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This article provides guidelines on creating and organizing categories.
==When to use categories==
Categories (along with other features like cross-references, lists, and infoboxes) help users find information, even if they don't know that it exists or what it's called.
Every page in the article namespace should belong to at least one category. Categories should be major topics that are likely to be useful to someone reading the article.
:'''Article:''' [[Michael Jackson]]
:'''Useful category:''' [[:Category:Pop singers]]
:'''Not useful:''' ''Category:Musicians whose first name starts with M''
Questions to ask to determine whether it is appropriate to add an article to a category:
*If the category does not already exist, is it possible to write a few paragraphs or more on the subject of the category, explaining it?
*If you go to the article from the category, will it be obvious why the article was put in the category? Is the category subject prominently discussed in the article?
If the answer to either of these questions is no, then the category is probably inappropriate. Note that it is always appropriate to add articles to categories that fit into well established taxonomies. For example, every article about a musical album is categorized in some <nowiki>[[Category:Artistname albums]]</nowiki> category, which is in turn categorized in [[:Category:Albums by artist]].
==Guidelines==
{{Meta}}
===Some general guidelines===
#Categories are mainly used to browse through similar articles. Make decisions about the structure of categories and subcategories that make it easy for users to browse through similar articles.
#An article will often be in several categories. Restraint should be used as categories become less effective the more there are on any given article.
#Articles should not usually be in both a category and its subcategory. For example [[Golden Gate Bridge]] is in [[:Category:Suspension bridges]], so it should not also be in [[:Category:Bridges]]. However there are occasions when this guideline can and should be ignored. For example, [[Robert Duvall]] is in [[:Category:Film actors]] as well as its subcategory [[:Category:Best Actor Academy Award winners]]. See #5 for another exception. For more about this see '''[[Wikipedia:Categorization/Categories and subcategories]]'''
#Check to see where siblings of the article reside. If there are few if any articles in a category, the article probably belongs in one of the subcategories.
#Articles should be placed in categories with the same name. However, the article and the category do not have to be categorized the same way. The article can also be placed in categories populated with similar articles. The category can be put into categories populated with similar subcategories. For an example of this see [[George W. Bush]] and [[:Category:George W. Bush]].
#There are often occasions when articles might ideally be moved from a category to two or more of its subcategories, but not all of the subcategories exist. In such cases consider creating the additional subcategories, but if you decide not to do so, leave the articles in the parent category for the time being.
#Bend the rules above when it makes sense, but only if no other solution can be found.
#Categories appear without annotations, so be careful of [[NPOV]] when creating or filling categories. Unless it is self-evident and uncontroversial that something belongs in a category, it should not be put into a category. A list might be a better option.
#If you don't know where to put an article don't worry about it. Instead of adding a category, use the {{tl|uncategorized}} tag to bring attention to the article. Editors who love to categorize articles will find a good home for your article.
===Categories vs. Lists vs. Info boxes===
For alternative methods of grouping articles, and the circumstances in which they should be used, see [[Wikipedia:Categories, lists, and series boxes]].
===Categories applied to articles on people===
A separate wikipedia page [[Wikipedia:Categorization of people]] was created to help you in designing, applying and checking categories that are used for articles on people.
===Categories do not form a tree===
Each Wikipedia article can appear in more than one category, and each category can appear in more than one parent category. Multiple categorization schemes co-exist simultaneously. In other words, categories do not form a strict hierarchy or [[tree structure]], but a more general [[directed acyclic graph]] (or close to it; see below).
Nevertheless, parts of the category graph will be tree-like, and it may be convenient to think of parts of the category graph as being like multiple overlapping trees. When applying the guidelines above, consider each tree to be independent of the overlapping trees. A person browsing through a hierarchy should find every article that belongs in that hierarchy. This can lead to a good deal of debate as to what the hierarchies actually are. To clarify the structure of the hierarchy and help people browse through it, you can add a classification to each category. For more about this, see [[Wikipedia:Classification]].
===Cycles should usually be avoided===
Although the MediaWiki software does not prevent [[cycle (graph theory)|cycles]] (loops), these usually should be avoided. Cycles can be confusing to some readers, they can challenge some automated searching processes and they can grow quite large. For example, in January 2006 a 22-member category cycle was discovered and eliminated.
However, acceptable loops also exist. Self-referencing systems such as the [[meta-]] fields naturally create cycles that provide many examples. This type of cycle involves making a category one of its own subcategories. A real-world example of a self-referencing system is “education about education,” such as:
:Classification: [[:category:Education|Education]]: [[:category:Social sciences|Social sciences]]: [[:category:Academic disciplines|Academic disciplines]]: [[:category:Academia|Academia]]: [[:category:Education|Education]]: ...
Another type of cycle involves making two categories subcategories of each other. Loops such as these can be avoided by linking the categories manually to each other by adding "See also:[[:Category:Foo]]" to each category page. For an example of this see [[:Category:World Trade Center]] and [[:Category:September 11, 2001 attacks]].
==How to put an article into categories==
{{Style}}
Adding an article to a category is as simple as editing the article and adding a link to the category. For instance, to add ''[[Felis silvestris catus]]'' article to the "fluffy creatures" category, you would edit the article and enter <tt><nowiki>[[Category:Fluffy creatures]]</nowiki></tt> at the bottom, but ''before'' [[Wikipedia:Interlanguage links|interlanguage links]]. The appeal of categories is that unlike lists, they update themselves automatically, and you don't have to edit the category to add an article to it. However, categories are not a substitute for [[Wikipedia:list|list]]s, and you will find that many articles belong to both lists and categories.
When adding an article to a category, or creating categories, one should be careful to use the correct categories and subcategories. Horizontal categorization, directly below, refers to placing an article in the correct category while vertical categorization refers to placing an article in the correct ''sub''category.
When assigning an article into categories, try to be thorough in a
"horizontal" sense. The topic may be associated with a geographic
area, a historical period, an academic subfield, a certain type of
thing (like a food or an ornament), and/or a special interest topic
(like [[:Category:Roman Empire|Roman Empire]] or [[:Category:LGBT|LGBT]]). You might need to poke around the
category hierarchy a bit to find the right place. Try searching for
articles similar to the article you are categorizing to get ideas or
to find the most appropriate place.
