Wikipedia:Categorization: Difference between revisions
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{{Short description|Wikipedia editing guideline}}
<noinclude>{{pp-semi-indef}}{{pp-move-indef}}</noinclude>
{{Hatnote|"WP:CATEGORY" and "WP:CAT" redirect here. You may be looking for [[Wikipedia:Contents/Categories]] (a list of top-level categories), [[Wikipedia:WikiProject Cats|WikiProject Cats]], [[Wikipedia:HotCat]], [[Wikipedia:WikiProject Categories|WikiProject Categories]], or [[Wikipedia:WikiCat]]. For the category system itself, see [[:Category:Contents]].}}
{{Redirect|WP:CG|computer-generated imagery|Wikipedia:WikiProject Computer graphics}}
{{about|proper use of the categorization function|information on the mechanics of the function, category syntax, etc.|Help:Category|quick answers|Wikipedia:FAQ/Categorization}}
{{Subcat guideline|editing guideline|Categorization|WP:CAT|WP:CATEGORY|WP:MOSCAT}}
{{Guideline list}}
The primary purpose of the '''categorization''' system on Wikipedia is to provide navigational [[Wikipedia:Links|links]] within a structured, [[#Category tree organization|tree-like hierarchy]] of '''categories'''. By grouping pages according to their essential, [[Wikipedia:DEFINING|defining]] characteristics, the system allows readers to browse and efficiently locate related topics.
Proposals to delete, merge, or rename categories should follow the process outlined at [[WP:Categories for discussion|Categories for discussion]]. Please use that forum before undertaking extensive re-categorization of existing categories or the mass creation of new ones.
==Categorizing pages==
[[File:Category explanation.ogv|thumb|A screencast showing how to categorise pages and explaining the usage of the [[Wikipedia:Tools|tool]] [[WP:HOTCAT|HotCat]]]]
{{details|Help:Category}}
{{see also|Wikipedia:Categorization dos and don'ts|Wikipedia:Categorizing redirects}}
Every [[Wikipedia:Page name|Wikipedia page]] should belong to at least one category, except for [[Wikipedia:Talk page|talk pages]], [[Wikipedia:Redirect|redirects]], and [[Wikipedia:User page|user pages]], which may optionally be placed in categories where appropriate.
{{anchor|CATSPECIFIC}}{{shortcut|WP:CATSPECIFIC}}Each categorized page should be placed in the {{em|most specific}} categories to which it logically belongs. And [[#SUBCAT|subcategories]] should be categorised under the {{em|most specific}} [[#PARENTCAT|parent categories]] possible.
Pages (and sub-categories) should not normally be placed in both a given category and any of its subcategories or parent categories. For exceptions to this, see [[#Eponymous categories|§ Eponymous categories]] and [[#Non-diffusing subcategories|§ Non-diffusing subcategories]].
* For example, the article "Paris" need only be placed in [[:Category:Cities in France]], ''not'' also in [[:Category:Populated places in France]]. Because the first category (cities) is in the second category (populated places), readers are already given the information that Paris is a populated place in France by it being a city in France.
{{a note}} [[Wikipedia:Stub#How to mark an article as a stub|stub templates]] categorize stub articles for maintenance purposes into [[#Wikipedia administrative categories|administrative categories]], not for user browsing, so they do ''not'' count as categorization for the purposes of Wikipedia's categorization policies. An article which has a "stubs" category on it ''must'' still be filed in the most appropriate content categories, even if one of them is a direct parent of the stubs category in question.
{{OOUI icon|alert}} '''''Important:''''' Since all categories form part of a [[#Category tree organization|tree-like hierarchy]], ''do not add categories to pages as if they are [[Tag (metadata)|tags]]''.
== Creating category pages <span class="anchor" id="CREATECAT"></span> ==
{{shortcut|WP:CREATECAT}}
Sometimes proper categorization requires the creation of a new category.
===Before creating a new category <span class="anchor" id="BEFORECAT"></span> ===
{{shortcut|WP:BEFORECAT}}{{main|Wikipedia:Categories, lists, and navigation templates|Wikipedia:Overcategorization}}
{{see also|Help:Sortable tables}}
Categories are not the only means of enabling users to browse sets of related pages. And categories have [[WP:DOAC|several disadvantages]], including that categories only show ''the page name'' of each page being categorized, therefore:
*While the [[#Category description|category description]] may provide broader information, individual category members cannot be annotated with descriptions or comments, so they give no context or elaboration for any specific entry.
*There is no provision for referencing any specific entry, to [[WP:V|verify]] a page meets a category's criteria of inclusion.
So, consider whether a [[WP:LIST|list]] would be more appropriate for such a grouping of pages. Lists would also be more useful where it is important to see dates, for example, a [[list of Nobel laureates]]. And can provide options for sorting the entries.
Also, consider whether the category might be considered category clutter. Please see [[Wikipedia:Overcategorization]], for more information on this.
=== Choosing a name for the category <span class="anchor" id="CATNAME"></span> ===
{{shortcut|WP:CATNAME}}{{Main|Wikipedia:Category names}}
{{see also|#Naming conventions}}
A good category name is accurate and '''[[Wikipedia:Neutral_point_of_view#Naming|neutral]]''', and, as much as possible, defines the category's inclusion criteria in the name itself.
{{OOUI icon|alert}} ''Important:'' Moving non-conventionally categorized pages to another category name (see {{tl|Category redirect}}) imposes an additional overhead – an edit for ''every'' categorized page and subcategory.
So, when choosing a name for the category, please be sure a similar category does not exist. Before creating a category, try to find it under a similar name. You can search existing category names as described [[Help:Searching|here]] (top of page). Another way to determine if suitable categories already exist for a particular page is to check the categories of pages concerning similar or related topics.
*For example: You might want to add a subcategory for people to [[:Category:Mexicans]]. By starting at [[:Category:People by nationality]], you will discover that Mexicans are placed in [[:Category:Mexican people]].
{{OOUI icon|information}} ''Note:'' [[#Eponymous categories|Eponymous categories]] (categories whose name and topic is the same as an article, such as a category named after a person) should only be created if enough directly related articles exist.
=== Creating the category ===
After you have determined an appropriate category name for the category, next try to find a suitable place for the new category. (For example, categories of people should be in the [[:Category:People|tree of "people" categories]].) Please see [[#Category tree organization]] for more information on this.
Once you have determined where to categorize this new category, you should be ready to create the new category.
