Help:Templates

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If you have standard texts you want to include on several pages, the MediaWiki template feature comes into play.

Creation

Templates are standard wiki pages whose content is designed to be transcluded (embedded) inside other pages. Templates follow a convention that the name is prefixed with "Template:", assigning it to that namespace; besides this, you can create them like any other wiki page.

The simplest use of templates is as follows. If you create a page called "Template:Welcome" with contents:

Hello! Welcome to the wiki.

you'll have created your first template! If you then insert the code:

{{Welcome}}

in any other page, when that page is viewed the text "Hello! Welcome to the wiki." will appear instead of {{Welcome}}. The template content is "transcluded" into the other page, i.e. it is integrated in the page.

You can then insert {{Welcome}} at any point of any page where you wish to welcome someone. Suppose it is used in 100 pages. If you then change the template contents to:

Hi there! Welcome to this wonderful wiki.

and revisit any of the 100 pages where the template was used, you'll see the new text instead of the original one. In this way, you have changed the content of 100 pages without editing them, because the template is transcluded into these pages.

This is the basic mechanism. There are several additional features of transclusion that enrich this mechanism and make templates very useful.

Usage

Templates can be used in other pages in these ways:

  • {{Name}}, described above, 'transcludes' (i.e. includes a copy of) the content of the template (stored in the page [[Template:Name]]) whenever the page containing the template transclusion is fetched and displayed; i.e. if the template is later changed, the displayed transcluding page will automatically change too
  • {{subst:Name}} replaces that string with the contents of the template, in the source of the transcluding page, when you save that page; the copy of the template contents can then be edited normally (and separately from the original in the template page). Note: don't use this if you are looking to continually propagate changes from the source template to the page(s) that references it.
  • {{safesubst:Name}} was introduced in rev:61710 to allow for substitution that doesn't break transclusion, see The safesubst: modifier.
  • {{msgnw:Name}} includes the template in a form that displays it as raw wiki syntax (the way <nowiki> does) when the page containing it is fetched.

In fact, an ordinary wiki page can also be used as a template, simply by specifying the namespace it resides in, so:

  • {{Template:Pagename}} includes [[Template:Pagename]]
  • {{Foo:Pagename}} includes [[Foo:Pagename]]
  • {{:Pagename}} includes [[Pagename]]
    • {{subst::Pagename}} replaces itself with the contents of [[Pagename]]

If no such namespace exists, the full title is assumed to be a template:

  • {{Foo:Bar}} includes [[Template:Foo:Bar]]

Full syntax for transcluding and substituting

The basic transclusion syntax given above can be extended by the addition of parameters, which are used to control the template's output. The syntax for this is

  • {{template name|parameter|parameter|...}}

where each "parameter" may either contain just a value (these are called unnamed parameters) or be of the form name=value (named parameters). The first, second, etc. unnamed parameters are equivalent to parameters named "1", "2", etc.

Whitespace characters (spaces, tabs, returns) are stripped from the beginnings and ends of named parameter names and values, but not from the middle: thus {{ ... | myparam = this is a test }} has the same effect as {{ ... |myparam=this is a test}}. This does not apply to unnamed parameters, where the whitespace characters are preserved.

What parameters (if any) can or should be passed to a template, and how they are to be named, depends on the coding of that template. Named parameters can be defined in any order. Superfluous or misnamed parameters will be ignored; undefined parameters will be assigned default values. If a parameter is defined more than once, the last value takes effect.

The value of a parameter can be the empty string (pipe or equals sign followed immediately by the next pipe or the closing braces). This is different from leaving the parameter undefined (although templates are often coded so as to behave the same in both cases).

If a template is to be substituted in the wikitext rather than transcluded, add the modifier subst: after the initial pair of braces, as in {{subst:afd}}. Parameters can be added as above. (If substituting a page from mainspace, the word "subst" must be followed by two colons.)

Template names are exactly like other page names: case-sensitive except for the first letter, with spaces indistinguishable from underscores. If the symbol # (normally used to link to a section of a page) appears in a transclusion, then it and any characters that follow it are ignored. If the page name used for transclusion is a redirect, the redirect target will be transcluded instead — this means that alternative names can be created for templates.

