A Category is a special type of page which provides automatic indexing and is very useful as a tables of contents for a broad topic within the wiki.
You can categorize pages and files by adding one or more Category tags to the content text. These tags create links at the bottom of the page that lead to the list of all pages in that category, which makes it easy to browse related articles.
Each of the pages in the Category namespace represents a so-called category, which is a grouping of related pages, containing an index for all the pages within its category. For example, this page belongs to "Category:Help". If you open the "Category:Help" page, you will see a link to this page there.
When a page belongs to one or more categories, these categories appear at the bottom of the page (when using the default Vector skin).
The category pages themselves contain 2 parts:
- At the top of the article, an optional part may contain text that can be edited like any other page.
- At the end of the category article there is an ever present, automatically generated, alphabetical list of all pages in that category, in the form of links.
To assign a page to a category, simply add the link "[[Category:Category name]]" to the page's wikitext. The usual place to add it is at the bottom of the page.
To create a link to a category page on a given page as a normal wiki link, prefix the link name with a colon. For example: [[:Category:Not in this category]]. This will create a link to the category page but will prevent the page from being added to that category.
New categories can be created before assigning any page to it, in the same way as any other regular page.
Individual wikis may have their own top-level categories, such as Category:Contents in Wikipedia.
For a complete list of all categories which have at least one page, see Special:Categories.
For a complete list of all created/edited categories, including the ones that don't have any page, see Special:Allpages/Category: (note the colon at the end).
Adding a Page to a Category
To add a page or uploaded file to a category, simply edit the page and add the following text (where Name is the name of the category you want to add it to).
Any number of Category tags may be added to a given page and that page will be listed in all of them. Category tags are usually added at the very bottom of the page for the convenience of other editors.
On a categorized page, categories are displayed in the Categories: box strictly in the order they appear in the wikitext.
By default, a page is sorted within a category under the first letter of its name — without the namespace. Also, MediaWiki groups accented characters separately from their unaccented version, so pages starting by À, Á, Ä, will be listed under separate headings, instead of under heading A.
A sort key specifies under which letter heading, and where in the category list, the page will appear. You can add a sort key by placing it inside the tag after a pipe character. For example, the tag below will add the page under heading "S".
Sort keys are case-sensitive, and spaces and other characters are also valid. The order of the sections within a category follows the Unicode sort order. The sort key does not change the page title displayed in the category.
Creating a category page
Categories can exist even if their page has not been created, but these categories are isolated from others and serve little purpose for organization or navigation.
A category is created by creating a page in the Category: namespace. A category page can be created the same way as other wiki pages (see Help:Creating Pages); just add "
Category:" before the page title.
To avoid extra work, try searching within your wiki before creating a new category. The list of all categories can be found in "Special pages" in the "tools" box of the sidebar.
Unlike other wiki pages, it is not possible to rename (move) a category. It is necessary to create a new category and change the Category tag on every page. The new category will not have the older category's page history, which is undesirable if there are many revisions.
Managing Category Hierarchy
Categories may belong to other categories in a hierarchy. Since category pages are much like any other page, a Category tag may be added to the bottom of a category page.
It is a good idea to organize all categories into a hierarchy with a single top level category. The category structure can take the form of a tree with separate branches, but more often will have a graph structure. Generally, there should be a contiguous chain of parent-child links between each category and the top level category.
Linking to a category
To create a link to a category, use a leading colon before the category name (without this colon, the current page would be added to the category):
To change the link text, write the text inside the link tag after a pipe:
[[:Category:Help|Help category]]→ Help category
Redirect pages that redirect to categories must also use the colon, otherwise they will be added to the category instead of redirecting.
Redirecting a Category
Like normal wiki pages, category pages can be redirected to category pages or even other normal pages. However, this is not recommended, as pages categorized in redirected categories do not get categorized in the target category.