

CategoryAudio

Charset—

CompressibleNo

What is .m4b

What is a .m4b file?

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

Use VLC or Windows Media Player to open and edit .m4b files.
Any text editor (Notepad, VS Code) can inspect the raw content as text.

Developer info

When served over HTTP, responses should set the following header:

Content-Type: audio/mp4

Common software that reads/writes .m4b:

VLCWindows Media PlayerAudacityQuickTime

Relation chain

.m4bextension of

format

M4B Audioserved as

mime type

audio/mp4sent via header

http header

Related extensions

Related MIME types

Common uses

Music and podcasts
Sound effects
Voice recordings

How to edit .m4b files

Open the file with VLC, make your changes and save.
Most editors preserve the original formatting and encoding — avoid changing the charset.

How to create .m4b files

Create a new file and save it with the .m4b extension, or export this format from VLC.

Frequently asked questions

What programs can open .m4b files?

Common options include VLC, Windows Media Player, Audacity. You can also open many of these files with built-in viewers or a browser.

How do I create a .m4b file?

Create a new file in any text editor or the app that owns the format and save it with the .m4b extension.

What is the relationship between .m4b and the audio/mp4 MIME type?

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 2026-09-13

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