To create a category:
# Add a page to the intended category. Do this by editing that page, and add the name of the new category: (e.g.: {{code|[[Category:New category name]]}} )
#* {{Anchor|CATORDER}}{{Shortcut|MOS:CATORDER}}By convention, categories are placed at the end of the wikitext, but before any [[Wikipedia:Stub|stub]] templates, which transclude their own categories.
#* [[#Eponymous categories|Eponymous categories]] should appear first. Beyond that, the order in which categories are placed on a page is not governed by any single rule (for example, it does not need to be alphabetical, although partially alphabetical ordering can sometimes be helpful). Normally the most essential, significant categories appear first. <!-- There is currently no [[WP:CON|consensus]] about the order in which categories should be placed at the bottom of an article. -->
# Save your edit. The as-yet-undefined category name will now appear as a [[Wikipedia:Red link|red link]] in the category list at the bottom of the page.
#* {{Anchor|CATREDLINK}}{{Shortcut|WP:CATREDLINK}} A page should never be left with a non-existent ([[Wikipedia:REDLINK|redlinked]]) category on it. Either the category should be created, or else the link should be removed or changed to a category that does exist.
# Next, click on that red link, which brings you to the new category page to create.
# Finally, at the bottom of the category page, simply add the parent category (e.g.: {{code|[[Category:Parent category name]]}} ), which should usually be a [[hypernym]] of the subcategory. This will add the new category into the appropriate parent category.
{{OOUI icon|alert}} ''Important:'' If something goes wrong, double check to see if you followed the steps properly and check if the wikitext is correct. For example, if the category fails to list in the parent category, the wikitext should be {{xtn|<nowiki>[[Category:Parent category name]]</nowiki>}}, not <nowiki>[[:Category:Parent category name]]</nowiki>.
=== Category description <span class="anchor" id="CATDESC"></span> ===
{{shortcut|WP:CATDESC}}
While it should typically be clear from the name of an existing category which pages it should contain, sometimes, a common-sense guess based on the name of the category isn't enough to figure out whether a page should be listed in the category. So, rather than leave the text of a category page empty (containing only parent category declarations), adding a main article which describes the topic, see {{section link|#Articles with eponymous categories}}, can help with that.
However, only linking to a Wikipedia article explaining the title is often not sufficient as a description for a category. It can be helpful – to both readers and editors – to include a clear description of the category, indicating what pages it should contain, how they should be subcategorized, and so on, and linking to one or more pages as background information.
In such cases, the desired contents of the category should be described on the category page, similar to how the [[WP:LSC|list selection criteria]] are described in a stand-alone list. The category description should make direct statements about the criteria by which pages should be selected for inclusion in (or exclusion from) the category. This description, not the category's name, defines the proper content of the category. Do not leave future editors to guess about what or who should be included from the title of the category. Even if the selection criteria might seem obvious to you, an explicit standard is helpful to others, especially if they are less familiar with the subject.
The description can also contain links to other Wikipedia pages, in particular to other related categories which do not appear directly as subcategories or parent categories, and to relevant categories at [[Wikipedia:Wikimedia sister projects|sister projects]], such as [[Wikipedia:Commons|Commons]]. Another technique that can be used is described at [[Wikipedia:Classification]]. Like [[Wikipedia:Disambiguation|disambiguation]] pages, category pages should not contain either citations to [[Wikipedia:Identifying reliable sources|reliable sources]] or [[Wikipedia:External links|external links]].
Various templates have been developed to make it easier to produce category descriptions; see [[:Category:Category namespace templates|Category namespace templates]]. There are hatnote templates including {{tl|Category main article}} and {{tl|Category see also}}; others are listed at [[Wikipedia:Hatnote#Categories]].
=== Additional considerations ===
Categories may have hundreds of members, displayed over many pages, with, at most, only 200 category entries on a single category page. To make navigating large categories easier, a table of contents can be used on the category page. The following templates are some of the ways of doing this:
* {{Tl|Category TOC}} – adds a complete table of contents (Top, 0–9, A–Z)
* {{Tl|Large category TOC}} – adds a complete table of contents with five subdivisions for each letter (Aa Ae Aj Ao At)
* Consider using <code>{{tl|CatAutoTOC}}</code> which uses the appropriate TOC for the number of pages on a category page.
Likewise, a maximum of 200 subcategories are displayed at a time, so some subcategories may not be immediately visible. To display all subcategories at once, add a category tree to the text of the category page, as described at {{Section link|Help:Category#Displaying category trees and page counts}}.
Category pages can have [[Help:Interlanguage links|interlanguage links]] in the "Languages" list in the left sidebar (in the default skin), linking to corresponding categories in other language Wikipedias. To edit these on [[Wikidata]], click on the "Edit links" link at the end of the languages list.
== Categorizing articles <span class="anchor" id="ARTICLES"></span><span class="anchor" id="Articles"></span> ==
{{For|category types to avoid|Wikipedia:Overcategorization}}
In general, categories of articles must be:
*{{Anchor|V|Verifiable|Verifiability|CATV}}{{Shortcut|WP:CAT#V|WP:CATV}} '''''[[Wikipedia:Verifiability|Verifiable]]''''': It should be clear from verifiable information in the article why it was placed in each of its categories. Use the {{tl|Unreferenced category}} template if you find an article in a category that is not shown by sources to be appropriate or if the article gives no clear indication for inclusion in a category.
*{{Anchor|POV|NPOV|CATPOV|POVCAT}}{{anchor|Neutral|N}}{{Shortcut|WP:CAT#N|WP:CATPOV|WP:POVCAT}} '''''[[Wikipedia:NPOV|Neutral]]''''': Categorizations appear on article pages without annotations or referencing to justify or explain their addition; editors should be conscious of the need to maintain a neutral point of view when creating categories or adding them to articles. Categorizations should generally be uncontroversial; if the category's topic is likely to spark controversy, then a [[Wikipedia:Stand-alone lists|list article]] (which can be annotated and referenced) is probably more appropriate.
*: For example, a politician (not convicted of any crime) should not be added to a category of notable criminals.
*{{Anchor|Defining characteristics|Defining}}{{anchor|D|DEF|CATDEF}}{{Shortcut|WP:CAT#D|WP:CATDEF}} '''''[[WP:DEFINING|Defining]]''''': <section begin=DefiningDef /><section begin=DefiningFull />Defining characteristics of an article's topic are central to categorizing the article. A defining characteristic is one that [[WP:RS|reliable sources]] ''commonly'' and ''consistently'' refer to<ref>in declarative statements, rather than table or list form</ref> in describing the topic, such as the nationality of a person or the geographic ___location of a place.<section end=DefiningDef /> Articles should normally be included in the categories that are most closely related to the subject's defining characteristics.
