Help:Transclusion

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Transclusion refers to the inclusion of the content from one document within another document by reference. In Wikipedia, transclusion means the MediaWiki software retrieving the content from a source page, often a template, and incorporating it into the content of a target page.

Similar to creating a wikilink using double square brackets ([[Pagename]]), a page can be transcluded as a template by enclosing its title in double curly braces or double curly brackets: {{Namespace:Pagename}}. Any changes made to the source page, or template, are automatically reflected on all pages that include the transcluded content.^[a]

If no namespace is specified, it is assumed to be in the Template namespace. To refer to a page in the Main article namespace, it is necessary to prefix it with a colon (:). For example:

• {{Pagename}} is the same as {{Template:Pagename}}
• {{Stochastic processes}} will transclude from the page Template:Stochastic processes
• {{:Stochastic processes}} will transclude from the page Stochastic processes (an article, in the Main namespace)
• {{Wikipedia:Assume good faith}} will transclude from the page Wikipedia:Assume good faith

Transclusion and what content it includes or excludes can be modified by using the invisible wikitext tags <noinclude>, <onlyinclude>, <includeonly>, and <section> on the source page, as further outlined in § Transclusion markup.^[b] The first three tags enable § Partial transclusion, as opposed to the default behavior of double curly braces, which will transclude the entire source page's content. For § Selective transclusion, the <includeonly> or <section> tags can be used and sections of the source page named, then using parser functions the template can be called with the section name as a parameter: {{#section:Pagename|Sectionname}}.

Transclusion events occur each time the target page is loaded and the template is rendered. A related event is Substitution, where a template call is replaced with its transcluded source content at the time it is invoked in a one-time inclusion of the content. Unlike transclusion, which continuously updates the target page with changes from the source, substitution results in a one-time inclusion of the content, meaning that subsequent updates to the source content will not be reflected in the target page. For example, a template call for {{Pagename}} with the subst: prefix results in the substitution template call {{subst:Pagename}}. When invoked, this template is replaced, also referred to as substituted, with the actual wikitext of the source page at the time of the call, thereby making it a permanent part of the target page.^[c]

It is possible to transclude content from Wikidata into Wikipedia articles or other wikis.
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