Help:Link
This page contains technical help on making hyperlinks in Wikipedia, giving readers one-click access to other Wikipedia pages, other Wikimedia projects and external websites. For very basic information, see the Cheatsheet. For guidelines on how links should be used in Wikipedia, see Wikipedia:Manual of Style (linking).
Wikilinks
A wikilink or internal link links a page to another page within English Wikipedia.
- [[a]] gives a (link to a, labeled a).
- [[a|b]] gives b (link to a, labeled b). To learn how to type the vertical bar ("pipe" symbol) see Wikipedia:Piped link
- [[a]]b gives ab, just like [[a|ab]] does: ab.
- [[a|b]]c gives bc, just like [[a|bc]] does: bc.
- [[a]]:b gives a:b (punctuation is not appended to the link). The same goes for [[Washington]]'s or e-[[mail]].
- a[[b]] gives ab.
- [[a]]<nowiki>b</nowiki> gives ab.
- [[a]]''b'' gives ab.
- ''[[a]]''b gives ab.
- [[a|b]]c<nowiki>d</nowiki> gives bcd.
Links with a specified label are said to be "piped" because of the pipe symbol used ( | ). For certain types of link, the label will be generated automatically if a pipe is typed with no label after it (thus saving you typing). See Help:Pipe trick.
The link target is case-sensitive except for the first character (so atom links to Atom, but ATom does not). Other ways in which link targets are reinterpreted are described below under Conversion to canonical form.
If the target of a wikilink does not exist, it is displayed red, and is called a red link. If a red link is clicked, the user is taken to a page where it is possible to create a page under the redlinked title. Red links to a particular (non-existent) title can be detected using the What links here feature.
If the target of a link is the same as the page on which it appears (a self-link), it is displayed in bold, as in Help:Link.
Attempting to link normally to an image page, category page or interlanguage link will produce a different effect: it will place the image on the page, add the page to the category or create an interlanguage link at the edge of the page. To override this behavior, add an initial colon, as in [[:File:Mediawiki.png]], [[:Category:Help]], [[:fr:Help:Link]].
Interwiki links
An interwiki link links to a page on another Wikimedia project website, such as Meta or another language Wikipedia. The target site must be on the interwiki map specified for the source wiki. These links have the same [[...]] syntax as wikilinks (see above), but take a prefix which specifies the target site. For example, [[m:Help:Link]] links to the "Help:Link" page on Meta. Links can be piped as with wikilinks. Remember that an interlanguage link should be preceded by a colon if it is to be displayed where it appears in the text; otherwise it will be listed at the side of the page (which is appropriate only if it is the most closely corresponding page in the other language Wikipedia).
Interwiki links (like external links) are displayed in a slightly paler blue than ordinary wikilinks. MediaWiki does not detect whether these target pages exist, so they are never displayed red.
External links
External links use absolute URLs to link directly to any webpage. These links have the associated CSS class "external". External links are in the form [http://www.example.org link name] (resulting in link name), with the link name separated from the URL by a space. Links without link names appear numbered: [http://www.example.org] becomes [1]. Links with no square brackets display in their entirety: http://www.example.org .
See Linking to URLs for more detailed information.
Special:LinkSearch finds all pages linking to a given site.
The external link syntax can also be used to link to particular page versions within Wikipedia that are not accessible by wikilinks, such as page history, edit view, an old version of a page, the diff between two versions, etc. It can also be used to create a navigational image.
To display a link without the arrow icon, place the external link syntax between <span class="plainlinks">...</span> tags.
Section linking (anchors)
To link to a section in the same page you can use: [[#section name|displayed text]], and to link to a section in another page: [[page name#section name|displayed text]].
The section title in fact points to an anchor on the target page. It is possible to define anchors other than explicit section titles, using the HTML code <span id="anchor_name">...</span>, or the template {{Anchor|anchor name}} (see Template:Tl syntax). However [[#top]] and [[#toc]] are reserved names that link to the top of a page and the table of contents, respectively.
Section links still work if the wikilink is a redirect (for example, if Danzig redirects to Gdańsk, then Danzig#History will link to the "History" section of Gdańsk). It is also possible to put section links inside redirects (these work only if JavaScript is enabled). For example, Wikipedia:Section link redirects to Help:Link#Section linking (anchors). Note that an explicit section link overrides any section link in a redirect, so Wikipedia:Section link#Interwiki links will go to the "Interwiki links" section of this page.
For more information, see Help:Section. See also WP:TARGET.
Anchor links can also be added to external URLs and to interwiki links, again using the # syntax. Note that if the page name is automatically converted, then the section link still works, but disappears from the address bar (this makes it more difficult to bookmark the section itself).
Subpage links
In a namespace in which the subpage feature is enabled (which does not include Wikipedia article space), the following relative links can be used:
- [[../]] links to the parent of the current subpage, e.g., on A/b it links to A, on A/b/c it links to A/b.
- [[../s]] links to a sibling of the current subpage, e.g., on A/b, it links to A/s.
- [[/s]] links to a subpage, e.g. on A it is the same as [[A/s]].
More details can be found at m:Help:Link#Subpage feature.
