MediaWiki Transclusion — Templates, Parameters, Includeonly, and Noinclude

In this tutorial, you will learn about MediaWiki Transclusion. We cover key concepts, practical examples, and best practices to help you master this topic.

Transclusion in MediaWiki is the inclusion of content from one page into another using templates, parameters, inclusion control tags, and partial transclusion — the same mechanism that powers every infobox and navigation template on Wikipedia.

What You'll Learn

• How transclusion differs from copy-pasting
• Creating templates with named and positional parameters
• Using <includeonly>, <noinclude>, and <onlyinclude> tags
• Building a reusable information box
• Documenting templates so others can use them

Why It Matters

Transclusion is the most powerful concept in MediaWiki. Without it, every page that needs a "Note" box or a "Staff" list would require copy-pasting the same code. When you need to change the note style, you would have to edit every page manually. With transclusion, you write the content once and include it anywhere. Change the source, and every page that includes it updates automatically. This is the DRY (Don't Repeat Yourself) principle applied to wiki content.

Real-World Use

A DodaTech wiki has a "System Status" notice that appears at the top of 20 documentation pages. When the system status changes, the wiki admin edits one page — the "System Status" template — and all 20 pages update instantly. A "Quick Links" navigation box on the sidebar of 50 product pages is maintained the same way. Transclusion makes wiki maintenance scalable.

Learning Path

flowchart LR
  A["11: Advanced Wikitext"] --> B["12: Image & Media"]
  B --> C["13: Transclusion"]
  C:::current
  D["14: Parser Functions"]
  E["15: Subpages"]
  F["16: Redirects"]

  C --> D --> E --> F

  classDef current fill#38bdf8,color#0f172a,stroke-width:2px

What Is Transclusion?

The word "transclusion" combines "trans-" (across) and "inclusion" (including). It means including content from one page into another, not by copying it, but by referencing it.

When you write {{PageName}} on a page, MediaWiki fetches the content of "PageName" and inserts it at that point. If "PageName" changes, every page that uses {{PageName}} shows the updated content.

Source page: Template:Notice
  Content: "The system will be down on Saturday."

Destination page: Installation Guide
  Source: "{{Notice}}"
  Rendered: "The system will be down on Saturday."

After editing Template:Notice to say "Sunday" instead of "Saturday":
  Destination page now shows: "The system will be down on Sunday."

No copy-pasting. No manual updates. One change propagates everywhere.

The Three Inclusion Tags

MediaWiki provides three tags that control what happens when a page is transcluded.

<noinclude> — Show on Source, Hide on Target

Content inside <noinclude> tags appears on the source page but is NOT included when the page is transcluded elsewhere.

= Template:Notice =
<div class="notice">System maintenance this weekend.</div>

<noinclude>
[[Category:Notice templates]]
== Usage ==
Use this template to display maintenance notices.
</noinclude>

On Template:Notice, the category link and usage instructions are visible. When {{Notice}} is used on another page, only the div appears — the category and instructions are excluded.

Use <noinclude> for:

• Template documentation
• Categories that should only apply to the template itself
• Interlanguage links for the template page
• Examples showing how to use the template

<includeonly> — Hide on Source, Show on Target

Content inside <includeonly> tags is hidden on the source page but appears when transcluded.

= Template:Version =
<includeonly>Version {{{1}}} (stable)</includeonly>

On Template:Version, nothing is visible (the page appears empty). When {{Version|2.0}} is used on another page, it displays "Version 2.0 (stable)".

Use <includeonly> for:

• Content that only makes sense in context (category tags that should apply to the including page)
• Template logic that should not be visible on the template page itself
• Content that requires parameters to be meaningful

<onlyinclude> — Exclusive Inclusion

Content inside <onlyinclude> tags is the ONLY content included during transclusion. Everything outside these tags is excluded.

= MyPage =
<onlyinclude>
This is the reusable part.
</onlyinclude>

This part is only visible on MyPage itself, not when transcluded.