Notice that the same double-brace syntax is used for many MediaWiki variables and parser functions (see Help:Magic words). For example, the code {{NAMESPACE}} may look like a template call, but it is actually a variable whose value is the namespace prefix of the current page.

Parameters

To enrich the mechanism of transclusion, MediaWiki allows parameters to be passed to a template when it is transcluded. Parameters allow the template to produce different contents or have different behaviors.

Suppose you wish to insert a little thank you note in the talk page of other users, such as:

Logoog.png
A little thank you...
for all your effort.
hugs, Me


The thank you note will have a reason (in this case, "all your effort") and a signature ("Me"). Your objective is that any user is able to thank any other user, for any reason whatsoever.

So that the note will look similar everywhere it is used, you can define a template called Template:Thankyou, for example. Although the note should look similar whenever a user thanks another user, its specific contents (i.e. the reason and the signature) will be different. For that reason, you should pass them as parameters. If we ignore the remaining elements to format the box and place the image, the core content of the template will be this:

'''A little thank you...'''
for {{{1}}}.
hugs, {{{2}}}

Notice the use of {{{1}}} and {{{2}}}. This is the way to identify, within templates, the parameters that will be passed in when the template is used. Note that, within the template, each parameter is surrounded by three braces: {{{ }}}. This is different from normal template name usage.

When using the template on a page, you fill in the parameter values, separated by a pipe char (|). MediaWiki allows parameters to be passed to the template in three ways.

Anonymous parameters

To pass in anonymous parameters, list the values of those parameters sequentially:

{{Thankyou|all your effort|Me}}

In this case, template {{Thankyou}} receives parameters {{{1}}}=all your effort and {{{2}}}=Me and produces:

Logoog.png
A little thank you...
for all your effort.
hugs, Me



Inverting the order of the parameters:

{{Thankyou|Me|all your effort}}

causes template {{Thankyou}} to receive parameters {{{1}}}=Me and {{{2}}}=all your effort and inverts the result:

Logoog.png
A little thank you...
for Me.
hugs, all your effort


So, the order in which anonymous parameters are passed in is crucial to its behaviour.

Numbered parameters

To pass in parameters by number, identify each parameter when passing it:

{{Thankyou|2=Me|1=your friendship}}

This time, template {{Thankyou}} receives parameters {{{1}}}=your friendship and {{{2}}}=Me, though they have been supplied in inverse order, and produces:

Logoog.png
A little thank you...
for your friendship.
hugs, Me



Named parameters

The third way of passing parameters is by name, instead of numbers. In this case, the template contents would be changed to:

'''A little thank you...'''
for {{{reason}}}.
hugs, {{{signature}}}

Within the template, we use {{{reason}}} and {{{signature}}} to identify each parameter, instead of a number. To pass these parameters by name, identify each parameter when passing it:

{{Thankyou|signature=Me|reason=being who you are}}

In this case, template {{Thankyou}} receives parameters {{{reason}}}=being who you are and {{{signature}}}=Me and produces:

Logoog.png
A little thank you...
for being who you are.
hugs, Me


The advantage of using named parameters in your template, besides also being flexible in the order parameters can be passed, is that it makes the template code much easier to understand if there are many parameters.

Default values

If you transclude a template that expects parameters, but do not provide them, in this way:

{{Thankyou}}

in the numbered parameters example above you would get the following:

Logoog.png
A little thank you...
for {{{1}}}.
hugs, {{{2}}}


Since no parameters were passed in, the template presents the parameters themselves, instead of their respective values. In these cases, it may be useful to define default values for the parameters, i.e. values that will be used if no value is passed in. For example, if the template contents are changed to:

'''A little thank you...'''
for {{{reason|everything}}}.
hugs, {{{signature|Me}}}

then {{{reason|everything}}} defines that if no parameter {{{reason}}} is provided, then the value everything will be used. Similarly, {{{signature|Me}}}, defaults parameter {{{signature}}} to value Me. Now, transcluding the template again without passing any parameter, results in the following:

Logoog.png
A little thank you...
for everything.
hugs, Me



Control template inclusion

By default, the whole content of a template will be processed and displayed both when the template page is being viewed directly and when the template is being included in another page. However, you can control template inclusion by the use of <noinclude> and <includeonly> tags.

