What is MIME type "audio/x-m4b"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

audio/x-m4b is a MIME type for audio files that use the Advanced Audio Coding (AAC) format.

It is commonly used for audiobooks because it supports features like chapter markers and bookmarks. This means you can pause and resume playback easily and navigate between chapters.

The format is container-based, similar to other types that use AAC. It is related to formats such as MP4 and M4A, though it often provides additional features for spoken-word content.

Other files using AAC include formats like 3GP, AAC, and M4P. However, M4B is specifically tailored for audiobook use.

Primarily used for audiobooks with chapter and bookmarking support.
Based on the AAC standard for efficient audio compression.
Utilizes a container format similar to MP4 to embed rich metadata.
Compatible with many modern media players and audiobook apps.

For more technical details, see MPEG-4 Part 14.

Associated file extensions

.mp4, .m4a, .3gp, .aac, .m4b, .m4p

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: audio/x-m4b

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="audio/x-m4b">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');
    
    http.createServer((req, res) => {
      res.setHeader('Content-Type', 'audio/x-m4b');
      res.end('Content here');
    }).listen(3000);

Associated file extensions

.mp4, .m4a, .3gp, .aac, .m4b, .m4p

FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.