Most of the categories populated by redirect category (rcat) templates are hidden categories. Hidden categories cannot be seen by viewers who are not logged in, nor by editors who have not set their preferences to view them. So if you have tagged a redirect with an rcat and saved the redirect, but you cannot see the category, the first thing to check is if you have set your preferences to view hidden cats:
Some rcats place a redirect in either Category:Printworthy redirects or Category:Unprintworthy redirects by default. Other rcats do not, which means that it is up to editors to choose to the best of their knowledge which of those categories, Printworthy or Unprintworthy, is appropriate and should be populated. The rcats that can be used separately to populate those categories are:
Not all rcats are listed in this functional index; for a complete list of rcats, see the alphanumeric listing.
Notes
{{Redirect category shell}} may be used to add one or more appropriate redirect category (rcat) templates to redirects. Click the template link and read its documentation page for more information. Also, see its comparison page, which illustrates its differences with individual rcat tagging.
For talk pages, there are only certain rcats that should be used. The only rcats that apply to pages in the talk namespaces are {{R from alternative name}}, {{R from shortcut}}, and those associated with moves, merges, disambiguations and cross-namespace redirects. For more information, read the templates' documentation pages. See also {{Talk page of redirect}}.
When rcats are used to categorize image-file redirects, the category(ies) may not appear on the redirect page after saving even if they appeared on preview, and even if preferences are set to view hidden categories. Yet the image-file redirect will still populate the category(ies). For example, in Category:Redirects from moves under the section heading Media in category "Redirects from moves", many image-file redirects have been correctly categorized, and yet for example {{Rcat shell|{{R from move}}{{R from short name}}}}'s categories may not appear on the image-file redirect's page. Hidden categories on image-file redirects can be detected by clicking on "Page information" in the Tools menu on the sidebar.