Anything between <noinclude> and </noinclude> will be processed and displayed only when the template's page is being viewed directly, and will not be processed and displayed when it is included in another page. The application of this is to do things to the template page that should not be similarly done to the pages where it is included:

  • Categorising the template.
  • Placing in the template interlanguage links to similar templates in other languages.
  • Presenting explanatory text about how to use the template.

Anything between <includeonly> and </includeonly> will be processed and displayed only when the page is being included, and will not be processed and displayed when the template page is being viewed directly. The application of this is to do things in the pages where the template is included that you do not want to be similarly done in the template page:

  • Categorising only the pages where the template is included. Note that when you change the categories applied by a template in this fashion, the categorization of all the pages where that template is included may not be updated until some time later: this is handled by the job queue. To force the re-categorisation of a particular page, open the page for edit and save it without changes.
  • Ensuring that the template's code is not executed when viewing the template page itself. Normally this is because it isn't receiving any parameters and its execution without parameters has an undesired aspect.

Of course, everything outside <noinclude> and <includeonly> tags is processed and displayed both when the template page is being viewed directly and when the template is being included in another page.

Organizing templates

For templates to be effective, users need to find them, and find out how to use them.

To find them, users can:

  1. Click Special Pages > All Pages
  2. In the Namespace list, choose Template and click Go.

To give usage information, include an example like this one on the template page:

<noinclude>
== Usage ==
Welcome users:
{{Thankyou|reason=your reason|signature=your signature}}
</noinclude>

Then, an editor can simply copy and paste the example to use the template.

Documentation

Template:Wikipedia how to

Templates are a very powerful feature of MediaWiki, but can be confusing to new users and even experienced users can have difficulty making sense of the more complex ones. Templates should therefore be accompanied by documentation to improve usability.

Template documentation should explain what a template does and how to use it. It should be simple enough that a user without complete knowledge of the intricacies of template syntax – which includes many experienced contributors who focus their attention elsewhere – can use it correctly. This is especially true in the case of very widely-used templates.

What to include

Template documentation should cover:

  • The basic purpose of the template: what it does and if it is not immediately obvious, why it needs to be done. If there are other templates with similar names or purposes, it's a good idea to mention those, in order to reduce the chance of the wrong one being used.
  • The parameters of the template: whether they are numbered, named or optional, and if so, what the default values are and what effect they have. If a parameter can take only a limited set of values or is constrained in any way, for example, if it can only use: “yes”, “no” or a number, this should be clearly explained.
  • Usage examples: specify the exact wikitext that should be used and the result that it produces. The wikitext can be enclosed in a <code>…</code> container, to make it clear and easy to copy, like this. If the template can be used in several different ways, with or without optional parameters, for example, provide a range of examples. A good way to do so is to transclude the template itself into the documentation a few times (i.e., use live examples), with different parameters each time and list the parameters used in each case. With Template:Xpd this can be done without putting the template call twice in the wikitext.
  • Related templates: if the template is one of a series of templates, include links to these – in particular, ensure that every template in the series is linked from each of the others, as this makes navigation easier. (A separate navigation template may be useful for this purpose, see: Template:Protection templates).
  • Categories and InterWikimedia links, where applicable. Like the documentation, these must be within a <noinclude>…</noinclude> container. Many template categories are available, see: Category:Project templates to browse through them.

Template documentation is often placed in a subpage of the template itself, which is then transcluded at the end of the template page. This separates the often complex template code from the documentation, making the documentation easier to edit. It also allows templates to be protected where necessary, while allowing anyone to edit the documentation. This method is sometimes referred to as the “template doc page pattern”.