In the "vertical" dimension, Wikipedia has traditionally been more frugal, placing articles only in the most specific categories they reasonably fit in. Thus, if there is a [[:Category:American film actors]], [[John Wayne]] would go there and not in [[:Category:Film actors]] or [[:Category:American actors]]. However, there is a school of thought that argues that, because different users may be interested in different categories, and because placing articles in multiple categories takes up minimal additional space, in some cases one should place articles in all the categories that apply.
<!-- For example, [[Elizabeth_II_of_the_United_Kingdom|Queen Elizabeth]] should not be listed directly under People, but 'Category:Monarchs of the United Kingdom' might be a good place for her. We know that all Queens of the United Kingdom qualify as Famous Britons and as Royalty, and all of those folks qualify as People. Sometimes there's a good reason to assign an article to two categories, one of which is a direct or indirect subcategory of another. For a well-argued case study, see [[John Lennon]]. -->
For more about this see '''[[Wikipedia:Categorization/Categories and subcategories]]'''
==How to create categories==
Creating a category is as simple as adding a link to a category that doesn't yet exist. For instance, to create the "fluffy creatures" category, you would edit an article and enter <tt><nowiki>[[Category:Fluffy creatures]]</nowiki></tt> the same way as adding it to any other category. The <tt>Category:Fluffy creatures</tt> will automatically be created when the edit is saved.
===Category naming===
Categories follow the same general naming conventions as articles, for example do not capitalize regular nouns. For specific conventions related to categories, see [[Wikipedia:Naming conventions (categories)]].
Whatever categories you add, make sure they do not implicitly violate
the [[WP:NPOV|neutral point of view policy]]. If the nature of something is in dispute (like whether or not it's fictional or scientific or whatever),
you may want to avoid labelling it or mark the categorization as
disputed. Most categorizations are pretty straightforward, though.
===Look before you leap===
Before creating a category, look to see if one already exists. The best way to do this is to first add the category to your article but preview before saving. If the category appears in blue at the bottom of the page, the category already exists. If it is in red, then you will be creating a new category. Check the capitalization of the category name. For any red categories, you should look for categories with similar names before creating a new category. One way to do this is to think of the parent category for the new category. Search for it and then look at the subcategories in the parent. You may find that a category already exists that is similar to the one you are thinking about creating.
You may see some inconsistencies when first creating the category: it may alternate between appearing empty and appearing with your first additions. It will probably correct itself in a few minutes. Note that, although "uncreated" categories ''will'' correctly list articles that have been assigned to them, the category page itself does not exist until it is manually created. The easiest way to create the category page is to follow the red category link from your article and create a new category page with a parent category and a category description as explained in the next section.
==How to create subcategories==
Create subcategory pages by putting the name of the parent category on a category page that you would like to be the subcategory. Child categories (subcategories) are created by putting <nowiki>[[Category:</nowiki>''parent_category_name''<nowiki>]]</nowiki> '''on the lower-level category pages'''. For example, on a (sub)category page called ''category:Roses'' you put <nowiki>[[Category:Flowers]]</nowiki>, Roses becomes a subcategory of Flowers.
When writing the description for a category try to give it at least two parent categories. For example, [[:Category:British writers]] should be in both [[:Category:Writers by nationality]] and [[:Category:British people]]. A few categories do only merely subdivide their parent category, but unless the parent category has many potential articles under it, or many potential subdivisions, if you can't think of a second parent category, it might be a better idea to fold your smaller category into the parent.
== How to delete a category ==
Please refer to [[Wikipedia:Categories for discussion]]
== How to rename a category ==
Please refer to [[Wikipedia:Categories for discussion]]
==Organizing categories==
===Large categories===
When there are more than 200 entries in a category, only 200 are displayed on the screen and users have to click through multiple screens to see all the entries. To make it easy to navigate, add a TOC (table of contents). TOCs are added by typing:
:'''''{{tl|CategoryTOC}}''''' - which adds a complete TOC (Top, 0 - 9, A-Z)
:'''''{{tl|CatAZ}}''''' - which adds a TOC without numbers. This is for categories with members that only start with letters.
When a given category gets crowded, also consider making several subcategories. Group similar articles together in a meaningful and useful way that will make it easy for readers to navigate later. Remember that several subcategorization schemes can coexist (for example, if [[:Category:Software]] gets too big, you don't have to choose between subdividing it by function or subdividing it by platform, you can simultaneously subdivide it in both ways).
===Grouping categories===
A set of related categories often forms a hierarchy or a nexus. This can take several different forms, all of which are welcome and encouraged:
* A taxonomic grouping. For example, [[:Category:South Asian countries]] is part of a geographical hierarchy. [[:Category:Academic disciplines]] catalogs divisions between fields of study.
* A functional grouping. Examples: [[:Category:Ancient Rome]], [[:Category:World War II]], and [[:Category:Commercial item transport and distribution]]. These bring together articles and subcategories from different fields or taxonomies (history, war, culture, people, companies, industries, technologies) that have an interesting common thread.
* Hybrid forms. For example, [[:Category:Art]] is both part of the taxonomy of [[:Category:Academia]] and a cross-reference point for lots of things that have little in common except that they have something to do with art.
* Offshoot forms. For example, [[:Category:Film stubs]] contains subcategories of [[:Category:Comedy film stubs]] for [[comedy film]]s, and [[:Category:Drama film stubs]] for [[drama film]]s.
==Other requirements==
===Wikipedia namespace===
Categories relating to the [[Wikipedia:project namespace|Wikipedia namespace]] should be added only to the [[Wikipedia:talk page|talk page]] of articles. For example, tags suggesting the article [[:Category:To do|needs work]] would be placed on the talk page as they are relevant to editors and not an aid to browsing in the way ordinary categories are.
===User namespace===
Categories relating to the User namespace should be added only to Wikipedia-specific categories. Users should ''not'' add their user pages to article namespace categories such as [[:Category:People]] or other subcategories, [[:Category:Biologists]] etc, which are reserved for pages in the article namespace. However, it is appropriate to add a user page to ''Wikipedia-specific categories'' such as [[:Category:Wikipedians]] or other similar subcategories such as [[:Category:Wikipedian musicians]]. (See also [[m:Help:Category]] for guidelines on category "pollution").
If you copy an article to your user namespace (for example, as a temporary draft or in response to an [[Wikipedia:Edit war|edit war]]) you should decategorize it in one of the following ways, (where foobar is the category name):
#<nowiki>[[:Category:foobar]]</nowiki>, note the extra : before Category.
#<nowiki>{{cl|foobar}}</nowiki>, see {{tl|cl}}
#<nowiki>{{ccl|foobar}}</nowiki>, see {{tl|ccl}}
#<nowiki>{{lcs|foobar}}</nowiki>, see {{tl|lcs}}
===Image namespace===
See [[m:Help:Image_page#Categorizing_images|categorizing images]].
===Keep cats out of the sandbox===
Categories should not be put on articles that you are working on in the sandbox, nor on any page that you are using as a sandbox (such as an article draft that you are writing in a subpage of your userspace). In such cases you can add <tt><nowiki><nowiki></nowiki></tt> before the categories and <tt><nowiki></nowiki></nowiki></tt> following them, so that they will display without creating category listings. When the draft becomes an actual article you can remove the markup.
===Links to categories===
You can create a link to a category page without adding the page to that category by using a colon before the word Category. Example: <tt><nowiki>[[:Category:Automotive technologies]]</nowiki></tt> appears as [[:Category:Automotive technologies]].
===Redirected categories===
Although it is possible to attempt to redirect categories by adding a line such as <tt><nowiki>#REDIRECT [[:Category:Automotive technologies]]</nowiki></tt> to a category, it is not generally recommended because of limitations in the mediawiki software. Categories "redirected" in this way do not prevent the addition of articles to the redirected category. Articles added to the "redirected" category do not show up as in the target category.
Until these issues are addressed (in future versions of the software), '''#REDIRECT''' should not be added to category pages.
"Soft" redirects for categories can be created using {{[[Template:Category redirect|Category redirect]]}}. A [[Wikipedia:Bots|bot]] traverses categories redirected in this manner moving articles out of the redirected category into the target category, see [[Template talk:Category redirect]].
===Category sorting===
Contrary to some expectations, text after a pipe ("<tt>|</tt>") in a category link is not used in place of the category text. Rather, this text is used as the sort key on the category page itself. However, again contrary to expectations, that sort text is not displayed. One common application is to ignore "The" in article names, so <nowiki>[[Category:Rock and Roll Hall of Fame inductees|Beatles, The]]</nowiki> will make "The Beatles" list under B rather than T in the category.
As another example, the [[:Category:Three-digit Interstate Highways]] uses this property to sort secondary interstates by their primary. That is, the category link in the article for [[Interstate 190 (Illinois)]] is <tt><nowiki>[[Category:Three-digit Interstate Highways|90-1 Illinois]]</nowiki></tt>. This causes "Interstate 190 (Illinois)" to be listed right after "Interstate 189" and right before "Interstate 290 (Massachusetts)" under the heading "9" in the category page.
This feature is very useful for categories in which:
* the entries are people, in which case sorting by last name is preferable (example: [[:Category:Presidents of the United States]]).
* variations in the naming of entries causes inconsistent sorting (example: [[List of counties in Nebraska]], [[List of counties in Montana]], but [[List of Nevada counties]] in [[:Category:Lists of U.S. counties]]).
* the logical sort order is not alphabetical (example: individual month articles in year categories such as [[:Category:2004]], using e.g. the sort key "*2004-04" for April).
Using this method to sort category entries is sometimes informally referred to as ''the pipe trick''. However, this use of the pipe character is very different from the original Wikimedia [[m:Help:Piped link#Automatic conversion of the wikitext (pipe trick)|pipe trick]] which allows one to easily hide parenthetical disambiguation in links.
It is possible to force an article or subcategory to the top of the list by using a non-alphanumeric character as the first after the pipe. For example, using <tt><nowiki>[[Category:Ford| Ford Motor Company]]</nowiki></tt> (note the space) or <tt><nowiki>[[Category:Ford|*Ford Motor Company]]</nowiki></tt> would force that article to be displayed before all the others. Many editors feel that the space character produces the best aesthetic appearance when the category is displayed. Using a space or asterisk after the pipe is the customary way to categorize an article in a category with the same name, indicating that the article is the '''main topic article''' for that specific category. For an example, see [[:Category:Suspension bridges]]. Using {{tl|Catmore}} may be preferable - no consensus has been established yet. To list at the end (after z) of a category, the sort key ~ can be used <tt><nowiki>[[Category:Polyhedra|~Polyhedra templates]]</nowiki></tt>.
Other specifics:
*For more detailed guidelines about sorting names of people, see [[Wikipedia:Categorization of people#Ordering names in a category]].
*Don't start the category sort key with a lower case letter, unless you want to create a separate caption with that lower case letter in the category (note that the first lower case letter caption starts only after the last upper case letter caption)
*When trying to sort with ''numbers'' (e.g. [[wikipedia:Naming conventions (pieces of music)]]), don't forget to add an extra zero when more than 9 entries in the category are expected; and a second extra zero when more than 99, etc...: <s><nowiki>[[Category:Symphonies by Joseph Haydn|Symphony 13]]</nowiki></s> → <nowiki>[[Category:Symphonies by Joseph Haydn|Symphony 013]]</nowiki> (he wrote 108 symphonies). Categories sort by the first character, so leaving out the preceding zero would cause 10 to be sorted before 2.
*Ordinals often have to be converted to Arabic numerals: e.g. ''Pope John IX'': <nowiki>[[Category:Popes|John 09]]</nowiki> (+ zero added, there are XXIII popes with the name John)
*Don't forget to convert letters with diacritics, or non-standard letters to the nearest standard letters (that is: "standard" in English, at the time Wikipedia is written), examples:
**Diacritics are omitted: e.g. ''Étretat'': <nowiki>[[Category:Communes of Seine-Maritime|Etretat]]</nowiki>, or: ''Ål'': <nowiki>[[Category:Municipalities of Norway|Al]]</nowiki>
**Ligatures are separated: e.g. ''Æsir'': <nowiki>[[Category:Norse mythology|Aesir]]</nowiki>
**Sometimes which is appropriate depends on the language e.g.:
***From the [[Bruno K. Öijer]] article: <nowiki>[[Category:Living people|Oijer, Bruno K.]]</nowiki>. From the [[Ötzi the Iceman]] article:<nowiki>[[Category:Mummies|Oetzi the Iceman]]</nowiki> (in this case the German [[umlaut]] on the O is expanded to an "e" - preferably only omit the diacritic, without applying foreign rules that could make collation seem illogical in English: <nowiki>[[Category:Mummies|Otzi the Iceman]]</nowiki>.
***From the [[Arne Åhman]] article: <nowiki>[[Category:Swedish athletes|Ahman, Arne]]</nowiki>. From the [[Lasse Åberg]] article: <nowiki>[[Category:Swedish film directors|Aaberg, Lasse]]</nowiki> (Contrary to the previous example the "Å" is here expanded to "Aa" - again, better to only omit the diacritic, to avoid collation confusion ''in English'': <nowiki>[[Category:Swedish film directors|Aberg, Lasse]]</nowiki>.
===Year categories===
:''See also [[wikipedia:naming conventions (numbers and dates)#Articles on other standard time periods]]''
In categories which are years, such as [[:Category:2004]], special sorting guidelines apply:
* Entries should generally be sorted by ''topic'', so the article [[2004 in film]], for example, would contain the category reference <tt><nowiki>[[Category:2004|Film]]</nowiki></tt> while [[2004 Canadian budget]] would contain the reference <tt><nowiki>[[Category:2004|Canadian budget]]</nowiki></tt>; [[List of religious leaders in 2004]] would contain <tt><nowiki>[[Category:2004|Religious leaders]]</nowiki></tt>.
* The article about the year itself, [[2004]], should be sorted first among all articles by using <tt><nowiki>[[Category:2004|*]]</nowiki></tt>.
* Articles for individual months, such as [[October 2004]], should be sorted ''chronologically'' in the first section on the category page, in this case using <tt><nowiki>[[Category:2004|*2004-10]]</nowiki></tt>.
===Interlanguage links to categories===
Interlanguage links work just as they do for regular articles; <tt><nowiki>[[de:Kategorie:Mathematik]]</nowiki></tt> in [[:Category:Mathematics]] connects to the German counterpart. This can be a useful way to compare coverage, or to look for articles in need of interlanguage links. Note that the different languages may have adopted different standards and practices for categorization, so a given category might not exist in other languages.
==Tools==
* [[User:Pearle|Pearle]] can be used to automatically move articles from one category to another, get dumps of the category trees, and accomplish some other useful category-related tasks.
==Current projects==
See: [[Wikipedia:Categorization projects (current)]]
==Known category-related bugs==
Please report new category-related bugs on [http://bugzilla.wikimedia.org/ bugzilla] and list them below.
(Bugs higher than 1775 have not been checked)
===Redirects===
* <s>[[bugzilla:100|Redirects do not work properly with Categories]]</s> duplicate
* [[bugzilla:491|Categories need piping feature to list by alternative name]] (to show redirects next to the articles they redirect to in categories, when appropriate)
* <s>[[bugzilla:710|Redirect to category page doesn't work]]</s> fixed!
* [[bugzilla:927|Problem categorizing redirects]]
* <s>[[bugzilla:1333|Would like the ability to list an article under multiple names in its categories]]</s> duplicate
* <s>[[bugzilla:1476|Category tag on redirect pages does not work]]</s> fixed!
===Special:Categories===
* <s>[[bugzilla:146|Special:Categories:Add the number of articles in the category]]</s> fixed!
* [[bugzilla:461|Link to Special:Categories should be customisable]]
* [[bugzilla:844|Special:Categories should be paged by letter, like Special:Allpages]]
* <s>[[bugzilla:1064|Special:Categories don't display categories with no article]]</s> fixed!
===Large categories===
* [[bugzilla:1058|Dealing with large categories]]
* [[bugzilla:1212|On paged categories, article totals and subcat totals are incorrect]]
* [[bugzilla:1211|Subcategory paging is not separate from article paging]]
* [[bugzilla:1502|Table of contents for Categories]]
===Updating problems===
* <s>[[bugzilla:632|Slow deletion of members from categories]]</s>
* [[bugzilla:939|changes to links in a template do not update 'links', 'categorylinks', etc for pages including it]]
===General===
* <s>[[bugzilla:73|Images inappropriately added to categories]]</s> fixed
* <s>[[bugzilla:87|Category and interwiki tags produce ugly whitespace]]</s> fixed
* [[bugzilla:243|Add anchor tags to the headers used on category pages]]
* <s>[[bugzilla:144|Special:Recentchangeslinked for particular categories]]</s> fixed
* [[bugzilla:337|Characters in category names]]
* [[bugzilla:449|uncategorized pages report speedup hack]]
* [[bugzilla:450|Categories need to be structured by namespace]]
* <s>[[bugzilla:489|Categories link at bottom of article points to wrong place]]</s> duplicate
* <s>[[bugzilla:510|Feature request: Special random category page]]</s> fixed
* [[bugzilla:516|Ability to filter user contributions by time (e.g. "January 2003") or category]]
* <s>[[bugzilla:626|Different new page text for each namespace (enhancement)]] (the text you get for completely and partly empty category pages, category talk pages, etc.) </s> fixed
* <s>[[bugzilla:633|Pluralization in listing totals]]</s> fixed
* <s>[[bugzilla:706|syntax such that a (template) page can be un-categorized, but still categorise pages transcluding it]]</s> fixed
* <s>[[bugzilla:827|feature request: "newest changes" display for categories, "start from" ... input mask]]</s> duplicate
* [[bugzilla:835|syntax to transclude a page without the containing page inheriting categories, interlanguage links]]
* [[bugzilla:900|Category page listings have unbalanced columns]]
* [[bugzilla:931|automatic edit summary for categorizing pages]]
* [[bugzilla:943|RSS feed for category updates]]
* [[bugzilla:1029|Whitelist doesn't work correctly for categories]]
* [[bugzilla:1106|Feature request: boolean search in categories]]
* [[bugzilla:1119|Page move updates categories with sorting tweak]]
* <s>[[bugzilla:1169|Unstable categories (non-ASCII characters)]]</s> invalid
* <s>[[bugzilla:1239|New page created, db lag, result in double entries in categories]]</s> fixed
* <s>[[bugzilla:1242|Category list missing on edit page]]</s> fixed
* [[bugzilla:1289|Feature request: Category reverse sort by date]]
* <s>[[bugzilla:1467|Subpages don't work in Help_talk: and Category_talk:]]</s> fixed
* [[bugzilla:1701|Korean wikipedia's categories need new sectioning scheme]]
* [[bugzilla:1710|Ability to watch all articles in a category]]
* [[bugzilla:1745|can't edit the history versions of the categories!]]
* [[bugzilla:1775|Request: parameters in categories]]
* [[Wikipedia_talk:Categorization#Please_get_rid_of_.22no_subcategories.22.2C_and_.5B.2B.5D_when_it_has_no_subcategories|"No subcategories" display - I consider it a bug, not submitted.]]
==When to use categories==
Categories (along with other features like cross-references, lists, and infoboxes) help users find information, even if they don't know that it exists or what it's called.
Every page in the article namespace should belong to at least one category. Categories should be major topics that are likely to be useful to someone reading the article.
:'''Article:''' [[Michael Jackson]]
:'''Useful category:''' [[:Category:Pop singers]]
:'''Not useful:''' ''Category:Musicians whose first name starts with M''
Questions to ask to determine whether it is appropriate to add an article to a category:
*If the category does not already exist, is it possible to write a few paragraphs or more on the subject of the category, explaining it?
*If you go to the article from the category, will it be obvious why the article was put in the category? Is the category subject prominently discussed in the article?
If the answer to either of these questions is no, then the category is probably inappropriate. Note that it is always appropriate to add articles to categories that fit into well established taxonomies. For example, every article about a musical album is categorized in some <nowiki>[[Category:Artistname albums]]</nowiki> category, which is in turn categorized in [[:Category:Albums by artist]].
==Guidelines==
{{Meta}}
===Some general guidelines===
#Categories are mainly used to browse through similar articles. Make decisions about the structure of categories and subcategories that make it easy for users to browse through similar articles.
#An article will often be in several categories. Restraint should be used as categories become less effective the more there are on any given article.
#Articles should not usually be in both a category and its subcategory. For example [[Golden Gate Bridge]] is in [[:Category:Suspension bridges]], so it should not also be in [[:Category:Bridges]]. However there are occasions when this guideline can and should be ignored. For example, [[Robert Duvall]] is in [[:Category:Film actors]] as well as its subcategory [[:Category:Best Actor Academy Award winners]]. See #5 for another exception. For more about this see '''[[Wikipedia:Categorization/Categories and subcategories]]'''
#Check to see where siblings of the article reside. If there are few if any articles in a category, the article probably belongs in one of the subcategories.
#Articles should be placed in categories with the same name. However, the article and the category do not have to be categorized the same way. The article can also be placed in categories populated with similar articles. The category can be put into categories populated with similar subcategories. For an example of this see [[George W. Bush]] and [[:Category:George W. Bush]].
#There are often occasions when articles might ideally be moved from a category to two or more of its subcategories, but not all of the subcategories exist. In such cases consider creating the additional subcategories, but if you decide not to do so, leave the articles in the parent category for the time being.
#Bend the rules above when it makes sense, but only if no other solution can be found.
#Categories appear without annotations, so be careful of [[NPOV]] when creating or filling categories. Unless it is self-evident and uncontroversial that something belongs in a category, it should not be put into a category. A list might be a better option.
#If you don't know where to put an article don't worry about it. Instead of adding a category, use the {{tl|uncategorized}} tag to bring attention to the article. Editors who love to categorize articles will find a good home for your article.
===Categories vs. Lists vs. Info boxes===
For alternative methods of grouping articles, and the circumstances in which they should be used, see [[Wikipedia:Categories, lists, and series boxes]].
===Categories applied to articles on people===
A separate wikipedia page [[Wikipedia:Categorization of people]] was created to help you in designing, applying and checking categories that are used for articles on people.
===Categories do not form a tree===
Each Wikipedia article can appear in more than one category, and each category can appear in more than one parent category. Multiple categorization schemes co-exist simultaneously. In other words, categories do not form a strict hierarchy or [[tree structure]], but a more general [[directed acyclic graph]] (or close to it; see below).
Nevertheless, parts of the category graph will be tree-like, and it may be convenient to think of parts of the category graph as being like multiple overlapping trees. When applying the guidelines above, consider each tree to be independent of the overlapping trees. A person browsing through a hierarchy should find every article that belongs in that hierarchy. This can lead to a good deal of debate as to what the hierarchies actually are. To clarify the structure of the hierarchy and help people browse through it, you can add a classification to each category. For more about this, see [[Wikipedia:Classification]].
===Cycles should usually be avoided===
Although the MediaWiki software does not prevent [[cycle (graph theory)|cycles]] (loops), these usually should be avoided. Cycles can be confusing to some readers, they can challenge some automated searching processes and they can grow quite large. For example, in January 2006 a 22-member category cycle was discovered and eliminated.
However, acceptable loops also exist. Self-referencing systems such as the [[meta-]] fields naturally create cycles that provide many examples. This type of cycle involves making a category one of its own subcategories. A real-world example of a self-referencing system is “education about education,” such as:
:Classification: [[:category:Education|Education]]: [[:category:Social sciences|Social sciences]]: [[:category:Academic disciplines|Academic disciplines]]: [[:category:Academia|Academia]]: [[:category:Education|Education]]: ...
Another type of cycle involves making two categories subcategories of each other. Loops such as these can be avoided by linking the categories manually to each other by adding "See also:[[:Category:Foo]]" to each category page. For an example of this see [[:Category:World Trade Center]] and [[:Category:September 11, 2001 attacks]].
==How to put an article into categories==
{{Style}}
Adding an article to a category is as simple as editing the article and adding a link to the category. For instance, to add ''[[Felis silvestris catus]]'' article to the "fluffy creatures" category, you would edit the article and enter <tt><nowiki>[[Category:Fluffy creatures]]</nowiki></tt> at the bottom, but ''before'' [[Wikipedia:Interlanguage links|interlanguage links]]. The appeal of categories is that unlike lists, they update themselves automatically, and you don't have to edit the category to add an article to it. However, categories are not a substitute for [[Wikipedia:list|list]]s, and you will find that many articles belong to both lists and categories.
When adding an article to a category, or creating categories, one should be careful to use the correct categories and subcategories. Horizontal categorization, directly below, refers to placing an article in the correct category while vertical categorization refers to placing an article in the correct ''sub''category.
When assigning an article into categories, try to be thorough in a
"horizontal" sense. The topic may be associated with a geographic
area, a historical period, an academic subfield, a certain type of
thing (like a food or an ornament), and/or a special interest topic
(like [[:Category:Roman Empire|Roman Empire]] or [[:Category:LGBT|LGBT]]). You might need to poke around the
category hierarchy a bit to find the right place. Try searching for
articles similar to the article you are categorizing to get ideas or
to find the most appropriate place.
In the "vertical" dimension, Wikipedia has traditionally been more frugal, placing articles only in the most specific categories they reasonably fit in. Thus, if there is a [[:Category:American film actors]], [[John Wayne]] would go there and not in [[:Category:Film actors]] or [[:Category:American actors]]. However, there is a school of thought that argues that, because different users may be interested in different categories, and because placing articles in multiple categories takes up minimal additional space, in some cases one should place articles in all the categories that apply.
<!-- For example, [[Elizabeth_II_of_the_United_Kingdom|Queen Elizabeth]] should not be listed directly under People, but 'Category:Monarchs of the United Kingdom' might be a good place for her. We know that all Queens of the United Kingdom qualify as Famous Britons and as Royalty, and all of those folks qualify as People. Sometimes there's a good reason to assign an article to two categories, one of which is a direct or indirect subcategory of another. For a well-argued case study, see [[John Lennon]]. -->
For more about this see '''[[Wikipedia:Categorization/Categories and subcategories]]'''
==How to create categories==
Creating a category is as simple as adding a link to a category that doesn't yet exist. For instance, to create the "fluffy creatures" category, you would edit an article and enter <tt><nowiki>[[Category:Fluffy creatures]]</nowiki></tt> the same way as adding it to any other category. The <tt>Category:Fluffy creatures</tt> will automatically be created when the edit is saved.
===Category naming===
Categories follow the same general naming conventions as articles, for example do not capitalize regular nouns. For specific conventions related to categories, see [[Wikipedia:Naming conventions (categories)]].
Whatever categories you add, make sure they do not implicitly violate
the [[WP:NPOV|neutral point of view policy]]. If the nature of something is in dispute (like whether or not it's fictional or scientific or whatever),
you may want to avoid labelling it or mark the categorization as
disputed. Most categorizations are pretty straightforward, though.
===Look before you leap===
Before creating a category, look to see if one already exists. The best way to do this is to first add the category to your article but preview before saving. If the category appears in blue at the bottom of the page, the category already exists. If it is in red, then you will be creating a new category. Check the capitalization of the category name. For any red categories, you should look for categories with similar names before creating a new category. One way to do this is to think of the parent category for the new category. Search for it and then look at the subcategories in the parent. You may find that a category already exists that is similar to the one you are thinking about creating.
You may see some inconsistencies when first creating the category: it may alternate between appearing empty and appearing with your first additions. It will probably correct itself in a few minutes. Note that, although "uncreated" categories ''will'' correctly list articles that have been assigned to them, the category page itself does not exist until it is manually created. The easiest way to create the category page is to follow the red category link from your article and create a new category page with a parent category and a category description as explained in the next section.
==How to create subcategories==
Create subcategory pages by putting the name of the parent category on a category page that you would like to be the subcategory. Child categories (subcategories) are created by putting <nowiki>[[Category:</nowiki>''parent_category_name''<nowiki>]]</nowiki> '''on the lower-level category pages'''. For example, on a (sub)category page called ''category:Roses'' you put <nowiki>[[Category:Flowers]]</nowiki>, Roses becomes a subcategory of Flowers.
When writing the description for a category try to give it at least two parent categories. For example, [[:Category:British writers]] should be in both [[:Category:Writers by nationality]] and [[:Category:British people]]. A few categories do only merely subdivide their parent category, but unless the parent category has many potential articles under it, or many potential subdivisions, if you can't think of a second parent category, it might be a better idea to fold your smaller category into the parent.
== How to delete a category ==
Please refer to [[Wikipedia:Categories for discussion]]
== How to rename a category ==
Please refer to [[Wikipedia:Categories for discussion]]
==Organizing categories==
===Large categories===
When there are more than 200 entries in a category, only 200 are displayed on the screen and users have to click through multiple screens to see all the entries. To make it easy to navigate, add a TOC (table of contents). TOCs are added by typing:
:'''''{{tl|CategoryTOC}}''''' - which adds a complete TOC (Top, 0 - 9, A-Z)
:'''''{{tl|CatAZ}}''''' - which adds a TOC without numbers. This is for categories with members that only start with letters.
When a given category gets crowded, also consider making several subcategories. Group similar articles together in a meaningful and useful way that will make it easy for readers to navigate later. Remember that several subcategorization schemes can coexist (for example, if [[:Category:Software]] gets too big, you don't have to choose between subdividing it by function or subdividing it by platform, you can simultaneously subdivide it in both ways).
===Grouping categories===
A set of related categories often forms a hierarchy or a nexus. This can take several different forms, all of which are welcome and encouraged:
* A taxonomic grouping. For example, [[:Category:South Asian countries]] is part of a geographical hierarchy. [[:Category:Academic disciplines]] catalogs divisions between fields of study.
* A functional grouping. Examples: [[:Category:Ancient Rome]], [[:Category:World War II]], and [[:Category:Commercial item transport and distribution]]. These bring together articles and subcategories from different fields or taxonomies (history, war, culture, people, companies, industries, technologies) that have an interesting common thread.
* Hybrid forms. For example, [[:Category:Art]] is both part of the taxonomy of [[:Category:Academia]] and a cross-reference point for lots of things that have little in common except that they have something to do with art.
* Offshoot forms. For example, [[:Category:Film stubs]] contains subcategories of [[:Category:Comedy film stubs]] for [[comedy film]]s, and [[:Category:Drama film stubs]] for [[drama film]]s.
==Other requirements==
===Wikipedia namespace===
Categories relating to the [[Wikipedia:project namespace|Wikipedia namespace]] should be added only to the [[Wikipedia:talk page|talk page]] of articles. For example, tags suggesting the article [[:Category:To do|needs work]] would be placed on the talk page as they are relevant to editors and not an aid to browsing in the way ordinary categories are.
===User namespace===
Categories relating to the User namespace should be added only to Wikipedia-specific categories. Users should ''not'' add their user pages to article namespace categories such as [[:Category:People]] or other subcategories, [[:Category:Biologists]] etc, which are reserved for pages in the article namespace. However, it is appropriate to add a user page to ''Wikipedia-specific categories'' such as [[:Category:Wikipedians]] or other similar subcategories such as [[:Category:Wikipedian musicians]]. (See also [[m:Help:Category]] for guidelines on category "pollution").
If you copy an article to your user namespace (for example, as a temporary draft or in response to an [[Wikipedia:Edit war|edit war]]) you should decategorize it in one of the following ways, (where foobar is the category name):
#<nowiki>[[:Category:foobar]]</nowiki>, note the extra : before Category.
#<nowiki>{{cl|foobar}}</nowiki>, see {{tl|cl}}
#<nowiki>{{ccl|foobar}}</nowiki>, see {{tl|ccl}}
#<nowiki>{{lcs|foobar}}</nowiki>, see {{tl|lcs}}
===Image namespace===
See [[m:Help:Image_page#Categorizing_images|categorizing images]].
===Keep cats out of the sandbox===
Categories should not be put on articles that you are working on in the sandbox, nor on any page that you are using as a sandbox (such as an article draft that you are writing in a subpage of your userspace). In such cases you can add <tt><nowiki><nowiki></nowiki></tt> before the categories and <tt><nowiki></nowiki></nowiki></tt> following them, so that they will display without creating category listings. When the draft becomes an actual article you can remove the markup.
===Links to categories===
You can create a link to a category page without adding the page to that category by using a colon before the word Category. Example: <tt><nowiki>[[:Category:Automotive technologies]]</nowiki></tt> appears as [[:Category:Automotive technologies]].
===Redirected categories===
Although it is possible to attempt to redirect categories by adding a line such as <tt><nowiki>#REDIRECT [[:Category:Automotive technologies]]</nowiki></tt> to a category, it is not generally recommended because of limitations in the mediawiki software. Categories "redirected" in this way do not prevent the addition of articles to the redirected category. Articles added to the "redirected" category do not show up as in the target category.
Until these issues are addressed (in future versions of the software), '''#REDIRECT''' should not be added to category pages.
"Soft" redirects for categories can be created using {{[[Template:Category redirect|Category redirect]]}}. A [[Wikipedia:Bots|bot]] traverses categories redirected in this manner moving articles out of the redirected category into the target category, see [[Template talk:Category redirect]].
===Category sorting===
Contrary to some expectations, text after a pipe ("<tt>|</tt>") in a category link is not used in place of the category text. Rather, this text is used as the sort key on the category page itself. However, again contrary to expectations, that sort text is not displayed. One common application is to ignore "The" in article names, so <nowiki>[[Category:Rock and Roll Hall of Fame inductees|Beatles, The]]</nowiki> will make "The Beatles" list under B rather than T in the category.
As another example, the [[:Category:Three-digit Interstate Highways]] uses this property to sort secondary interstates by their primary. That is, the category link in the article for [[Interstate 190 (Illinois)]] is <tt><nowiki>[[Category:Three-digit Interstate Highways|90-1 Illinois]]</nowiki></tt>. This causes "Interstate 190 (Illinois)" to be listed right after "Interstate 189" and right before "Interstate 290 (Massachusetts)" under the heading "9" in the category page.
This feature is very useful for categories in which:
* the entries are people, in which case sorting by last name is preferable (example: [[:Category:Presidents of the United States]]).
* variations in the naming of entries causes inconsistent sorting (example: [[List of counties in Nebraska]], [[List of counties in Montana]], but [[List of Nevada counties]] in [[:Category:Lists of U.S. counties]]).
* the logical sort order is not alphabetical (example: individual month articles in year categories such as [[:Category:2004]], using e.g. the sort key "*2004-04" for April).
Using this method to sort category entries is sometimes informally referred to as ''the pipe trick''. However, this use of the pipe character is very different from the original Wikimedia [[m:Help:Piped link#Automatic conversion of the wikitext (pipe trick)|pipe trick]] which allows one to easily hide parenthetical disambiguation in links.
It is possible to force an article or subcategory to the top of the list by using a non-alphanumeric character as the first after the pipe. For example, using <tt><nowiki>[[Category:Ford| Ford Motor Company]]</nowiki></tt> (note the space) or <tt><nowiki>[[Category:Ford|*Ford Motor Company]]</nowiki></tt> would force that article to be displayed before all the others. Many editors feel that the space character produces the best aesthetic appearance when the category is displayed. Using a space or asterisk after the pipe is the customary way to categorize an article in a category with the same name, indicating that the article is the '''main topic article''' for that specific category. For an example, see [[:Category:Suspension bridges]]. Using {{tl|Catmore}} may be preferable - no consensus has been established yet. To list at the end (after z) of a category, the sort key ~ can be used <tt><nowiki>[[Category:Polyhedra|~Polyhedra templates]]</nowiki></tt>.
Other specifics:
*For more detailed guidelines about sorting names of people, see [[Wikipedia:Categorization of people#Ordering names in a category]].
*Don't start the category sort key with a lower case letter, unless you want to create a separate caption with that lower case letter in the category (note that the first lower case letter caption starts only after the last upper case letter caption)
*When trying to sort with ''numbers'' (e.g. [[wikipedia:Naming conventions (pieces of music)]]), don't forget to add an extra zero when more than 9 entries in the category are expected; and a second extra zero when more than 99, etc...: <s><nowiki>[[Category:Symphonies by Joseph Haydn|Symphony 13]]</nowiki></s> → <nowiki>[[Category:Symphonies by Joseph Haydn|Symphony 013]]</nowiki> (he wrote 108 symphonies). Categories sort by the first character, so leaving out the preceding zero would cause 10 to be sorted before 2.
*Ordinals often have to be converted to Arabic numerals: e.g. ''Pope John IX'': <nowiki>[[Category:Popes|John 09]]</nowiki> (+ zero added, there are XXIII popes with the name John)
*Don't forget to convert letters with diacritics, or non-standard letters to the nearest standard letters (that is: "standard" in English, at the time Wikipedia is written), examples:
**Diacritics are omitted: e.g. ''Étretat'': <nowiki>[[Category:Communes of Seine-Maritime|Etretat]]</nowiki>, or: ''Ål'': <nowiki>[[Category:Municipalities of Norway|Al]]</nowiki>
**Ligatures are separated: e.g. ''Æsir'': <nowiki>[[Category:Norse mythology|Aesir]]</nowiki>
**Sometimes which is appropriate depends on the language e.g.:
***From the [[Bruno K. Öijer]] article: <nowiki>[[Category:Living people|Oijer, Bruno K.]]</nowiki>. From the [[Ötzi the Iceman]] article:<nowiki>[[Category:Mummies|Oetzi the Iceman]]</nowiki> (in this case the German [[umlaut]] on the O is expanded to an "e" - preferably only omit the diacritic, without applying foreign rules that could make collation seem illogical in English: <nowiki>[[Category:Mummies|Otzi the Iceman]]</nowiki>.
