Transclusion


 * Detailed reference page on this subject: Help:Template.

Transclusion refers to the process by which the entire contents of a page are inserted on to another page for the sake of convenience, speed of editing and/or tidiness of the source wikitext. The process works by applying the title of the page to be transcluded, with two braces  on either side and sometimes a colon.

Templates
Pages created for the sole purpose of being useful to transclude are known as templates. Templates come in many varieties; some templates constitute generic messages that can be quickly and easily sent, while others contain pieces of text that are used in mass quantities. The use for these quick pieces of text or code are almost limitless, and there are literally hundreds of thousands in current use all over Wikimedia. They have their own namespace, Template:.

While the braces assume, and it is implied, by default, that the template namespace is to be transcluded (ie: the syntax assumes that, if is applied, then it is in reference to Template:FOO by default), all kinds of pages, in every namespace, so long as the namespace is specified:  would be a viable and workable transclusion. Because of template: vs (main) confusion when transcluding, pages with no namespace prefix, such as this one, are transcluded like this, with a colon preceding the page name:.

Link that is created
It is important to remember that transclusion creates a very real and direct link between the target page and the transcluded one; when the source page is changed, the transcluded text is changed with it. This especially applies to templates that are in mass use; many pages can be altered very radically by a small change. The volatility of this situation should be considered when making changes.

It is possible to see what pages are transcluded on a page, and where a page is transcluded, by use of the "What links here" link in the toolbox in the left hand panel.

Examples
The following is an example of transclusion Information thread:

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Viewing that source will show that while that thread is complex, with a fair bit of text and a lot of use of code, all it takes is a simple application of here to transclude accurately, how it displays there. This is very handy for managing information on the wiki.