*:For example, ''Italian'' and ''artist'' are defining characteristics of [[Caravaggio]], because virtually all reliable sources on the topic mention them, so that article is included in categories such as [[:Category:Italian Baroque painters]].<section end=DefiningFull />
* For [[Wikipedia:Overcategorization#Non-defining characteristics|non-defining characteristics]], editors should use their judgment to choose which additional categories (if any) to include.
*:For example, [[Caravaggio]] is included in the non-defining category of [[:Category:Deaths from sepsis]].
=== Naming conventions <span class="anchor" id="NC"></span> ===
{{For|the full category naming guidelines (including topic-specific naming conventions)|Wikipedia:Category names}}
{{#section:Wikipedia:Category names|NCCAT-ART}}
=== Categorizing articles about people ===
{{shortcut|WP:SEPARATE}}{{main|Wikipedia:Categorizing articles about people}}
{{see also|Category:People}}<section begin=CAAPEOPLE />
*For articles about people, categorize by characteristics of the person the article is about, <em>not</em> characteristics of the <em>article</em>: e.g., do not add <code><nowiki>[[Category:Biography]]</nowiki></code> to an article. [[Wikipedia:Categorization#Subcategorization|Sub-categories]] of [[:Category:Biography (genre)]] may legitimately contain articles about biographical <em>films</em> or biographical <em>books</em>, but should not contain articles about individual people. The <em>article</em> is a biography; the topic of the article{{snd}}the <em>person</em>{{snd}}is not.
*{{Anchor|SEPARATE}} Keep articles about people separate. Categories with a title indicating that the contents are people, should normally only contain biographical articles and lists of people, and perhaps a non-biographical main article, though this can also be added at the top of the category. This is for clarity and ease of use, and to preserve the integrity of [[:Category:People|category tree of people articles]].<section end=CAAPEOPLE />
=== Categorizing articles about works <span class="anchor" id="CATWORKS"></span><span class="anchor" id="CATFICTION"></span> ===
{{shortcut|WP:CATWORKS|WP:CATFICTION}}{{see also|Category:Creative works|Wikipedia:Category names#Works of art categories by subject}}
* Articles on fictional subjects should not be categorized in a manner that confuses them with real subjects. {{tl|Category see also}} is useful for interlinking examples of real-world and fictional phenomena.
* Individual [[:Category:Works by creator|works by a person]] should not be included in an [[#eponymous category]] but should instead be in a subcategory such as [[:Category:Novels by Agatha Christie]].
=== Categorizing list pages ===
{{see also|Category:Lists}}
If there are more than a few [[WP:Stand-alone lists|lists]] in a particular subject area, it may be appropriate to create a specific subcategory that contains only the list pages and no other types.
* For example, [[:Category:Countries]] contains the subcategory "[[:Category:Lists of countries]]", which in turn contains the list pages "[[List of Soviet Republics]]", and "[[List of countries by population]]".
When placing list pages in such a category, use a [[WP:SORTKEY|sort key]] to adjust the page title to exclude the starting words "List of", or all lists would appear under "L".
* For example, when adding List of Soviet Republics to the category, using <code><nowiki>[[Category:Lists of countries|Soviet Republics, List of]]</nowiki></code> and will make it be sorted in the S section.
=== Eponymous categories <span class="anchor" id="EPON"></span><span class="anchor" id="OCEPON"></span><span class="anchor" id="EPONYMOUS"></span><span class="anchor" id="Eponymous category"></span> ===
{{Shortcut|WP:EPON|WP:OCEPON|WP:EPONYMOUS}}{{see also|Category:Eponymous categories|Category:Wikipedia categories named after people}}
{{for|the overuse of the word "eponymous" on Wikipedia|WP:TITULAR}}
A category that covers exactly the same topic as an article is known as the '''eponymous category''' for that article (e.g. [[New York City]] and [[:Category:New York City]]; [[Mekong]] and [[:Category:Mekong River]]; [[Abraham Lincoln]] and [[:Category:Abraham Lincoln]]).
Eponymous categories should not be created unless enough directly related articles or subcategories exist. However, this should not be done simply to reduce the number of categories displayed in an article.
An eponymous category should have only the categories of its article that are relevant to the category's content. For example:
*Both [[New York City]] and [[:Category:New York City]] fit well in [[:Category:Cities in New York (state)]].
*The article [[New York City]] is in [[:Category:Populated places established in 1624]], but this category is not necessarily relevant to the content of [[:Category:New York City]], so it should not be used on the eponymous category.
==== Articles with eponymous categories <span class="anchor" id="CATMAIN"></span><span class="anchor" id="MAIN"></span> ====
{{Shortcut|WP:CATMAIN}}{{Redirect|WP:CATMAIN|the template|Template:Category main article}}
*The article itself should be a member of the eponymous category. It should be sorted with a space, so that it appears at the start of the category listing (see [[#Sort keys|§ Sort keys]] below).
*The article should be listed as the main article of the category using the {{tl|Category main article}} template.
*Articles with an eponymous category may be categorized in the broader categories that would be present if there were no eponymous category (e.g. the article [[France]] appears in both [[:Category:France]] and [[:Category:Countries in Europe]], even though the latter category is the parent of the former category). Editors should decide by consensus which solution makes most sense for a category tree. There are three options:
# Keep both the eponymous category and the main article in the parent category. This is used in [[:Category:Countries in Europe]] to allow that region's country articles to be navigated together.
# Keep just the child article. This is used in [[:Category:British Islands]], to prevent a loop.
# Keep just the eponymous category. This is used for [[:Category:Farmers]] in [[:Category:People by occupation]]. Such "''X'' by ''Y''" categories sometimes cover a limited navigational set, not a topic (see [[#Category tree organization|§ Category tree organization]] below), thus there is no logical article content.
If eponymous categories are categorized separately from their articles, it will be helpful to make links between the category page containing the articles and the category page containing the eponymous categories. The template {{Tl|Related category}} can be used for this. An example of this set-up is the linked categories [[:Category:American politicians]] and [[:Category:Wikipedia categories named after American politicians]].