Documentation of any sort on a template page should always be enclosed by a <noinclude>…</noinclude> container, so that it does not show up when the template is used on another page. Text on the template page itself adds to the amount of text that must be processed when displaying the template, which is limited for performance reasons. Placing the documentation in a subpage avoids this (MediaWiki developers have recommended it for this reason).

How to create a documentation subpage

Template documentation subpages should be named and formatted using the following general pattern, for consistency.

Suppose your template is named Template:X. Create a subpage with the name Template:X/doc. See the details at {{Documentation subpage}} or copy-paste the following wikitext as a start for your documentation:

{{Documentation subpage}}
<!-- Categories and interwikis go at the bottom of this page. -->

== Usage ==

== See also ==

<includeonly>
<!-- Categories and interwikis go here: -->

</includeonly>

The top line will display a message explaining the current page and a link to the template page.

Insert the documentation after the top line and categories and interwikis under the appropriate comment line – leaving the comment in place, so that the layout is preserved when the page is edited in future. The subpage template sets a {{DEFAULTSORT:{{PAGENAME}}}}, ensuring that a Template:X will be properly sorted at "X" and not "T", it is thus not useful or desirable to add a {{PAGENAME}} sortkey to the categories. Related templates, policy page, projects, etc. can be linked to under "See also", or just comment-out this section heading if it isn't needed (yet): <!-- ==See also == -->

Save the subpage and return to the template itself, Template:X, in this example. Edit the template and append the following at the end of the template code:

[--last line of your template code--]<noinclude>

{{Documentation}}
<!-- PLEASE ADD THIS TEMPLATE'S CATEGORIES AND INTERWIKIS TO THE /doc SUBPAGE, THANKS -->
</noinclude>

This will transclude {{Documentation}} at the bottom of the template page.

Important: Make sure the opening <noinclude> begins on the same line as the last character of the template code or text and not on a new line. Otherwise, extra space will be inserted below the template when it is used, which is usually not wanted.

If the template is already protected, ask an administrator to do this or request an edit by using an {{Editprotected}} on the template's talk page. If documentation, categories and interwiki links already exist in a section, enclosed within a <noinclude>…</noinclude> container, move them into the documentation subpage, as it is best not to have documentation split across two separate pages.

If the code is put on the template page first, one can benefit from the preload feature to get a pre-filled doc page skeleton; if the documentation page does not exist yet, clicking the edit link on the template page will preload the contents of Template:Documentation/preload into the editbox of the /doc subpage creation.

You may wish to redirect the talk page of the /doc subpage to the talk page of the template itself. Then all talk relating to the template and its documentation will end up on the same talkpage. For example, redirect Template talk:X/doc to Template talk:X.

Categories and interwiki links

  • To place the template itself into a category, add the [[Category:Category name]] code inside an <includeonly>...</includeonly> section on the doc subpage.
  • To create an interwiki link for the template itself, add the [[Languagecode:Template name]] code inside an <includeonly>...</includeonly> section on the doc subpage.
  • To place the doc subpage into a category, add the [[Category:Category name]] code inside a <noinclude>...</noinclude> section on the doc subpage.
  • To make the template place an article into a category (when the article includes the template), add the [[Category:Category name]] code inside an <includeonly>...</includeonly> section on the template page.

Example

See the heavily-used Template:cite web for an example of detailed template documentation. Note that the template itself is protected, but the documentation subpage, Template:cite web/doc is unprotected and can still be edited.

/sandbox and /testcases

Before doing changes to a template it can be good to first copy the template code to a sandbox and run some testcases, since the template might be visible on thousands of pages. If you create subpages named exactly "/sandbox" and "/testcases" to a template then the green {{documentation}} box on the template auto-detects this and will show links to those pages in its header. See Wikipedia:Template test cases for more information.

Several templates, one documentation page

When several templates work together or are very similar then it is often clearer and easier to maintain one single documentation page that documents them together. The simplest way to do this is to make a full documentation page at one of the templates, and then make "soft redirects" from the other templates. That is, to make very short documentation pages at the other templates that have only one or two sentences that states where the full documentation can be found and link to it. See for instance {{wrap}}.

