Help:Template parameters

Templates allow you to pass parameters. These are used to alter the way the template is displayed, such as including specific text or altering the design.

Note: this page describes manipulating templates in source editor. When inserting templates on pages, the VisualEditor can allow you to define and insert parameter text without touching wikitext.

Simple parameters
For small templates, using basic, unnamed parameters will often suffice. These parameters are numbered rather than named, using,  ,  , and so on.

Guide
This guide will walk through creating a basic box template with simple parameters:
 * Create a page on your wiki with a basic name (for instance, "Template:Box"):
 * Add the following code to that page:


 * Save the page to see that it displays the following content:
 * 


 * Create an article page on your wiki called
 * Enter the following code on that page to display your template:


 * Save the page and note that it displays the following content:
 * Example content

Understanding what happened
This replacement happened because  tells the wiki to pass the first parameter of the template here. This can be extended with,  , etc.

The number represents the number of the parameter:

Named and default parameters
For more complex templates, it is often better to use named parameters. This allows for more freedom in how templates are created, and also makes templates easier to use as users will know which parameter affects which element.

Guide
This guide will walk through using named parameters to the above "Template:Box" example:
 * Using the same example pages as before, edit "Template:Box" and replace the content with the following code:


 * introduces the concept of a named parameter.  also introduces the concept of a default parameter: if "bgcolor" is not defined, " " will be used.


 * Edit the page "Template test" and replace it with the following code:


 * Save your page, and note that it displays the following:


 * A navy blue box

Understanding what happened
As the parameters have names, you can pass them in any order, so  would produce an identical box.

Due to default parameters, if, say, the background color was not defined - as in  - you would get:


 * A navy blue box

Named parameters are frequently written on separate lines or with space between parameter name and "=" sign, to aid readability. Generally, this is done in a big template composed of many parameters. It is not unusual to see them written in this form:

A default parameter can be left blank if you do not want an optional parameter to insert anything on a page.

For example, if you wrote  in a template, but did not include a " " input on the article page, it would show up as "". However, if you wrote  in the template, the default is no text, so nothing would show up on the article page.

It is also possible to set another parameter as the default of a parameter, like. This way, if an editor uses, they will get the same output as. This means that a template will default to the  parameter, but if it cannot find  , it will use the unnamed parameter instead; if it cannot find  , it will use no text.

Skipping a parameter
In some templates there may be parameters that are optional - may be supplied or not supplied.

When creating such a template, it is recommended to either use a named parameter for the optional one or to make it the last one so that users can just not supply it. If it is not named and not the last one, there is no easy way to skip it. A user can supply an empty value like

but this may not work as intended, depending on the template, because empty values behave different than non-supplied values. For example, default values are not used because the parameter has been supplied, just with an empty value.

If a template uses optional unnamed parameters and it is necessary to skip an unnamed parameter, it is possible by using explicit numbers for all parameters, like

Another alternative is that the template will check specifically for empty parameters by using conditional Parser functions.

Next steps
Now that you learned what are template parameters, you should learn how to use Parser functions.

You should also learn how to document the template's parameters.