What is MIME type "multipart/appledouble"?

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

multipart/appledouble is a MIME type that encapsulates a file split into separate parts. One part holds the file’s primary data while the other contains Mac-specific metadata such as resource forks and extended attributes.
This separation ensures that extra Mac information is not lost when the file is shared on systems that do not support such details.

Functionality involves packaging a file into dual components. This is important when a file coming from a Mac system needs to be transferred to non-Mac environments.
It prevents issues like data corruption or loss during email transmissions and cross-platform transfers.

Preservation: Keeps metadata like icons and file comments intact.
Compatibility: Enables Mac files to be used on Windows or Linux without losing essential file details.
File Transport: Often applied to email attachments and archives where the full Mac file structure must be maintained.

This MIME type is associated with file types such as ADF, RSRC, and AD.

Associated file extensions

.adf, .rsrc, .ad

Usage Examples

HTTP Header

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


    Content-Type: multipart/appledouble

HTML

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


    <a href="file.dat" type="multipart/appledouble">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', 'multipart/appledouble');
      res.end('Content here');
    }).listen(3000);

Associated file extensions

.adf, .rsrc, .ad

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.