ISBN, RFC and PMID automatic links
Links to these items are generated automatically, with no need to insert square brackets:
- ISBN codes automatically generate links, for example: the wikitext
ISBN 978-0-12-345678-9becomes ISBN 978-0-12-345678-9 which corresponds to Special:Booksources/9780123456789. RFC 4321becomes RFC 4321, which is the external link to the standard at:http://tools.ietf.org/html/rfc4321.PMID 12345678becomes PMID 12345678, which links to a reference in the medical literature at PubMed.
To prevent such automatic linking, use <nowiki>...</nowiki> tags around the text.
Changing link appearance
The ways that various links are displayed in browsers, as described above, are the default display styles in the default skin. Users can change the way they see links:
- by selecting a different skin;
- by applying a user style using CSS;
- by changing the "Underline links" or "Format broken links like this" value on the Appearance tab of user preferences;
- by setting the "threshold for stub display" on the Appearance tab of user preferences. This causes links to pages in mainspace to be displayed in a distinctive fashion – dark red by default – if the wikitext of the target page has less than a specified number of bytes. (Any section markers in the link are ignored. Links to redirects are displayed in the normal style).
Hover boxes
In many browsers, holding the cursor over a link (mouseover) shows a hover box (tooltip) containing the text of the link's HTML title attribute. MediaWiki sets this to the target page name (without any section indication) if it's a wikilink, the page name with prefix if it's an interwiki link, and the URL if it's an external link. (This can be switched off in the user preferences.) The browser may also show similar information, including any section indication, in the address bar.
For these effects a piped link is useful even if it is not followed; for example, for displaying the meaning of an acronym. It is possible to produce a hover box without a link, using the Template:Tl template.
Disallowed characters
A link whose target contains disallowed characters (see WP:Page name) will be displayed without markup, as in [[A{b}]].
Conversions are automatically made to non-literal characters in wiki and interwiki links. For example, "[[Help:Page%20name]]" becomes "Help:Page name". However, the opposite is true for external links; literal characters are converted into non-literal characters. For example, most browsers convert ".../wiki/!" to ".../wiki/%21".
A code like %70 in a redirect disables it, although the link works from the redirect page. For a redirect that works, the redirect page shows the canonical form of the target, unlike its preview page, which renders the link in the usual way.
Links containing URL query strings
Because the ampersand character (&) is disallowed, it is not possible to create an ordinary link containing &action=edit or &redirect=no in the URL query string. These kinds of links can be helpful in user pages. Also, a redirect page can have categories and you might wish to view or edit these in a single click.
The following syntax shows the use of the magic word fullurl as it would appear in a template constructed to append action=edit to the URL query string:
[{{fullurl:{{{1}}}|action=edit}} {{{1}}}]
Note that this will render as an external link rather than as an internal link and for this reason it might not appear in what-links-here queries associated with the target page.
Links to and from a page
To list pages which link to the current page (backlinks), use the What links here feature. The Template:Tl tag can be placed on pages with few incoming links.
To make the current page show up at "What links here" for a certain other page without creating a working link to that other page, use a link with a space following the pipe, as in [[Main page| ]].
To list all pages which are linked from a particular page, enter the following URL, using the page title (with spaces replaced by underscores) in place of PAGENAME:
http://en.wikipedia.org/w/api.php?action=query&prop=links&pllimit=500&titles=PAGENAME
The number of links returned is limited to 500.
For the effect that links have on date formatting, see Help:Date formatting and linking.
Another link-dependent feature is Related changes, which makes it possible to view recent changes to all pages which are linked from the current page (or which are members of the category, if it is a category page).
For information on how to link to pages from an image, see mw:Extension:ImageMap.
Several templates have been created to make linking easier (although they are not usually used in article space). These include Template:Tl and Template:Tl for linking to templates, and Template:Tl and Template:Tl for linking to categories. More can be found in Category:Internal link templates.
Conversion to canonical form
As described above, if a link target begins with a lower case letter, it will be interpreted as if it began with the equivalent capital letter. If the target contains a namespace prefix, then the whole prefix and the first character after the colon are case-insensitive (so uSeR:jimbo Wales links to User:Jimbo Wales).
In link targets, spaces and underscores (which are effectively equivalent) are ignored if they come at the start, at the end, or immediately before or after the colon following a namespace prefix. Consecutive spaces/underscores are treated as a single space. Hence _User_: Jimbo_ __ Wales__ links to User:Jimbo Wales.
Also, HTML character references and percent-encoded characters are replaced with their raw character. For example, [[département]] produces département, and [[%40]] produces @. Links which resolve to invalid page titles are displayed as unmarked-up wikitext.
Titles indicated by wikilinks are displayed in canonical form (with correction of capitalization and excess spaces/underscores removed, as described above) in the following places:
- in transclusion tags for non-existent pages: {{qwsazx}} gives Template:Qwsazx;
- in pop-ups and on the status bar (if applicable for the browser) when the mouse cursor is moved over the link;
- on redirect pages;
- in the category box.
The prefixes in interwiki links are treated similarly to namespace prefixes: they are insensitive to case and to spaces before and after the colon. However the first character after the colon is not automatically capitalized (whether it is interpreted as a capital depends on the configuration of the target wiki).
See also
Link. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Link&oldid=19457