Stub templates

Stub templates are one of the very rare forms of template that do not generally have documentation. As all stub templates operate in identical ways, they could theoretically be linked to one documentation page giving instruction for their use. This is, however, regarded as superfluous, since all stub templates already contain a link to Wikipedia:Stub, which more thoroughly covers all the information that would normally be covered by a documentation page.

For documentation see also

Copying from one wiki to another

Templates often require CSS or other templates, so users frequently have trouble copying templates from one wiki to another. The steps below should work for most templates.

MediaWiki code

If you have import rights on the new wiki:

  1. Go to Special:Export on the original wiki, and download an .xml file with the complete history of all necessary templates, as follows:
    • Enter the name of the template in the big text box.
    • Check the box "Include templates".
    • Uncheck the box "Include only the current revision".
    • Click Export.
  2. Go to Special:Import on the new wiki and upload the .xml file.

If you don't have import rights on the new wiki:

  1. Go to Special:Export on the original wiki, and download an .xml file with the latest version only of all necessary templates, as follows:
    • Enter the name of the template in the big text box.
    • Check the box "Include templates".
    • Check the box "Include only the current revision".
    • Click Export.
  2. Open the file in a text editor and manually copy the text inside the <text> tag of each listed template into a similarly named template in your wiki. In the edit summary of each template, link to the original page for attribution.

This will copy the entire code necessary, and will suffice for some templates.

Extensions

An extension often used in templates is ParserFunctions. Visit page ParserFunctions and check if any of the functions listed there are used in the templates you've copied. If so, you have to install the ParserFunctions extension. To install it, you'll need system admin access to the server of your MediaWiki instalation.

CSS and JavaScript code

Besides MediaWiki code, many templates make use of CSS and some rely on JavaScript to work fully. If the copied templates are not behaving as expected, this may be the cause. To copy the required CSS and JavaScript to your wiki you'll normally need to have admin priviledges, because you'll be editing system messages in the "MediaWiki:" namespace.

  1. Look for the use of CSS classes (text like class="foobar") in the template text. If those classes appear in "MediaWiki:Common.css" or "MediaWiki:Monobook.css" on the original wiki, copy them to "MediaWiki:Common.css" on the new wiki and check if the template is now fine.
  2. If the copied template is still not working as expected, check if there is code in "MediaWiki:Common.js" or "MediaWiki:Monobook.js" on the original wiki. If so, you can try copying it to "MediaWiki:Common.js" on the new wiki. Normally, it is a good idea to only copy code from trusted sources, and first browsing the code to identify and select the parts that seem relevant. You may find comments that can serve as clues to identify the functionality of each part. When in doubt, copy all the code to the new wiki.

Edit notices

MediaWiki contains various features to display a custom notice above the edit form, depending on the page, namespace, or other circumstances. Below are the most important ones.

Editnotice (added in rev 1.14)
This is a per-namespace and per-page notice, only loaded in the content language.
The page "MediaWiki:Editnotice-N" is loaded for an entire namespace, where "N" is the namespace number. For example "MediaWiki:Editnotice-3" is loaded for user talk pages.
Each distinct page can have a specific notice via "MediaWiki:Editnotice-N-Title", where "N" is again the namespace number. Note that slashes (/) are replaced by hyphens (-). For example, "MediaWiki:Editnotice-2-Joe-sandbox" corresponds to both "User:Joe-sandbox" as "User:Joe/sandbox".
Talkpagetext
The message "MediaWiki:Talkpagetext" is loaded on any talk page as well. This corresponds to all "MediaWiki:Editnotice-X" messages together, where X is is an odd number. This message can be customized per user language.
It can contain for example recommendations regarding etiquette (or a link to a page where it is addressed) and a reminder for the users to always sign their posts with four tildes.
Editinginterface
The message "MediaWiki:Editinginterface" is displayed while editing MediaWiki messages, above "MediaWiki:Editnotice-8" (8 is the namespace number of the MediaWiki namespace). This message, however, contains text by default and is translated into the user language.
Creating new pages
While creating a non-existing page, the user interface message "MediaWiki:Newarticletext" is displayed.

