A Wikipedia shortcut can be entered into the Wikipedia search box to quickly bring you to a reference page.
For example, you can type "WP:R" into the search box and click the "Go" button to get to the Wikipedia "Redirect" reference page, instead of having to type "Wikipedia:Redirect".
Alternatively, you can use the shortcut in the URL (web address). For example, you are currently viewing the Wikipedia:Shortcut page in English. The URL for the English-language page is:
You could get from here to the Wikipedia:Redirect project reference page by replacing "Wikipedia:Shortcut" with "WP:R" in the URL (web address) field (followed by "Enter").
Shortcuts are presented in all capital letters ("All-Caps"), but the search box is case-insensitive. For example, in the search box, you can type "wp:r" instead of "WP:R".
However, using the URL method typically requires that you match the capitalization of the shortcut itself.
A shortcut link box can be added to a page by placing {{Shortcut|[[WP:<x>]]}} at the top of the text while editing. A note from the "shortcut template" page:
Please do not use this template on other templates, e.g. to state that the shortcut to Template:Foo is in fact {{Foo}}. There's no need to state the obvious like that, each template uses its own name as a shortcut, by default.
Technically that's easy, click on the shortcut wherever it is, on the page it leads to (a shortcut is a redirect) click on the "redirected from" link (forcing &redirect=no), edit the target #REDIRECT [[Wikipedia:Whatever]], then add {{R from shortcut}} if that expression doesn't already appear. But there are some potential traps and pitfalls:
If the shortcut is already listed on WP:WP or a similar list like WT:WT please update that entry showing the new target page.
If the old target page mentions its shortcut, then that also should be updated, typically in {{Shortcut}} or similar Wikipedia header templates.
Above all check the shortcut backlinks with "what links here"; changing a shortcut used elsewhere can be highly disruptive.
If it has no backlink folks might still use it directly with search forms, if you're not 100% sure that the old target is unused; so ask about it on the shortcut's talk page.
For controversial cases there is a "redirects for deletion" procedure WP:RFD.
An incomplete list of shortcuts can be found at Wikipedia:Shortcuts, and as expected this page has itself various shortcuts like WP:WP, WP:CUTS, or just WP:.
On Meta shortcuts start with WM:, the list is at m:WM:WM. As shown, links to shortcuts on other projects work as expected, but redirects (incl. shortcuts) to pages on other projects won't work - this former feature was abused and hence it has been disabled.
Use special pages to find uncategorized or unlisted pages starting with a given prefix, e.g. Special:Prefixindex/CAT: for some category shortcuts.