== Categorizing draft pages <span class="anchor" id="DRAFTNOCAT"></span><span class="anchor" id="Draft"></span><span class="anchor" id="DRAFT"></span> ==
{{shortcut|WP:CATDRAFT|WP:DRAFTNOCAT}}{{Further|Wikipedia:Drafts#Preparing drafts}}
{{see also|Category:Wikipedia drafts}}
Drafts, no matter whether in the [[Wikipedia:Drafts|draft namespace]] or [[Wikipedia:Userspace|your userspace]], are not articles, and thus do not belong in content categories such as [[:Category:Living people|Living people]] or [[:Category:Biologists|Biologists]]. If you copy an article from mainspace to draftspace or your userspace and it already contains categories, then disable those categories. This can be done in any of the following four ways (but only the first two ways are recommended, as a disadvantage of the last two ways is that the categories would not be linked on the page):
* Wrapping them in {{tl|Draft categories}}:
:<syntaxhighlight lang="wikitext">
{{Draft categories|
[[Category:Living people]]
[[Category:Biologists]]
}}</syntaxhighlight>
* Inserting a colon character to [[Wikipedia:How to link to a category|link to each category]] (e.g. change <syntaxhighlight lang="wikitext" inline>[[Category:Biologists]]</syntaxhighlight> to <syntaxhighlight lang="wikitext" inline>[[:Category:Biologists]]</syntaxhighlight>)
* [[Wikipedia:Manual of Style/Hidden text|Commenting]] ({{tag|!--}}) them out (e.g. <syntaxhighlight lang="wikitext" inline><!--[[Category:Living people]] [[Category:Biologists]]--></syntaxhighlight> etc.).
* Wrapping them in {{tag|nowiki}} tags (e.g. <syntaxhighlight lang="wikitext" inline><nowiki>[[Category:Living people]] [[Category:Biologists]]</nowiki></syntaxhighlight> etc.).
After you move the draft into article space, remove the leading colons (or uncomment out the categories or remove the {{tag|nowiki}} tags) to re-enable the categories. If using the draft categories template, the categories will automatically work as normal in mainspace, but the template should be removed. The same system may be used in a new draft to list the categories it may have when moved to mainspace.
Two scripts are available to help with these tasks: [[User:DannyS712/Draft no cat]] and [[User:DannyS712/Draft re cat]].
== Categorizing project pages <span class="anchor" id="Non-article and maintenance categories"></span><span class="anchor" id="Maintenance categories"></span><span class="anchor" id="Administrative category"></span><span class="anchor" id="PROJCATS"></span> ==
{{Shortcut|WP:PROJCATS}}
===Wikipedia administrative categories ===
{{see|Wikipedia:Administration#Data structure and development|Wikipedia:Wikipedia namespace}}
{{see also|Category:Wikipedia administration}}
A distinction is made between two types of categories:
* Administrative categories{{snd}}intended for use by editors or by automated tools, based on features of the current state of articles, or used to categorize non-article pages.
* Content categories{{snd}}intended as part of the encyclopedia, to help readers find articles, based on features of the subjects of those articles.
Administrative categories include '''stub categories''' (generally produced by [[Wikipedia:Stub|stub]] templates), '''maintenance categories''' (often produced by [[Wikipedia:Template_index#Article-related_namespace|"cleanup" templates]] such as {{tl|cleanup}} and {{tl|fact}}, or those used for [[Wikipedia:Maintenance|maintenance]] projects), and '''categories of pages in non-article [[Wikipedia:Namespace|namespaces]]''', such as [[Wikipedia:WikiProject|WikiProject]] [[Wikipedia:Assessment|assessment]] [[:Category:Articles by quality|categories]] and [[:Category:Wikipedia policies and guidelines|categories]] holding [[Wikipedia:Policies and guidelines|Wikipedia policies and guidelines]].
Article pages should be kept out of administrative categories if possible. For example, the templates that generate WikiProject and assessment categories should be placed on talk pages, not on the articles themselves. If it is unavoidable that an administration category appears on article pages (usually because it is generated by a maintenance template that is placed on articles), then in most cases it should be made a '''hidden category''', as described in [[#Hiding categories|§ Hiding categories]] below.
There are separate administrative categories for different kinds of non-article pages, such as [[Wikipedia:Project namespace|project page]] categories, [[Wikipedia:Template|template]] categories, [[Wikipedia:Disambiguation page categories|disambiguation page categories]], etc.
In ''maintenance categories'' and other ''administrative categories'', pages may be included regardless of type. For example, in an error tracking category it makes sense to group templates separately, because addressing the errors there may require different skills compared to fixing an ordinary article. For sorting each namespace separately, see [[#Sort keys|§ Sort keys]] below.
=== Files <span class="anchor" id="FILECAT"></span><span class="anchor" id="Images"></span><span class="anchor" id="Files/images"></span> ===
{{shortcut|WP:FILECAT}}{{see|Wikipedia:Manual of Style/Images#Image description pages}}
Category tags should be added to [[Help:Files|file]] pages of files that have been uploaded to Wikipedia. When categorized, files are not included in the count of articles in the category, but are displayed in a separate section with a thumbnail and the name for each. A category can mix articles and images, or a separate file/image category can be created. A file category is typically a subcategory of the general category about the same subject, and a subcategory of the wider category for files, [[:Category:Wikipedia files]]. To categorize a new file when uploading, simply add the category tag to the [[Help:Edit summary#File upload summary|upload summary]].
Freely licensed files should be uploaded to, and categorized on, [[WP:COMMONS|Wikimedia Commons]], instead of uploading and categorizing on Wikipedia. Existing freely licensed files should usually be moved from Wikipedia to Commons, with a mirror page automatically remaining on Wikipedia. (For an example of one such mirror page, see [[:File:Niederwald memorial 2.JPG|here]].) Categories should not be added to these Wikipedia mirror pages, because doing so creates a new Wikipedia page that is subject to [[WP:SD#F2|speedy deletion]]. Exceptions to this principle are made for mirror pages of images that are nominated as [[Wikipedia:Featured pictures|featured pictures]] and for those that appear on the Wikipedia [[Main Page]] in the [[:Template:Did you know|Did You Know?]] column.
Images that are used in Wikipedia that are [[Wikipedia:Non-free content|non-free or fair use]] should not appear as thumbnail images in categories. To prevent the thumbnail preview of images from appearing in a category, <nowiki>__NOGALLERY__</nowiki> should be added to the text of the category. In such cases, the file will still appear in the category, but the actual image preview will not.
=== Templates <span class="anchor" id="TEMPLATE"></span><span class="anchor" id="TEMPLATES"></span><span class="anchor" id="TEMP"></span><span class="anchor" id="T"></span> ===
{{shortcut|WP:CAT#T}}{{See also|Template:Documentation}}
[[Wikipedia:Template namespace|Templates]] are not articles, and thus do not belong in ''content categories''. It is however a recommendation to place them in '''template categories''' – subcategories of [[:Category:Wikipedia templates]] – to assist when looking for templates of a certain type. For example, [[:Template:Schubert string quartets]] is categorized under [[:Category:String quartets by composer navigational boxes]], which should be a subcategory of [[:Category:Music navigational boxes]] (type) but [[:Template:Schubert string quartets]] should ''not'' be categorized under [[:Category:Franz Schubert]] or [[:Category:String quartets]] (content).