High-risk templates

Following project protection policy, page protection may be indefinitely applied to all templates and template redirects that have been identified by the community as being of high risk to Wikipedia. If fully protected, so that they can only be edited by administrators, or template-protected, so that they can only be edited by administrators and template editors, these templates should be changed only after consensus for the change has been established on the template's talk page. If semi-protected, templates may be edited by any established user, but users should ensure there is consensus for their edits and avoid edit wars on templates.

The most common reasons a template is considered high-risk are:

  • The template is used in a permanently highly visible location, and it isn't cascade protected.
  • The template is transcluded into a very large number of pages.
  • The template is substituted extremely frequently on an ongoing basis (for example, templates used to warn users about inappropriate editing).

There are no fixed criteria, and no fixed number of transclusions, that are used to decide whether a template is high-risk. Each template is considered separately. If a template relates to a biography of a living person that would strengthen any arguments in favor of (preemptive) protection of the template.

Usage hints and workarounds

The following points may be worth noting when using templates:

  • An unnamed parameter cannot contain an ordinary equals sign, as this would be interpreted as setting off a named parameter. (This does not apply if the equals sign comes within another template call or other item which the parser handles separately.) To pass an equals sign in an unnamed parameter (for example in a URL with key/value pairs), replace the equals sign with the special template {{=}}, which returns an equals sign that will not be specially interpreted. Another method is to replace the unnamed parameter (and any subsequent unnamed parameters) with named parameters — the first unnamed parameter is equivalent to a named parameter with the name "1", and so on. So to call template {{done}} with the parameter "a=b", type either {{done|a{{=}}b}} or {{done|1=a=b}}.
  • Similarly, it is not possible to use an ordinary pipe character | in template parameters, as it will be interpreted as a separator. (Again, this does not apply if it comes within another separately parsed item, such as a piped wikilink.) This time the problem can be solved by using the special template {{!}} in place of the pipe, or (if the pipe is not intended to be parsed specially at a higher level) using the HTML entity &#124;.
  • Remember that whitespace characters (spaces, tabs, carriage returns and line feeds) are not automatically stripped from the start and end of unnamed parameters (as they are from named parameters). Including such characters (or any other non-visible characters in any parameters) may in some cases affect the template's behaviour in unexpected ways. (Template designers can use {{StripWhitespace}} to remove unwanted whitespace in unnamed parameters.)
  • In documentation and discussions it is often convenient to be able to produce the template call syntax, with a link to the template in question, but without actually calling the template. This can be done easily using the "{{tl}}" template (the template link template). For example, using the text "{{tl|tc}}" produces "{{tc}}". There is an extended version, {{tlx}}, which also supports parameters.
  • When a template is changed (when the template or one of its subtemplates is edited), the change will be reflected on all pages on which the template is transcluded. However the change may not become visible on all pages immediately — a previously cached version of a page, based on the previous version of the template, may continue to be displayed for some time. Use the purge function to force a page to be displayed using the latest versions of templates. (This includes the template page itself, if it contains usage examples.)
  • When viewing old versions of pages, remember that templates will be transcluded as they are now, not necessarily as they were when the old page version was active.
  • To list all pages onto which a template is transcluded, use What links here on the template page. (This will not include pages where the template has been substituted.)
  • To get a list of templates transcluded on a page, click "Edit", and find the list below the edit window. This list also includes the sub-templates used by the templates that are directly transcluded. To get such a list for a page section, an old version of the page, or your newly edited version prior to saving, click "Show preview" on the appropriate edit page. (For an old version, the subtemplate tree will be constructed according to the templates' current state.)

Specifying parameter defaults

Very often you will see parameters in this form:

{{{A template parameter|}}}

The pipe character "|" is the delimiter for a default value in the parameter. In the example above, it is empty, so the default would be an empty string if no value were passed from the template to the parameter. Of course, you may define a default like this:

{{{A template parameter|with a default value}}}

The string "with a default value" is the default value of the parameter if it is not set elsewhere.

See also

Language: English