Help:Extension:CategoryTree

As taken directly from the extension page on MediaWiki:

The CategoryTree extension provides a dynamic view of the wiki's category structure as a tree. It uses AJAX to load parts of the tree on demand. CategoryTree was originally written by Daniel Kinzler as an external tool, but was later integrated into the MediaWiki software with the help of Tim Starling.

Usage
CategoryTree can be used in three ways:
 * directly on the category pages,
 * as a "custom tag" (or "parser function") to show a category structure in-line on a wiki page,
 * and as a special page.

The CategoryTree extension adds [+] "expand" widgets to the subcategories listed on category pages. If Javascript is disabled, those widgets take you to the category page (in earlier versions, it did nothing in that case).

If you want arrows ► ► ▼ instead of [+] [x] [-], see this discussion of how it was done for Wikipedia


 * change MediaWiki:Categorytree-expand-bullet to ►
 * change MediaWiki:Categorytree-collapse-bullet to ▼
 * change MediaWiki:Categorytree-empty-bullet to ►

The &lt;categorytree&gt; tag
Example:

The custom tag is called &lt;categorytree&gt;. For example, if you put &lt;categorytree&gt;Foo&lt;/categorytree&gt; on a wiki page, it will show the contents of category Foo as a dynamic tree on that page (see example to the right). The tag accepts the following attributes, using a HTML-like syntax :


 * mode: determines which pages are shown in the tree. This may be overridden by the use of the namespaces option. Possible values:
 * categories: show subcategories only (configuration constant CT_MODE_CATEGORIES)
 * pages: show subcategories and pages, except images (configuration constant CT_MODE_PAGES)
 * all: show all pages, subcategories, images, etc (configuration constant CT_MODE_ALL)
 * parents: list parent categories instead of subcategories (configuration constant CT_MODE_PARENTS). This puts CategoryTree into "inverse" operation (supported since 36892, July 2008).


 * depth: determines how many levels of the tree are shown initially. Default is 1. 0 means only the root node. The maximum value depends on the mode specified, and on the $wgCategoryTreeMaxDepth option. (introduced between r20410 and 20840, Mar 30 2007; fully functional even with $wgCategoryTreeDynamicTag since 36864, July 2008)
 * onlyroot : set this to "on" to only show the "root" node of the tree initially. Equivalent to depth="0". (introduced in 20385, March 13 2007) Deprecated as of 36864, July 2008: use depth="0" instead.
 * hideroot: set this to "on" to hide the "root" node of the tree, i.e. hideroot=on. For example, it will not display the category name Foo.
 * hideprefix: determines when the namespace prefix should be hidden from entries in the tree (since 36864, July 2008). Possible values are:
 * always: always hide the prefix. Should be used only if all pages come from the same namespace (configuration constant CT_MODE_CT_HIDEPREFIX_ALWAYS</tt>).
 * never: never hide the namespace prefix, not even for categories (configuration constant CT_MODE_CT_HIDEPREFIX_NEVER</tt>).
 * auto: hide the namespace of categories, if only categories are shown, as with mode="categories"</tt> (configuration constant CT_MODE_CT_HIDEPREFIX_AUTO</tt>); This is equivalent to the old default behavior (before Jun 2008).
 * categories: always hide the namespace of categories, but show all other prefixes (configuration constant CT_MODE_CT_HIDEPREFIX_CATEGORIES</tt>). This is the new default behavior (since 36864, July 2008).


 * showcount: set this to "on" to show the number of entries in subcategories, i.e. showcount="on"</tt> (since 36864, July 2008). This is disabled per default for category trees inlined on pages, but enabled per default in category listings and on Special:CategoryTree.
 * namespaces: a list of namespaces from which pages should be shown in the tree (since 36864, July 2008). The entries in the list must be namespace names, separated by spaces. The main namespaces can be represented by "-" or "0". This overrides the mode</tt> option.
 * class, style, id, etc: The &lt;categorytree&gt; tag supports all standard HTML attributes for block elements (since 36864, July 2008. Before that, only style</tt> was supported).

The parser function
Since 25825 (2007-9-13), you can also use parser function syntax to place a category tree on a page. This works just like the &lt;categorytree&gt; tag, using a different syntax, e.g.  </tt>; options can be specified using the syntax for named template parameters, e.g.   </tt>.

Using the parser function syntax has the advantage that it allows you to use magic words, templates and template parameters when specifying the category to show. Some examples:
 * Using a magic variable to show "this pages" category tree (may be useful on category description pages):  </tt>.
 * Using a template to specify the category:  </tt> - the name of the root category would be defined by the contents of Template:Root_category.
 * Using a template parameter to specify the category, when using CategoryTree inside a template:  </tt> in Template:Baz can be called using

The Special:CategoryTree page
The special page is called Special:CategoryTree; there you can enter the name of a category and then browse its content.