Pages using a template should rarely be placed in the same categories as the template itself. To ensure this separation, the category for the template should be placed on the template's documentation page, normally after the two pipes in a <syntaxhighlight lang=wikitext inline><includeonly>{{Sandbox other||...}}</includeonly></syntaxhighlight> block. Because template documentation is rarely [[Wikipedia:Protection policy|protected]], template categorization can be modified by all editors even when the template code itself is protected from editing by most editors. When there is no documentation page, the category for the template may be placed at the bottom of the template itself, within a {{tag|noinclude}} block. There should be no spaces or new lines between the last part of the template proper and the opening {{tag|noinclude|o}} tag.
===User pages <span class="anchor" id="Categorizing user pages"></span><span class="anchor" id="USER"></span><span class="anchor" id="USERS"></span><span class="anchor" id="USERNOCAT"></span> ===
{{shortcut|WP:CAT#USER|WP:USERNOCAT}}{{Further|Wikipedia:User categories|Wikipedia:User pages#Categories, templates that add categories, and redirects}}
[[Wikipedia:User pages|User pages]] are not articles and thus do not belong in ''content categories'' such as [[:Category:Living people|Living people]] or [[:Category:Biologists|Biologists]]. Similarly, [[#Draft]] versions of articles should be kept out of content categories. Also, do not [[Help:Transclusion|transclude]] articles into your user pages, as this will result in the page being included in all the article's categories.
However, user pages ''can'' be placed in '''user categories''' – subcategories of [[:Category:Wikipedians]], such as [[:Category:Wikipedian biologists]] – which assist collaboration between users. And certain [[WP:SP|user sub-pages]] that are non-article drafts, are permitted in [[#PROJCATS|project categories]], like [[:Category:User essays]].
A list of article-space categories with user pages, is maintained at [[WP:Database reports/Polluted categories|Database reports/Polluted categories]].
==Categorization using templates <span class="anchor" id="TEMPLATECAT"></span><span class="anchor" id="TCAT"></span> ==
{{shortcut|WP:TEMPLATECAT|WP:TCAT}}
Many [[Wikipedia:Template messages|templates]] include category declarations in their transcludable text, for the purpose of [[:Category:Tracking categories|placing the pages containing those templates into specific categories]]. This technique is very commonly used for populating certain kinds of administration categories, including stub categories and maintenance categories. See [[Template:Infobox roller coaster]] for an example that only adds a category by manufacturer if it exists, and otherwise uses a hidden category.
However, it is recommended that articles not be placed in ordinary ''content'' categories using templates in this way. There are many reasons for this: editors cannot see the category in the wikitext; removing or restructuring the category is made more difficult (partly because automated processes will not work); inappropriate articles and non-article pages may get added to the category; [[#Sort keys|sort keys]] may be unavailable to be customised per category; and ordering of categories on the page is less controllable.
When templates are used to populate administration categories, ensure that the code cannot generate nonsensical or non-existent categories, particularly when the category name depends on a parameter. Also, see [[Wikipedia:Category suppression|Category suppression]] for ways of keeping inappropriate pages out of template-generated categories.
Category declarations in templates often use <code><nowiki>{{PAGENAME}}</nowiki></code> as the sort key, because this overrides any DEFAULTSORT defined on the page.
{{anchor|Redirected categories|CATRED|Redirects}}
===Redirecting categories ===
{{redirect|WP:CAT-R|the guideline on categorizing page redirects|Wikipedia:Categorizing redirects}}
{{Redirect|WP:CATRED|the guideline on red-linked categories|WP:REDNOT}}{{shortcut|WP:CATRED}}
{{for|an essay on this topic|Wikipedia:Category redirects that should be kept}}
{{see also|Category:Wikipedia soft redirected categories}}
<section begin=CATREDIRECT />Do {{em|not}} create inter-[[Help:Category|category]] redirects by adding <code><nowiki>#REDIRECT [[target]]</nowiki></code> to a category page. Unlike when [[Help:How to move a page|renaming articles]], categories cannot be [[Help:Redirect|redirected]] using "hard" redirects. Articles added to a "redirected" category will not show up in the target category. And since redirected categories do not become "[[Wikipedia:Red link|red links]]", editors won't be aware even when they add an article to a redirected category.<ref>For an attempt to fix this issue in [[MediaWiki]], {{crossref|pw=y|see {{Phab|T5311}}}}.</ref>
Instead, a form of "'''[[Wikipedia:Soft redirect|soft redirect]]'''" may be used in limited circumstances. You can create a [[Wikipedia:Category redirects|category redirect]] by adding {{tlx|Category redirect|target}} to the category page. [[Wikipedia:Bots|Bots]] patrol these categories and move articles to the "target" of the redirect.
If you need to add an [[WP:RCAT|rcat]] to a {{t|Category redirect}}, use the template's second parameter. For example, <syntaxhighlight inline lang="wikitext">{{Category redirect | Years of the 19th century in Ceylon | {{R from category navigation}} {{R from template-generated category}} }}</syntaxhighlight>
Category redirects are [[WP:COSTLY|costly]]. While placing a page in a category redirect is not a ''big'' problem, it <em>is</em> a problem. There are [[Wikipedia:Category redirects that should be kept#Category redirects that might be useful|plenty of helpful uses of category redirects]], but category redirects are not as [[WP:CHEAP|cheap as regular redirects]]. Links to article redirects are [[WP:NOTBROKEN|not broken]]: i.e. click on the link and you are automatically redirected to its target. However, links to category redirects <em>are</em> broken and need to be fixed, except when resolved by a template (i.e. the template generates categories using a pattern, and some of the resulting category names are intentionally resolved by the use of {{tl|resolve category redirect}} within the template, as in the Ceylon example above). Placing a page into a category redirect makes it show up in the category redirect — not its target — until a bot comes along and fixes the link.<section end=CATREDIRECT />
{{anchor|DISAMBIGCAT}}{{shortcut|WP:DISAMBIGCAT}}If the category was renamed because it is ambiguous, and categories exist for two or more meanings, then create a category [[Wikipedia:Disambiguation#Disambiguation pages|disambiguation page]] at the old name, using {{tl|category disambiguation}}. See also [[:Category:Disambiguation categories]]
{{OOUI icon|information}} ''Note:'' usually only do this at an unused category name which is ambiguous, e.g. [[:Category:Lewis]]. If an ambiguous name is used for an active category because it is clearly the [[WP:PRIMARYTOPIC]], and there are only 1 or 2 others, then use a hatnote like the one at [[:Category:Lewes]]. For longer lists, we can also create pages such as [[:Category:Bedford (disambiguation)]].
