Categories are pages that group together pages which share similar purposes, subjects or other qualities. They are a feature of the MediaWiki software this wiki uses. 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 take you 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, a grouping of related pages, and contains an index for the pages of its category. For example, this page belongs to "Category:Help". If you open the category 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.
The category pages themselves contain 2 parts:
- at their beginning, an optional part may contain text that can be edited, like any other page,
- at their end, an ever present, automatically generated, alphabetical list of all pages in that category, in the form of links. In fact, in the Unicode sort order.
New categories can be created before assigning any page to it, in the same way as any other page.
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 pages, 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 the page and the 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.
It may take some time for a page to appear or disappear from a category. Try adding
?action=purge at the end of the URL to nudge the server to do it faster. The wait time may be even longer if assigned through a template.
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 on this wiki are not case sensitive. 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.
Spaces and other characters are perfectly valid. See Wikipedia:WP:SORTKEY for more information and uses.
Removing a category from a page
To remove a category from a page, simply delete the category text from the page. This will automatically remove the page from the Category: namespace and any association with parent categories.
Creating a category page
Categories 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; just add "
Category:" before the page title.
To avoid extra work, try searching within the wiki before creating a new category. The list of all categories can be found in "Special pages" in the "tools" box of the sidebar.
Managing the 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. It is common for a page to share branches from multiple trees.
An example of this hierarchy would be the relationship between Category:Valve and Category:Half-Life. To link the two categories, it is recognized that Half-Life is a game created by Valve. Rather than linking Category:Half-Life directly to Category:Valve, a more appropriate way would be to create an additional category called Category:Valve Games between the two. The hierarchy would then look like Category:Valve → Category:Valve Games → Category:Half-Life. Organizing categories this way cleans up each parent category and offers opportunities for more child categories (or branches) to form.
The categories that a page is in are normally listed at the bottom of the page. However, a category can be hidden from this list by adding the magic word "
__HIDDENCAT__" to the category page.
Users can choose to see hidden categories in a separate hidden-categories list, by checking the Show hidden categories box in Special:Preferences.
Hidden categories are automatically added to Category:Hidden categories.
On this wiki, hidden categories are usually reserved for maintenance categories, such as Category:TODO. Content categories should not be hidden, as they are for reader navigation.
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 other normal or category pages. However, this is not recommended, as pages categorized in redirected categories do not get categorized in the target category.
Categorizing for wiki maintenance
Another function of categorizing pages and files is for wiki maintenance. Whether the category is manually added by a contributor or automatically added by a maintenance template, categories serve to group content requiring attention in a way that is easily manageable.
- Category:Hidden categories - Hidden categories.
- Special:Categories - Lists all categories.
- Special:CategoryTree - Insert a category and this will return categories included under it, categories this one is included under, and the pages in this category. Basically, it's visiting a category page but without actually visiting it.
- Special:MostCategories - Displays pages that have the highest number of categories.
- Special:MostLinkedCategories - Categories most frequently linked to by other categories (basically the biggest categories).
- Special:RandomInCategory - Takes you to a random page in a category.
- Special:TrackingCategories - Auto-generated categories.
- Special:UncategorizedCategories - Lists categories that are not categorized under any others.
- Special:UncategorizedFiles - Lists files that are not listed under any categories.
- Special:UncategorizedTemplates - Lists templates that are not listed under any categories.
- Special:UnusedCategories - Lists categories with no pages in them.
- Special:WantedCategories - Categories that are linked to a lot, but don't officially "exist". This list is not crucial. A category does not need a description to function.