Commons:Category redirects

Category redirects, using {{Category redirect}}, are used on Commons when one category needs to be redirected to another.

Soft redirects need to be used for this purpose instead of normal redirects (with a #REDIRECT), as normal redirects do not behave correctly in category space. For example, if a hard-redirected category is added to any file, then the file does not show in the target category.

Category redirects have a number of disadvantages that mean they should not be used as freely as normal redirects on other Wikimedia projects.

Appropriate uses

It is recommended that category redirects are used in the following circumstances. These redirects should not normally be deleted.

1. [OK] Certain aspects relating to biological taxons, such as when a taxon is monotypic. For example,. Category:Oryctolagus to Category:Oryctolagus cuniculus
2. [OK] Redirects from (English-language) common names for organisms to the scientific equivalent. For example, Category:Crickets to Category:Gryllidae.
3. [OK] When the correct category name uses en dashes, from the equivalent version with hyphens.
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Inappropriate uses

Category redirects should not normally be created in the following circumstances. These may be deleted.

1. Misleading, inaccurate or offensive redirects.
2. When a disambiguation category is more appropriate.
3. From a name with a typographic error to the correct name.
4. Recently created categories that duplicate a pre-existing category.
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Detailed explanation

Advantages

The advantages of using category redirects include:

1. A prominent, auto-translated link is given to the correct target.
2. Prevents incoming links from breaking, especially from other Wikimedia projects.
3. Helps prevent creation of duplicate categories.
4. Helps non-English speakers find the category at its English language name.
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Disadvantages

The problems of using category redirects include:

1. Users are more likely to place files in a category redirect than in a non-existent category.
2. Too many similarly named categories can flood various categoriation tools, such as HotCat.
3. Certain maintenance reports like Special:UnusedCategories become unusable, as category redirects flood them.
4. Special:BrokenRedirects and Special:DoubleRedirects cannot detect problems with category redirects.
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Solutions

There are a number of solutions that address some of limitations above:

1. The best solution of all is a change to Mediawiki to allow redirects to work properly on categories. See this bug report and Summer of Code 2013. If implemented, this will resolve the majority of issues.
2. Bots monitor Category:Non-empty category redirects and move files to the target. This generally takes under 24 hours.
3. The deletion script when a category is moved provides a small, English-language link to the target in a deletion log.
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