Help:Categories

Categories group related pages so readers and editors can navigate topics efficiently. This help page explains how to add categories to pages, create new categories correctly, and maintain category structures.

What are categories?

Categories are navigational aids placed at the end of pages. They collect pages sharing a theme into browsable lists.

Example: An article on Prague might belong to , , and .

Adding a page to a category

Place a category link anywhere in the wikitext (normally at the bottom):

Basic: [[Category:Cities in the Czech Republic]]
With sort key: [[Category:Cities in the Czech Republic|Prague]] (forces sorting under “P” instead of “P” with diacritics or starting article)
Default sort key (for all categories on the page): {{DEFAULTSORT:Prague}}

Tips:

Use existing categories where possible; check parent categories to find the best fit.
Avoid over-categorization; prefer the most specific applicable categories.
Do not add hidden maintenance categories to reader-facing content unless needed.

Viewing and navigating categories

At the bottom of any categorized page, category links appear. Clicking one shows:

Subcategories (if any)
Pages in the category
Navigation up to parent categories

You can also search for categories via:

Special pages: Special:Categories, Special:Search
Category trees: Special:CategoryTree

Creating a new category

Only create categories when they meet project guidelines and have enough potential members.

Steps: 1. Decide the category name using common naming conventions (plural nouns, clear scope). 2. Create the category page: go to Category:Your name and click “Create”. 3. Add a brief description and parent categories:

  * Example:
    
     This category contains cities located in the Czech Republic.
     [[Category:Populated places in the Czech Republic]]
     [[Category:Cities by country]]

4. Optionally add a {{Cat main}} or {{See also}} pointing to a related list or overview article. 5. Populate the category with a reasonable number of pages (generally >3 to justify existence).

Parent categories and subcategories

Build clear hierarchies:

A category should be placed within one or more logical parents.
Use subcategories to avoid long flat lists; for example:

 * 
   * 
   *

Avoid cycles:

A category must not be a parent of itself, directly or indirectly.
Do not list a page in both a parent and subcategory unless policy allows.

Sort keys

Sorting determines how pages appear in a category list:

Per-category: [[Category:Czech painters|Mucha, Alphonse]]
Global default: {{DEFAULTSORT:Mucha, Alphonse}}
Diacritics: Use ASCII-friendly sort keys to improve ordering (e.g., {{DEFAULTSORT:Ceska Republika}} for “Česká republika”).

Hidden categories

Hidden categories do not display to readers, but are visible to editors via page footer or preferences.

Mark a category hidden by adding: __HIDDENCAT__ on the category page.
Common uses: maintenance, tracking, cleanup tasks.
Do not hide topical categories intended for readers.

Maintenance categories

Maintenance categories help track issues (e.g., pages needing citations).

Add via templates (e.g., {{Refimprove}}) rather than manual category links when possible.
Keep scopes focused and avoid duplication.

Category descriptions

Category pages should explain:

Scope: what belongs and what does not.
Naming rationale if non-obvious.
Relevant links: parent categories, related lists, and portals.

Example description: This category contains articles about municipalities in the South Moravian Region. [[Category:Municipalities in the Czech Republic]] [[Category:South Moravian Region]]

Deletion and renaming

Propose deletion via standard discussion processes (e.g., Categories for discussion).
Renaming/moving categories typically requires bot-assisted recategorization; consult project guidelines.
Avoid mass moves without consensus; document changes for editors.

Good practices

Prefer specific categories over broad ones when both apply.
Keep category trees balanced; avoid overly deep or overly flat structures.
Check existing conventions in relevant WikiProjects before creating or altering categories.
Use {{DEFAULTSORT}} consistently for names with diacritics or articles (“The”, “A”, etc.).

Examples

Add multiple categories with default sort

{{DEFAULTSORT:Prague}} [[Category:Capitals in Europe]] [[Category:Cities in the Czech Republic]] [[Category:Tourism in the Czech Republic]]

New category with parent links and hidden flag (maintenance)

__HIDDENCAT__ Pages needing Czech IPA cleanup. [[Category:Wikipedia maintenance]] [[Category:Pronunciation cleanup]]

Notes

External links

Wikimedia documentation on categorization: https://www.mediawiki.org/wiki/Help:Categories