{{anchor|HIDDENCAT}}
===Hiding categories===
{{Shortcut|WP:HIDDENCAT}}{{see also|mw:Help:Categories#Hidden categories}}
In cases where, for technical reasons, administration categories appear directly on articles rather than talk pages, they should be made into '''hidden categories''', so that they are not displayed to readers. This rule does not apply to [[Wikipedia:Stub|stub]] categories or "uncategorized article" categories – these types are ''not'' hidden.
To hide a category, add the template {{tlx|Wikipedia category|<nowiki>hidden=yes</nowiki>}} to the category page (the template uses the [[Wikipedia:Magic word|magic word]] <code><nowiki>__HIDDENCAT__</nowiki></code>). This also places the page in [[:Category:Hidden categories]].
A logged-in user may elect to view all hidden categories, by checking "Show hidden categories" on the "Appearance" tab of [[Special:Preferences|Preferences]]. Notice that "hidden" parent categories are never in fact hidden on category pages (although they are listed separately).
Hidden categories are listed at the bottom when previewing. All users of the desktop version can see hidden categories for a page by clicking "Page information" under "Tools" in the left pane, or by editing the whole page with the source editor.
{{anchor|TREE}}
==Category tree organization==
{{Shortcut|WP:CAT#TREE}}{{see also|Category:Contents|Tree structure|Tree (data structure)}}
[[File:Category-diagram.png|thumb|300px|Partial view of Wikipedia's category system from 2007. Arrows point from category to subcategory.]]
Categories are organized as overlapping "[[Tree structure|trees]]", formed by creating links between inter-related categories (in mathematics or computer science this structure is called <!---Wikipedia's categories don't have unique joins or meets---a lattice or---> a [[partially ordered set]]).
There is one top-level category: [[:Category:Contents]]. All other categories are subcategorized below this category.
{{Gallery
|title=
|File:Binary tree structure.svg
|A [[tree structure]] showing the possible hierarchical organization of an encyclopedia
|File:Bureaucracy(medium).svg
|
|File:Tree product pract.svg
|An item may belong to several subcategories of a parent category (as pictured).
|}}
{{anchor|SUBCAT|PARENTCAT}}
=== Subcategorization ===
{{shortcut|WP:SUBCAT|WP:PARENTCAT}}
If logical membership of one category implies logical membership of a second category (an [[is-a]] relationship), then the first category should be made a subcategory (directly or indirectly) of the second category (the "parent" category). Any category may potentially contain (or "branch into") subcategories.
* For example, A is said to be a ''parent category'' of B when B is a ''subcategory'' of A.) <ref>Mathematically speaking, this means that the system approximates a [[directed acyclic graph]].</ref>
When making one category a subcategory of another, ensure that the members of the subcategory really can be expected (with possibly a few exceptions) to belong to the parent also.
*For example, [[:Category:Cities in France|Cities in France]] is a subcategory of [[:Category:Populated places in France|Populated places in France]], which in turn is a subcategory of [[:Category:Geography of France|Geography of France]].
A subcategory may potentially have two or more parent categories.
*For example, [[:Category:British writers]] would be in both [[:Category:Writers by nationality]] and [[:Category:British people by occupation]].
If two categories are closely related but are not in a subset relation, then links between them can be included in the [[#CATDESC|category description]] of the category pages.
Category [[Chain (ordered set)|chains]] formed by parent–child relationships should never form closed loops;<ref>This condition can be formulated in terms of [[graph theory]] as follows: the directed graph that has the categories as vertices and the parent-child relationships as edges should be ''[[directed acyclic graph|acyclic]]''.</ref> that is, no category should be contained as a subcategory of one of its own subcategories.{{#tag:ref|There is an exception to this for maintenance purposes. For example, [[:Category:Hidden categories]] is a direct subcategory of itself and of [[:Category:Wikipedia extended-confirmed-protected pages]] and [[:Category:Container categories]], each of which is a direct subcategory of [[:Category:Hidden categories]].}}
{{anchor|DIFFUSE}}
===Diffusing large categories===
{{Shortcut|WP:DIFFUSE}}{{redirect|WP:DIFFUSE|conflicts|Wikipedia:Diffusing conflict}}
Although there is no limit on the size of categories, a large category will often be broken down ("diffused") into smaller, more specific subcategories. For example, [[:Category:Rivers of Europe]] contains no articles about specific rivers directly; they are all in subcategories.
{{anchor|Metacategories|META}}A category may be diffused using several coexisting schemes; for example, [[:Category:Albums]] is broken down by artist, by date, by genre etc. '''Metacategories''' may be created as ways of organizing schemes of subcategories. For example, the subcategories called "''Artistname'' albums" are not placed directly into [[:Category:Albums]], but into the metacategory [[:Category:Albums by artist]], which itself appears in Category:Albums. (See [[:Category:Categories by parameter]])
It is possible for a category to be only partially diffused—some members are placed in subcategories, while others remain in the main category.
Information about how a category is diffused may be given on the category page. Categories which are intended to be fully broken down into subcategories can be marked with the {{tl|category diffuse}} template, which indicates that any pages which editors might add to the main category should be moved to the appropriate subcategories when sufficient information is available. (If the proper subcategory for an article does not exist yet, either create the subcategory or leave the article in the parent category for the time being.)
To suggest that a category is so large that it ought to be diffused, or substantially diffused, into subcategories, you can add the {{tl|overpopulated category}} template to the category page.
{{anchor|NON-DIFFUSE|NONDIFFUSE|ALLINCLUDED|DUPCAT}}
===Non-diffusing subcategories===
{{Shortcut|WP:CAT#NON-DIFFUSE|WP:ALLINCLUDED|WP:DUPCAT}}
Not all subcategories serve the "diffusion" function described above; some are simply subsets which have some special characteristic of interest, such as [[:Category:Best Actor Academy Award winners|Best Actor Academy Award winners]] as a subcategory of [[:Category:Film actors|Film actors]]. They provide an exception to the general rule that pages are not placed in both a category and its subcategory: there is no need to take pages out of the parent category ''purely'' because of their membership of a non-diffusing subcategory. (Of course, if the pages also belong to other subcategories that do cause diffusion, then they will not appear in the parent category directly.)
