This directory contains any number of XML files, each of which describe a collection of MIME types. By default, the freedesktop.org.xml file is installed in the /usr/share/mime/packages directory. This file contains all the default MIME types that are widely used and recognized.

Applications which provide information about new MIME types are to install a single new XML file here. Depending on the prefix where the application is installed, it will create the file in the /mime/package subdirectory of one of the directories in $XDG_DATA_HOME:$XDG_DATA_DIRS. For example, an application installed to /usr/bin should install a new source XML file to the /usr/share/mime/packages directory. For more information about the XML files in the packages directory, please see the section called “The source XML files”.

These directories and files are automatically generated from the collection of source XML files in the <MIME>/packages/ subdirectory by the update-mime-database application. For example, for each mime-type element in the /usr/share/mime/packages/freedesktop.org.xml file, a directory is created at /usr/share/mime/ with the media type of the MIME type. An XML file is created in that directory with the subtype identifier of that MIME type as well. The contents of the created XML file include comments (and translations for them), subclasses designations and aliases.

<?xml version='1.0' encoding='utf-8'?>
<mime-type xmlns="https://www.freedesktop.org/standards/shared-mime-info" type="text/plain">
<!--Created automatically by update-mime-database. DO NOT EDIT!-->
  <comment>plain text document</comment>
  <!-- possibly more translations -->
  <comment xml:lang="es">documento de texto sencillo</comment>
  <comment xml:lang="eu">testu soileko dokumentua</comment>
  <comment xml:lang="fi">perustekstiasiakirja</comment>
  <comment xml:lang="fr">document plein texte</comment>
  <!-- possibly more translations -->
</mime-type>

Contains one line with a MIME type and a glob pattern, separated by a colon. Files which match the glob pattern are resolved to the MIME type specified before the colon. There are special rules about how filenames are matched by the glob pattern; for more details see the XDG shared mime specification.

This file is also generated by the update-mime-database application, using the default source XML file freedesktop.org.xml.

A binary file which contains information on how to resolve MIME types by “sniffing” the content of the file. This is generally a set of one or more rules such as “check for the string %PDF- at byte offset 0 in the file; if found, assign it the MIME type application/pdf”.

This file is also generated by the update-mime-database application.

Contains a mapping of XML namespaces to MIME types. Each line contains three fields, the namespace, the localName and the MIME type. Each field is separated by a space. If the localName is empty, then there are two spaces between the namespace and the MIME type.

This file is also generated by the update-mime-database application.

Contains a list of aliases for each MIME type. An alias is simply a MIME type that is sometimes known as another type. For each line in this file there are two fields: the first field is the alias name, and the second field is the MIME type. The fields are separated by a space.

This file is also generated by the update-mime-database application.

Contains a list of subclassed MIME types and their “parent” MIME type. From the XDG shared mime specification:

The format of this file is similar to the aliases file. Each line contains two fields, where the first field is the subclassed MIME type and the second field is the parent MIME type. Each field is separated by a space.

This file is also generated by the update-mime-database application.