A piped link is an internal link where the link target and link label are both specified. This is needed in the case that they are not equal, while also the link label is not equal to the link target with the last word extended. This allows linking a word or phrase within the text of a page rather than using "see also", even if the wording does not exactly correspond with the name of the target page. With a suitable browser and depending on the preferences set, one can still see the link target: when you point at the link, the name shows up in a hover box and is also shown in the status bar.
[[recursion|Everything you always wanted to know about recursion]]
Another example would be [[machine vision|vision]] rendering as vision. This is useful where the word "vision" is used in an article on imaging; from the context, it would be clear that machine vision is meant. The piped link is more convenient to the user than a link to vision which might be a disambiguation page.
The term piped refers to the use of the pipe character "|" used to separate the good description from the actual link. This character is named after an alternative use of it; see Pipe Computing.
Using a redirect as an alternative
An alternative is simply using redirect pages. To create Everything you always wanted to know about recursion, use [[Everything you always wanted to know about recursion]] and make this a redirect to recursion (note that, unlike above, what pops up when you point at the link, if applicable for your browser, is simply the text already shown).
This is convenient if the redirect is already there or will also be of use elsewhere; however, there are a few drawbacks:
- the popup does not show the page one will arrive at
- "Related changes" gives the changes in the redirect page not the redirect target
- the redirect message on the target page slightly clutters it
Combining a piped link and a redirect, one can provide some information that is not the name of the page one links to in the hover box, such as the value of a unit in terms of other units. In that case one can make a page whose pagename is the info one wants in the link title, and which redirects to a page with a more appropriate name.
Automatic conversion of the wikitext
If in a piped link the part after the "|" is left empty, it is converted to an abbreviated form of the page name on the left, as follows:
- any word before the first colon ":", as well as the colon itself, is removed. This word may or may not be a namespace prefix (such as "Help:") or an interwiki prefix (such as "commons:"). If the page name is preceded by a colon, "first" refers to "first after this".
- if there is text in parentheses at the end it will be removed
- if there are no parentheses but there is a comma, the comma and everything after it is removed
Just like for the three or four tildes when signing on Talk pages and the use of subst, in a preview, the result already shows up in the preview itself, but the conversion in the edit box is not yet shown. Press "Show changes" to see the change in the wikitext.
- [[Help:Template|]] is converted to [[Help:Template|Template]], which is rendered as Template
- [[Music: My life|]] is converted to [[Music: My life| My life]], which is rendered as My life - although "Music:" is not a namespace (therefore the space after the colon is not automatically removed), the shortcut works anyway
- [[w:en:Pipe (computing)|]] is converted to [[w:en:Pipe (computing)|en:Pipe]], which is rendered as en:Pipe
- [[commons:Boston, Massachusetts|]] is converted to [[commons:Boston, Massachusetts|Boston]], which is rendered as Boston.
For external links a space is used instead of a pipe character; see Help:Editing.