Non-diffusing subcategories should be identified with a template on the category page:
* The {{Tl|Non-diffusing subcategory}} templates should be used for subcategories that are non-diffusing, like {{cl|American novelists of Asian descent}}.
* The {{Tl|All included}} can be used for categories where all child articles of a certain type are in the parent, like {{cl|Presidents of the United States}} or {{cl|Mountains of Switzerland}}.
Subcategories defined by gender, ethnicity, religion, and sexuality should almost always be non-diffusing subcategories to prevent [[Other (philosophy)|othering]]. The [[Wikipedia:Categorizing articles about people]] guideline outlines the rules on these categories in more detail.
Note that some categories can be non-diffusing on some parents, and diffusing on others. For example, {{cl|British women novelists}} is a non-diffusing subcategory of {{cl|British novelists}}, but it is a diffusing subcategory of {{cl|Women novelists by nationality}}.
{{Anchor|Sort order|SORTKEY}}
==Sort keys==
{{shortcut|WP:SORTKEY}}{{redirect|WP:Sorting|sorting of tables|Help:Sortable tables}}
'''Sort keys''' are sometimes needed to produce a correct ordering of member pages and subcategories on the category page. For the mechanics, see {{section link|Help:Category#Sorting category pages}}.
Categories of people are usually sorted by last name rather than first name, so "last name, first name" sort keys are used (as in "Washington, George"). There are many other rules for sorting people's names; for more information, see [[WP:NAMESORT]].
Other sort key considerations (in no particular order):
* In English Wikipedia, sort order merges (ignores) case and diacritics. For example, "Baé", "Båf", "BaG" would be sorted in that order.<ref>In 2016, English Wikipedia's category collation was changed to "uca-default", which is based on the [[Unicode collation algorithm]] (UCA). The most noticeable difference is that UCA groups characters with diacritics with their non-diacritic versions. See {{Section link|Wikipedia talk:Categorization/Archive 16#OK to switch English Wikipedia's category collation to uca-default?}} and {{Section link|Wikipedia:Village pump (technical)/Archive 149#Sorting in categories unreliable for a few days}}.</ref>
* The main article/s of a category, if existent, should get sorted with a space as key so that it/they appear(s) at the very top of the category. Example: <code><nowiki>[[Category:Example| ]]</nowiki></code> Those articles are typically homonymous or at least synonymous to their category.<!--generally shouldn't exceed 3 articles; most of the time it should be a single one--> Furthermore, other general articles that are highly relevant to the category should be sorted with an asterisk as key so that they also appear at the top of a category but beneath the main article/s. Example: <code><nowiki>[[Category:Example|*]]</nowiki></code> Those articles are typically called "History of example", "Types of example", "List of example" or similar.<!--generally shouldn't exceed 5 articles; most of the time it should be a single one-->
* [[Article (part of speech)|Leading articles]]—a, an, and the—are among the most common reasons for using sort keys, which are used to transfer the leading article to the end of the key, as in <nowiki>{{DEFAULTSORT:Lady, The}}</nowiki>. Please also apply these sort keys to deliberate misspellings of these words, ''e.g.'' "da" or "tha" for "the", as well as foreign language leading articles, such as "el" or "der" (but beware of non-article words that have the same spelling, e.g. that translate as "at" or "one"). However, leading articles in foreign-language-derived names which are no longer translated in English are not subject to this rule; e.g. the sort key for [[El Paso]] should be left as the default value (i.e. no <nowiki>{{DEFAULTSORT}}</nowiki> required).
* Spell out abbreviations and characters used in place of words so that they can be found easily in categories. For example, the sort key for [[Mr. Bean]] should be <nowiki>{{DEFAULTSORT:Mister Bean}}</nowiki> and [[Dungeons & Dragons]] should be sorted <nowiki>{{DEFAULTSORT:Dungeons and Dragons}}</nowiki>. An exception is the times sign (×) as in "Men's 4 × 100 metre" relay; use the letter x in this case.
* Landforms (and similar) that have noun prefixes such as [[Isle of Mull]] should have the noun sorted after as <nowiki>{{DEFAULTSORT:Mull, Isle of}}</nowiki>. However, this isn't usually done for settlements and administrative divisions; for example, while [[Isle of Wight]] uses <nowiki>{{DEFAULTSORT:Wight, Isle of}}</nowiki>, the categories for the county/district are sorted "Isle of Wight". Also for settlements such as [[Isle of Wight, Virginia]] the prefix isn't moved.
* Hyphens, apostrophes and periods/full stops are the only punctuation marks that should be kept in sort values. The only exception is the apostrophe in names beginning with ''O{{'}}'', which should be removed. For example, [[Eugene O'Neill]] is sorted <nowiki>{{DEFAULTSORT:Oneill, Eugene}}</nowiki>. All other punctuation marks should be removed. (Commas can be added when re-ordering words, as in the previous example.)
* Entries containing numbers sometimes need special sort keys to ensure proper numerical ordering. For example, IX comes before V in alphabetical order, so [[Pope John IX]] might have a sort key "John 9". To get the correct sort order zero padding may be required, thus the ''actual'' sort key in this case is "John 09" this ensures that [[Pope John IX]] sorts before [[Pope John X]] – if we ever get to the hundredth Pope John, we would need to use three digits "John 009". Also note that numbers which include separators (such as commas or periods) will only have the part of the number before the first separator considered by the sorting algorithm. So [[10,000 Maniacs]] might have a sort key "10000 Maniacs". It is important to stick to the same system for all similar entries in a given category.
* Systematic sort keys are also used in other categories where the logical sort order is not alphabetical (for example, individual month articles in year categories such as [[:Category:2004]] use sort keys like "*2004-04" for April). Again, such systems must be used consistently within a category.
* In some categories, sort keys are used to exclude prefixes that are common to all or many of the entries, or are considered unimportant (such as "List of" or "The"). For example, in [[:Category:2004]] the page [[2004 in film]] would have the sort key "Film", and in [[:Category:2004 in Canada]] the page [[2004 Canadian federal budget]] would have the sort key "Federal Budget".
* Use other sort keys beginning with a space (or an asterisk or a plus sign) for any "List of ..." and other pages that should appear ''after'' the key article and ''before'' the main alphabetical listings, including "Outline of" and "Index of" pages. The same technique is sometimes used to bring particular subcategories to the start of the list.
