Help:Category
The subcategorization feature makes it possible to organize categories into tree-like structures to aid navigation.
Keeping this in mind while reading about categorization, plus learning a category page layout is a worthwhile investment in research techniques.
The MediaWiki software maintains tables of categories, to which any editable page can be added.
Other category pages which appear in this list are treated separately, as subcategories.
A category page can only display a limited number of members (currently 200).
The declaration must be processed, i.e. it will not work if it appears between
For initial lower-case letters, as in Category:macOS, see the technical restrictions page.
If a user has enabled the HotCat gadget, the categories box will also provide links to quickly add, remove, or modify category declarations on the page, without having to edit the whole page.
Raw information about the members of a category, their sort keys and timestamps (time when last added to the category) can be obtained from the API, using a query of the form: Listings of up to 500 members are possible.
English Wikipedia groups accented characters together with their unaccented version, so pages starting with À, Á, Ä, will be listed under heading A.
This means that digit sequences in page names are treated according to their numerical value, not as strings.
If an item ought to be positioned within a list on the basis of an alternative name (sort key) for that item, then this can be specified in the category tag that places the item in the list: For example, to add an article called Albert Einstein to Category:1879 births and have the article sorted by "Einstein, Albert", you would type: Unlike a piped link (which uses the same syntax), the sort key itself is not displayed to readers.
It is possible to set a default sort key which is different from {{PAGENAME}} by using the magic word {{DEFAULTSORT:}}: This is often used in biography articles, to make sure the subject is sorted by their last name: For example, on the Albert Einstein page, {{DEFAULTSORT:Einstein, Albert}} adds the sort key "Einstein, Albert" to all his categories, such as Category:1879 births.
As described at mw:Help:Magic words, {{PAGESINCATEGORY:Example}} or {{PAGESINCAT:Example}} returns the number of pages in "Category:Example".
Categories can be moved in the same way as an ordinary page; but a certain amount of cleanup may be necessary.
On Wikipedia, the magic word is not normally used explicitly, but is applied through the {{hidden category}} template.
The feature is mostly used to prevent project maintenance categories from showing up to ordinary readers on article pages.
Special:TrackingCategories lists all tracking categories populated the MediaWiki software.
Other ways to find relevant articles include searching Wikipedia for the category's topic and searching the Web for the topic in quotes " (with synonyms also in quotes and appended after an OR) and appending the word wiki or Wikipedia or site:Wikipedia.org to them.
When a category link is contained in a template, however, this does not happen immediately: instead, whenever a template is edited, all the pages that transclude it are put into the job queue to be recached during periods of low server load.
This means that, in busy periods, it may take hours or even days before individual pages are recached and they start to appear in the category list.
Performing a null edit to a page will allow it to jump the queue and be immediately recached.
To add the template itself to the category page as well, omit the "includeonly" tags.
Parser functions can be used to make the transcluded categories, or the sort key used in them, dependent on other variables, notably PAGENAME.
On Wikipedia it is not recommended that templates be used to populate ordinary content categories of articles.
Notice that "Related Changes" does not show edits to pages that have been removed from the category.
If a workaround would be required, the links in question could be placed in a template and transcluded onto the category page.
As usual – unlike with watchlists – recent changes to corresponding talk pages are not shown under "Related Changes".
