# MIME

MIME (or Multipurpose Internet Mail Extensions) is a standard for sending multimedia file types by e-mail. File types are identified by their MIME type, a value that specifies the type and subtype of the data. For example, the MIME type used to identify JPEG files is image/jpeg.

MIME type information is included with most files sent over the Internet. This information is used by Mosaic to determine the type of file. If a MIME type is not provided, Mosaic uses the file extension to determine the file type. After determining the file type, Mosaic either handles the file type internally or sends the file to the appropriate helper application.

If Mosaic cannot handle the file type and an appropriate helper application is not available, the Unhandled File Type dialog is displayed. This dialog allows you to save the file without viewing it; configure a helper application and view the file; or cancel the file transfer.

To determine the MIME type for a given file type:

1. Open the list of registered MIME types.

2. Choose the MIME type that best describes the file type.

3. If none of the registered MIME types describe the file type, you can define your own MIME type/subtype. For the type part of the MIME type, use one of the following types:

   - text
   - multipart
   - message
   - application
   - image
   - audio
   - video

   If none of these types describe the file type, use the application type.

4. Use your own description for the subtype. To distinguish your subtype from registered subtypes, type "x-" before the subtype. For example: application/x-acad

Additional information:

- MIME FAQ
- Technical overview of MIME (RFC 1521)
- MIME type registration procedure

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