What are MIME types?

In GNOME, MIME (Multipurpose Internet Mail Extension) types are used to identify the format of a file. The GNOME Desktop uses MIME types to:

  • Determine which application should open a specific file format by default.

  • Register other applications that can also open a specific file format.

  • Provide a string describing the type of a file, for example, in a file properties dialog of the Files application.

  • Provide an icon representing a specific file format, for example, in a file properties dialog of the Files application.

MIME type names follow a given format: 

media-type/subtype-identifier

image/jpeg is an example of a MIME type where image is the media type, and jpeg is the subtype identifier.

GNOME follows the freedesktop.org Shared MIME Info specification to determine:

  • The machine-wide and user-specific location to store all MIME type specification files.

  • How to register a MIME type so that the desktop environment knows which applications can be used to open a specific file format.

  • How the user can change which applications should open what file formats.

What is the MIME database?

The MIME database is a collection of all MIME type specification files that GNOME uses to store information about known MIME types.

The most important part of the MIME database from the system administrator’s point of view is the /usr/share/mime/packages/ directory where the MIME type related files specifying information on known MIME types are stored. One example of such a file is /usr/share/mime/packages/freedesktop.org.xml, specifying information about the standard MIME types available on the system by default. That file is provided by the shared-mime-info package.

Get more information

For detailed information describing the MIME type system, see the freedesktop.org Shared MIME Info specification located at the freedesktop.org website: