Wikipedia:Categories, lists, and navigation templates
Wikipedia offers several ways to group articles: categories, list articles (including item lists, as well as topical glossary, index, outline, and timeline articles), other lists including embedded lists, and navigation templates (of which article series boxes are one type). The grouping of articles by one method neither requires nor forbids the use of the other methods for the same informational grouping. Instead, each method of organizing information has its own advantages and disadvantages, and is applied for the most part independently of the other methods following the guidelines and standards that have evolved on Wikipedia for each of these systems.
Accordingly, these methods should not be considered in conflict with each other. Rather, they are synergistic, each one complementing the others. For example, since editors differ in style, some favor building lists while others favor building categories, allowing links to be gathered in two different ways, with lists often leapfrogging categories, and vice versa. This approach has resulted in two main link-based systems of navigating Wikipedia. See the navigation menu at the top of Wikipedia:Contents, and see Category:Wikipedia categories. Many users prefer to browse Wikipedia through its lists, while others prefer to navigate by category; and lists are more obvious to beginners, who may not discover the category system right away. Therefore, the "category camp" should not delete or dismantle Wikipedia's lists, and the "list camp" shouldn't tear down Wikipedia's category system—doing so wastes valuable resources. Instead, each should be used to update the other.
At the same time, there may be circumstances where consensus determines that one or more methods of presenting information is inappropriate for Wikipedia. For instance, the guideline on overcategorization sets out a number of situations in which consensus has consistently determined that categories should not be used. A regularly occurring outcome at WP:CFD for some deleted categories is to listify, because there are cases where lists are appropriate while categories may not be (e.g. List of unusual units of measurement exists as a list, but not as a category Category:Unusual units of measurement).
Category workers, list builders and outline builders, and series box designers all endeavor to develop comprehensive networks of links for navigating the encyclopedia. Because of this, increasingly, multiple entries to fields of knowledge are being provided. Take "symphonies", for example:
- Categories: Category:Symphonies
- Lists: List of symphonies with names
- Navigation Templates: Template:Symphonies by number and name
It is neither improper nor uncommon to simultaneously have a category, a list, and a navigation template that all cover the same topic. These systems of organizing information are considered to be complementary, not inappropriately duplicative. Furthermore, arguing that a category duplicates a list (or vice versa) at a deletion discussion is not a valid reason for deletion and should be avoided. Redirects of list articles to categories are highly discouraged: list articles should take the place of the redirect.
Consider that lists may include features not available to categories, and building a rudimentary list of links is a useful step in improving a list. Deleting these rudimentary lists is a waste of these building blocks, and unnecessarily pressures list builders into providing a larger initial commitment of effort whenever they wish to create a new list, which may be felt as a disincentive. When deciding whether to create or avoid a list, the existence of a category on the same topic is irrelevant.
Below is a comparison of how these techniques group information and the advantages and disadvantages of each.
Categories
Compared to a list, a category may have both advantages and disadvantages.
Example of a category page. Every page in the article namespace should have at least one category. Categories should be on major topics that are likely to be useful to someone reading the article.
- Article: Michael Jackson
- Useful category: Category:American pop singers
- Not useful: Category:Musicians whose first name starts with M
A category is probably inappropriate if the answer to the following questions is "no":
- Is it possible to write a few paragraphs or more on the subject of a category, explaining it?
- If you go to the article from the category, will it be obvious why it's there? Is the category subject prominently discussed in the article?
An article will often be in several categories. Restraint should be used, however—categories become less effective the more there are on a given article.
An article should usually not be in both a category and its subcategory, e.g. Microsoft Office is in Category:Microsoft software, so should not also be in Category:Software—except when the article defines a category as well as being in a higher category, e.g. Ohio is in both Category:States of the United States and Category:Ohio (a good way to understand this exception is that if an article exists, and then a category is created on the same subject as the article, it should not cause the article to be removed from any of its categories).
Exceptions should also be considered when the article subject has a relevance to the parent category that is not expressed by the subcategory's definition. For instance, if Category:People executed by guillotine during the French Revolution was the only subcategory of Category:People of the French Revolution, it would not make sense to remove major figures of the French Revolution solely because of the means of their death.
Categories appear without annotations, so be careful of neutral point of view (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. Especially see Wikipedia:Categorization of people.
An exception to the above rules is Category:Wikipedia maintenance, which contains categories intended to be temporary.
Every category should be a subcategory of some other category. You can start from the top of the articles category hierarchy at Category:Main topic classifications. If you think a good parent probably exists but you just can't find it, add the {{Uncategorized}} tag. Your category will show up at Special:Uncategorizedcategories.
Categories have sort keys like other pages, although they are used in a more flexible fashion. See WP:SORTKEY for technical considerations.
For articles without any stable category, the {{Uncategorized}} tag can be used to bring attention to it, either on its own, or in the format {{uncat|April2024}}. There is also an automatically updated list at Special:Uncategorizedpages which displays uncategorized/stubbed articles; however it only updates once every few days, and only lists 1000 articles at a time. So it is always best to explicitly place an {{uncat}} tag, if you are uncertain how an article should be categorized.
Advantages of a category
- Auto-linking. Create a link to a category on an article page, and a corresponding link to that article will be visible on the category page.
- Multi-directional navigation. A category can contain multiple subcategories, and can also be part of several categories. Categories are organized within Wikipedia into a web of knowledge starting with Category:Wikipedia categories.
- Good for exploratory browsing of Wikipedia.
- Less susceptible to external linkspam than other types of pages, because only Wikipedia articles can be members of categories.
- Relatively unobtrusive in that they generally don't distract from the flow of the article.
- Search can use the incategory parameter to exclude or include all pages in that category. Subcategories are not included, but multiple terms can be added.
Disadvantages of a category
- Can't be edited directly to add or remove entries. This must be done at the bottom of each article to be included or excluded from the category.
- Categories only list the name of a page. And 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 verify a topic meets a category's criteria of inclusion.
- Entries are arranged in alphabetical order only (though you can control the alphabetization). They cannot be organized into sections and subsections on a single page, each with its own descriptive introduction.
- Can be difficult to maintain:
- A category with hundreds of items cannot be moved except by editing hundreds of articles (though a bot can help)
- Tracking changes to a category is difficult because a category's edit history does not show when entries were added or removed from the category. So there is no easy way to tell when an article is removed from a category—it simply disappears with no indication that it was ever there in the first place. Wikipedia's watchlist feature does enable a user to watch a category for category membership changes.
- Does not support other forms of tracking, such as adding red links. (Red links are useful as gap indicators and as task reminders to create those articles.) However stubs can be added to categories.
- Alternative names for the same item can be included only by including redirects in the category.
- It is not obvious to new users that categories exist, how to add items to them, how to link new categories into existing schemes, nor how to deal with point of view (POV) concerns.
- Categories are not shown in mobile view.
- Display of items in a category is limited to 200 on a page. To see the full contents of a category with more members than this, multiple pages need to be viewed.
Lists
Compared to a category, a list may have both advantages and disadvantages.
Example of a list: List of dog breeds