<page xmlns="http://projectmallard.org/1.0/"
type="topic"
id="mime-types">
<info>
<link type="guide" xref="software#management" />
<link type="seealso" xref="mime-types-application" />
<link type="seealso" xref="mime-types-application-user" />
<link type="seealso" xref="mime-types-custom-user" />
<revision pkgversion="3.12" date="2014-06-17" status="review"/>
<credit type="author">
<name>Petr Kovar</name>
<email>pknbe@volny.cz</email>
</credit>
<include href="legal.xml" xmlns="http://www.w3.org/2001/XInclude"/>
<desc>MIME types are used to identify the format of a file.</desc>
</info>
<title>What are MIME types?</title>
<p>
In GNOME, MIME (<em>Multipurpose Internet Mail Extension</em>)
types are used to identify the format of a file. The GNOME Desktop
uses MIME types to:
</p>
<list>
<item>
<p>
Determine which application should open a specific file format by
default.
</p>
</item>
<item>
<p>
Register other applications that can also open a specific file format.
</p>
</item>
<item>
<p>
Provide a string describing the type of a file, for example,
in a file properties dialog of the <app>Files</app>
application.
</p>
</item>
<item>
<p>
Provide an icon representing a specific file format, for
example, in a file properties dialog of the <app>Files</app>
application.
</p>
</item>
</list>
<p>
MIME type names follow a given format:
</p>
<screen>
<var>media-type</var>/<var>subtype-identifier</var>
</screen>
<p>
<sys>image/jpeg</sys> is an example of a MIME type where
<sys>image</sys> is the media type, and <sys>jpeg</sys>
is the subtype identifier.
</p>
<p>
GNOME follows the <em>freedesktop.org Shared MIME Info</em>
specification to determine:
</p>
<list>
<item>
<p>
The machine-wide and user-specific location to store all MIME type
specification files.
</p>
</item>
<item>
<p>
How to register a MIME type so that the desktop environment knows which
applications can be used to open a specific file format.
</p>
</item>
<item>
<p>
How the user can change which applications should open what file formats.
</p>
</item>
</list>
<section id="mime-database">
<title>What is the MIME database?</title>
<p>
The MIME database is a collection of all MIME type specification files
that GNOME uses to store information about known MIME types.
</p>
<p>
The most important part of the MIME database from the system administrator’s
point of view is the <file>/usr/share/mime/packages/</file>
directory where the MIME type related files specifying information on
known MIME types are stored. One example of such a file is
<file>/usr/share/mime/packages/freedesktop.org.xml</file>, specifying
information about the standard MIME types available on the system by
default. That file is provided by the <sys>shared-mime-info</sys>
package.
</p>
</section>
<section id="mime-types-more-information">
<title>Get more information</title>
<p>
For detailed information describing the MIME type system, see the
<em>freedesktop.org Shared MIME Info specification</em> located at the
freedesktop.org website:
</p>
<list>
<item>
<p>
<link href="http://www.freedesktop.org/wiki/Specifications/shared-mime-info-spec/">
http://www.freedesktop.org/wiki/Specifications/shared-mime-info-spec/</link>
</p>
</item>
</list>
</section>
</page>