:Sort order of characters ''before'' numbers and Latin alphabet (0–9, A–Z) is (partial list):
:'''<code>! " # $ % & ' ( ) * + , - . / 0 9 : ; < = > ? @ [ \ ] ^ _ ` A Z a z { | } ~ É é —</code>'''
:''See also:'' [[:Meta:Help:Sorting#Sort modes]] for more information.
* Sort keys may be prefixed with [[Greek letters]] to place entries ''after'' the main alphabetical list. The following letters have special meaning by convention:
** "[[Σ]]" (capital sigma) is used to place [[Wikipedia:Stub|stub]] categories at the end of subcategory lists. ("µ" ([[Mu (letter)|mu]]) was previously used, but the capital version "Μ" was confusing.)
** "[[β]]" (beta, displays as capital, "Β") is for [[WP:*|barnstars]].
** "[[Δ]]" (delta) is for [[Wikipedia:Documentation|documentation]], where sorting by Latin D is undesirable.
** "[[ι]]" (iota, displays as "Ι") is for [[Wikipedia:Images|Wikipedia images]].
** "[[ρ]]" (rho, displays as "Ρ") is for [[Wikipedia:Portal|portals]].
** {{anchor|Tau}}"[[τ]]" (tau, displays as "Τ") is for [[Help:Template|templates]]. Keep in mind, template categories should not be added to content categories per [[WP:CAT#T]].
** "[[υ]]" (upsilon, displays as "Υ") for [[WP:Userbox|user templates]].
** "[[ω]]" (omega, displays as "Ω") is for [[WikiProject]]s.
*:Similar to the handling of Latin letters, if the sort key is or begins with a lower case Greek letter, then the capital Greek letter will be displayed in headings on category pages. Items whose sort keys begin with lowercase letters will appear beneath corresponding capital letters. Several of these resemble Latin letters B, I, P etc., but they will sort after [[Z]].
*:{{OOUI icon|information}} ''Note:'' Not all of these types are suitable for inclusion in ''content categories''. For one-type categories, such as ''template categories'', Greek letter grouping is not useful.
* If a page is to be given the same sort key in all or several of its categories, the <code><nowiki>{{DEFAULTSORT}}</nowiki></code> [[Help:Magic words|magic word]] should be used. Per [[MOS:ORDER]], this is placed just before the list of category declarations. Default sort keys are sometimes defined even where they do not seem necessary—when they are the same as the page name, for example—in order to prevent other editors or automated tools from trying to infer a different default.
{{anchor|BADCAT|CFD|CfD}}
==Inappropriate categorization==
{{shortcut|WP:BADCAT}}
Anyone may edit an article and remove a questionable categorization. If an article has an "incorrect" or "inappropriate" category, remove that category from the article, and replace it (if applicable) with a more correct category.
Even if an article may occupy the grey areas of a category's inclusion criteria, that is not a valid reason to keep the article in a category. If a particular article does not fit the inclusion criteria of a category, ''then the article simply should not be added to it''.
If categorization of any particular page is [[WP:DR|disputed]], please [[WP:CON|discuss]] the categorization on the [[WP:TALK|talk page]] of the page in question. If the category seems reasonable, but questionable in some cases, consider whether you can solve (part of) the problem by writing a clearer [[#Category description]].
If you have a proposal for a better name for the category or for a wider re-arrangement of the categorization scheme; or if you have a concern that may apply to several members of the category (such as if the category violates one or more sections on this page, [[Wikipedia:Categorizing articles about people]], [[Wikipedia:Overcategorization]], or other Wikipedia [[Wikipedia:policies and guidelines|policies and guidelines]]), you can participate in, or post a new, discussion about the category.
Category talk pages are not always widely [[Help:Watchlist|watched]]. Consider whether you can [[Wikipedia:Canvassing#Appropriate_notification|invite more potentially interested people]] to take part in a discussion, such as by discussing it at a relevant [[Wikipedia:WikiProject|WikiProject]], or at [[Wikipedia:WikiProject Categories]]. Another option could be to nominate the category for discussion at [[Wikipedia:Categories for discussion]], or if the [[Wikipedia:Category names|category name]] has an obvious typographical error, you can list it for speedy renaming at [[Wikipedia:Categories for discussion/Speedy]].
''See [[Wikipedia:Categories for discussion/How-to]] for instructions on how to use the templates for: '''deletion''' ({{tl|cfd}}), '''renaming''' ({{tl|cfr}}), or '''merging''' ({{tl|cfm}}).''
If you are in a content dispute, see [[Wikipedia:Dispute resolution]] for what to do next.
==Category cleanup templates==
* Article with insufficient categories
** {{Tl|Improve categories}} template indicates that the article needs additional or more specific categories. It is recommended that this template be placed at the ''bottom'' of the page, where readers will look for the categories.
* Article with too many categories
** Use {{Tl|Recategorize}} template when there are too many categories. Put this template ''on the top'' of articles.
* Category unknown
** If you're not sure where to categorize a particular page, add the {{Tl|uncategorized}} template to it, and other editors (such as those monitoring [[Wikipedia:WikiProject Categories/uncategorized]]) will help find appropriate categories for it.
==See also==
* [[Wikipedia:Categorization dos and don'ts]] (information page summarizing key points of this guideline)
* [[Wikipedia:Category suppression]]
* [[Wikipedia:WikiProject Categories]]
* [[m:Association of Categorist Wikipedians]]
* [[m:Help:Sorting]]
* [[:Category:Wikipedia essays about categorization]]
* [[Wikipedia:FAQ/Categorization]]
* [[Help:Gadget-Cat-a-lot]], script for moving subcategories between categories
* [[Wikipedia:Maintenance]]
===For browsing===
* [[Wikipedia:PetScan]] (formerly CatScan)
* [[Wikipedia:Classification]] (category tree jumping)
* [[Wikipedia:Category intersection]] (ability to find articles that are in more than one category)
* [[Special:Categories]] (lists all existing categories alphabetically)
* [[Special:CategoryTree]]
* [[:Category:Wikipedia categories]]
===For maintenance===
* [[Special:MostLinkedCategories]]
* [[Special:
* [[Special:
* [[Special:
* [[Special:WantedCategories]]
* [[Wikipedia:Category combinatorics]]
* [[Wikipedia:Database reports#Categories]]
* [[Template:Category link with count]]
* [[Template:Wikipedia categorization navbox]]
==Notes==
{{reflist}}
{{Wikipedia policies and guidelines}}
[[Category:Wikipedia categorization| ]]
[[Category:Wikipedia how-to]]
[[Category:Wikipedia project content guidelines]]
[[Category:Wikipedia Manual of Style (related guidelines)]]
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