Help:Category

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Categories are a software feature of MediaWiki. They provide automatic indexes that can be useful as tables of contents for browsing, and for automated edits.

You can and should 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.

Summary

Each of the pages in the Category namespace category, a grouping of related pages, and contains an index for the pages of its category. For example, this page belongs to "Category:Advanced editing". If you open the "Category:Advanced editing" 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 the beginning/top, an optional part may contain text that can be edited, like any other page,
  • at the end, an ever present, automatically generated, alphabetical list of all pages in that category, in the form of links. (In fact, in ASCII order. See Help:Special page).

To assign a category to a page, 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 link a category page within a page as a normal wiki link (without adding the page to the category), prefix the link name with a colon. For example: [[:Category:Not in this category]]

New categories can be created before assigning any page to them, in the same way as any other regular page. They can also just be added to a page, which creates a "red" link, then that page can be edited and saved. Categories should form a hierarchy, so unless the new category is the top-level category on the wiki, it should also be assigned to a parent category.

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 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).

[[Category:Name]]

Any number of Category tags may be added to the page and the page will be listed in all of them. Category tags, along with interwiki language links which appear below the Tools section on the sidebar, 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.

If $wgUseCategoryBrowser is set to true, under the first list each category is listed again, breadcrumb-style, with all its parent categories, sorted alphabetically. (At least in MediaWiki 1.18.2) if a category is a subcategory of more than one parent, both hierarchies will be listed, but the tagged category will be stripped off all but one of these. This creates the potential for what appear to be duplicate entries if a category with multiple parents and more than one of its parents are tagged on a page. For example suppose Maryanne is a subcategory of both Mary and Anne. If a page tags categories Maryanne and Anne then the Category breadcrumbs will show

Anne 
Anne
Mary -> Maryanne

"Anne" appears to be duplicated, but what is meant is

Anne 
Anne -> Maryanne
Mary -> Maryanne

This is probably a bug, and has been reported in Bug 33614.

Sort key

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 (and not following A, but following Z). MediaWiki is Anglo-centric by default, so for languages with a lot of diacritics (accented characters), a lot of additional work is required to sort entries correctly.

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".

[[Category:Name|Sort]]

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. In particular, a leading space in the sort key will cause that page to file at the beginning of the list of pages in the category.

See Sorting for further information on category sorting.

DEFAULTSORT magic word

Pages can also be assigned a sort order based on the magic word {{DEFAULTSORT:<intended sort>}}. For example, German has some established non-accented versions of their accented characters, like ue for ü and ss for ß. For the page or category "Bücher" to be properly sorted, the following code could be added at the bottom of the wikitext: {{DEFAULTSORT:Buecher}}

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 (see Starting a new page); 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 the category hierarchy

Categories may (and generally should!) 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.

Hidden categories

The categories that a page is in are normally listed at the bottom of the page. In Mediawiki 1.13+, a category can be hidden from this list by adding the magic word "__HIDDENCAT__" to the category page. Hidden categories are not hidden from category pages.

Users can choose to see hidden categories in a separate "Hidden categories" list, by checking "Show hidden categories" in the "Appearance" section of Special:Preferences.

Hidden categories are automatically added to Category:Hidden categories. This category is specified in the system message MediaWiki:Hidden-category-category.

This designation can be useful for administrative tracking of pages. For example, all pages with videos, or all pages which share some other characteristic which may otherwise be difficult to find by searching.

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):

[[:Category:Editing]]Category:Editing

To change the link text, write the text inside the link tag after a pipe:

[[:Category:Editing|Editing category]]Editing 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.

Tracking categories

Certain syntax issues, such as a broken image link, or too many expensive parser functions, can cause a page to be added to a tracking category. See Help:Tracking categories for details.

General guidelines

Categories are an essential organizational tool for wikis. They allow for the logical grouping of pages (and files) for ease of access. All wikis should have a hierarchical category structure. The actual names of the categories vary from wiki to wiki and community to community, but their structure should be essentially the same.

All wikis should:

  • have a top-level category from which all other categories hang. This category can be called Content, or Browse, or Main or it can be the {{SITENAME}} or any other name which makes sense in the context of the wiki. It should logically reflect that it encompasses the entire contents of the wiki
  • have no uncategorized categories except the top-level category
  • have no uncategorized pages
  • have no uncategorized images
    • for wikis with many images, this is especially important. Having no image categories makes finding existing images near impossible. Taking the time to establish useful image categories greatly reduces this problem
    • some suggested image categories include (but are not limited to): wiki skin images, user images, screenshots, concept art, icons
  • have no uncategorized templates. Even a single "Templates" category is useful, though on wikis which use many templates, have some sub-categories which are more specific is definitely useful