***From the [[Arne Åhman]] article: <nowiki>[[Category:Swedish athletes|Ahman, Arne]]</nowiki>. From the [[Lasse Åberg]] article: <nowiki>[[Category:Swedish film directors|Aaberg, Lasse]]</nowiki> (Contrary to the previous example the "Å" is here expanded to "Aa" - again, better to only omit the diacritic, to avoid collation confusion ''in English'': <nowiki>[[Category:Swedish film directors|Aberg, Lasse]]</nowiki>.
===Year categories===
:''See also [[wikipedia:naming conventions (numbers and dates)#Articles on other standard time periods]]''
In categories which are years, such as [[:Category:2004]], special sorting guidelines apply:
* Entries should generally be sorted by ''topic'', so the article [[2004 in film]], for example, would contain the category reference <tt><nowiki>[[Category:2004|Film]]</nowiki></tt> while [[2004 Canadian budget]] would contain the reference <tt><nowiki>[[Category:2004|Canadian budget]]</nowiki></tt>; [[List of religious leaders in 2004]] would contain <tt><nowiki>[[Category:2004|Religious leaders]]</nowiki></tt>.
* The article about the year itself, [[2004]], should be sorted first among all articles by using <tt><nowiki>[[Category:2004|*]]</nowiki></tt>.
* Articles for individual months, such as [[October 2004]], should be sorted ''chronologically'' in the first section on the category page, in this case using <tt><nowiki>[[Category:2004|*2004-10]]</nowiki></tt>.
===Interlanguage links to categories===
Interlanguage links work just as they do for regular articles; <tt><nowiki>[[de:Kategorie:Mathematik]]</nowiki></tt> in [[:Category:Mathematics]] connects to the German counterpart. This can be a useful way to compare coverage, or to look for articles in need of interlanguage links. Note that the different languages may have adopted different standards and practices for categorization, so a given category might not exist in other languages.
==Tools==
* [[User:Pearle|Pearle]] can be used to automatically move articles from one category to another, get dumps of the category trees, and accomplish some other useful category-related tasks.
==Current projects==
See: [[Wikipedia:Categorization projects (current)]]
==Known category-related bugs==
Please report new category-related bugs on [http://bugzilla.wikimedia.org/ bugzilla] and list them below.
(Bugs higher than 1775 have not been checked)
===Redirects===
* <s>[[bugzilla:100|Redirects do not work properly with Categories]]</s> duplicate
* [[bugzilla:491|Categories need piping feature to list by alternative name]] (to show redirects next to the articles they redirect to in categories, when appropriate)
* <s>[[bugzilla:710|Redirect to category page doesn't work]]</s> fixed!
* [[bugzilla:927|Problem categorizing redirects]]
* <s>[[bugzilla:1333|Would like the ability to list an article under multiple names in its categories]]</s> duplicate
* <s>[[bugzilla:1476|Category tag on redirect pages does not work]]</s> fixed!
===Special:Categories===
* <s>[[bugzilla:146|Special:Categories:Add the number of articles in the category]]</s> fixed!
* [[bugzilla:461|Link to Special:Categories should be customisable]]
* [[bugzilla:844|Special:Categories should be paged by letter, like Special:Allpages]]
* <s>[[bugzilla:1064|Special:Categories don't display categories with no article]]</s> fixed!
===Large categories===
* [[bugzilla:1058|Dealing with large categories]]
* [[bugzilla:1212|On paged categories, article totals and subcat totals are incorrect]]
* [[bugzilla:1211|Subcategory paging is not separate from article paging]]
* [[bugzilla:1502|Table of contents for Categories]]
===Updating problems===
* <s>[[bugzilla:632|Slow deletion of members from categories]]</s>
* [[bugzilla:939|changes to links in a template do not update 'links', 'categorylinks', etc for pages including it]]
===General===
* <s>[[bugzilla:73|Images inappropriately added to categories]]</s> fixed
* <s>[[bugzilla:87|Category and interwiki tags produce ugly whitespace]]</s> fixed
* [[bugzilla:243|Add anchor tags to the headers used on category pages]]
* <s>[[bugzilla:144|Special:Recentchangeslinked for particular categories]]</s> fixed
* [[bugzilla:337|Characters in category names]]
* [[bugzilla:449|uncategorized pages report speedup hack]]
* [[bugzilla:450|Categories need to be structured by namespace]]
* <s>[[bugzilla:489|Categories link at bottom of article points to wrong place]]</s> duplicate
* <s>[[bugzilla:510|Feature request: Special random category page]]</s> fixed
* [[bugzilla:516|Ability to filter user contributions by time (e.g. "January 2003") or category]]
* <s>[[bugzilla:626|Different new page text for each namespace (enhancement)]] (the text you get for completely and partly empty category pages, category talk pages, etc.) </s> fixed
* <s>[[bugzilla:633|Pluralization in listing totals]]</s> fixed
* <s>[[bugzilla:706|syntax such that a (template) page can be un-categorized, but still categorise pages transcluding it]]</s> fixed
* <s>[[bugzilla:827|feature request: "newest changes" display for categories, "start from" ... input mask]]</s> duplicate
* [[bugzilla:835|syntax to transclude a page without the containing page inheriting categories, interlanguage links]]
* [[bugzilla:900|Category page listings have unbalanced columns]]
* [[bugzilla:931|automatic edit summary for categorizing pages]]
* [[bugzilla:943|RSS feed for category updates]]
* [[bugzilla:1029|Whitelist doesn't work correctly for categories]]
* [[bugzilla:1106|Feature request: boolean search in categories]]
* [[bugzilla:1119|Page move updates categories with sorting tweak]]
* <s>[[bugzilla:1169|Unstable categories (non-ASCII characters)]]</s> invalid
* <s>[[bugzilla:1239|New page created, db lag, result in double entries in categories]]</s> fixed
* <s>[[bugzilla:1242|Category list missing on edit page]]</s> fixed
* [[bugzilla:1289|Feature request: Category reverse sort by date]]
* <s>[[bugzilla:1467|Subpages don't work in Help_talk: and Category_talk:]]</s> fixed
* [[bugzilla:1701|Korean wikipedia's categories need new sectioning scheme]]
* [[bugzilla:1710|Ability to watch all articles in a category]]
* [[bugzilla:1745|can't edit the history versions of the categories!]]
* [[bugzilla:1775|Request: parameters in categories]]
* [[Wikipedia_talk:Categorization#Please_get_rid_of_.22no_subcategories.22.2C_and_.5B.2B.5D_when_it_has_no_subcategories|"No subcategories" display - I consider it a bug, not submitted.]]