When another page uses {{MyPage}}, only "This is the reusable part." is included.

Use <onlyinclude> when:

• You want a page that is mostly display content but has a reusable section
• You want to include a specific portion of a page without creating a separate template

Combining Tags

The tags work together for complex scenarios:

<noinclude>
= Template:Infobox Product =
<pre>
{{Infobox Product
|name=Product Name
|version=1.0
}}
</pre>
</noinclude>

<includeonly>{| class="wikitable" style="float:right;width:300px;"
|+ {{{name|Product}}}
|-
! Version || {{{version|N/A}}}
|-
! Status || {{{status|Stable}}}
|}</includeonly>

On the template page, you see documentation and a usage example. When transcluded, only the infobox table appears.

Transclusion with Parameters

Parameters make transclusion dynamic. Instead of showing the same content everywhere, templates accept input.

Positional Parameters

= Template:Greeting =
Hello, {{{1}}}! Welcome to {{SITENAME}}.

Usage: {{Greeting|Alice}} renders "Hello, Alice! Welcome to My Wiki."

Parameters are numbered 1, 2, 3, etc. If not provided, {{{1}}} displays literally. Add a default:

= Template:Greeting =
Hello, {{{1|World}}}! Welcome to {{SITENAME}}.

Now {{Greeting}} renders "Hello, World! Welcome to My Wiki."

Named Parameters

= Template:UserInfo =
{| class="wikitable"
! Name || {{{name}}}
|-
! Role || {{{role}}}
|-
! Department || {{{dept|General}}}
|}

Usage:

{{UserInfo
|name=Alice
|role=Developer
|dept=Engineering
}}

Named parameters are self-documenting — the person using the template can see what each value means.

Default Values

The pipe syntax {{{param|default}}} provides a fallback:

{{{1}}}           Required — no default, shows literal if missing
{{{1|}}}          Optional — empty default
{{{1|N/A}}}       Optional — "N/A" if not provided
{{{name|World}}}  Named parameter with default

Always provide defaults when a parameter is optional. Required parameters should have no default so the template creator sees {{{1}}} in the output if they forget to supply a value.

Partial Transclusion

Sometimes you want only a section of a page, not the whole thing. Use <section> tags with the Extension:Labeled Section Transclusion, or use <onlyinclude> more precisely.

Basic partial transclusion with <onlyinclude>:

= Installation Guide =
== Overview ==
This guide covers installation on Linux.

<onlyinclude>
== Quick Start ==
Run the following command:
<syntaxhighlight lang="bash">
sudo ./install.sh
</syntaxhighlight>
</onlyinclude>

== Troubleshooting ==
If installation fails, check the logs.

Now {{Installation Guide}} includes only the "Quick Start" section. The overview and troubleshooting sections are excluded.

Template Documentation Best Practices

Every template should include documentation so others know how to use it. Use <noinclude> to add docs without affecting transclusion:

<noinclude>
= Template:Infobox Product =

== Usage ==
<pre>
{{Infobox Product
|name=Product Name
|version=1.0
|status=Stable
|description=A brief description of the product.
}}
</pre>

== Parameters ==
; name: Product name (required)
; version: Current version (required)
; status: Release status (default: Stable)
; description: Short description (optional)
</noinclude>

<includeonly>
{| class="wikitable" style="float:right;width:300px;"
|+ {{{name}}}
|-
! Version || {{{version}}}
|-
! Status || {{{status|Stable}}}
|-
! Description || {{{description|}}}
|}
</includeonly>

This standard format includes:

• A usage example with all parameters
• Parameter descriptions with required/optional status
• Default values where applicable

Transclusion and Substitution

Normal transclusion updates automatically when the source changes. Substitution copies the content permanently.

{{TemplateName}}        Transclusion — updates with source
{{subst:TemplateName}}  Substitution — copies content, no future updates

Use subst: when:

• You want a permanent snapshot of the template output
• The template will be deleted but you want existing usages to keep working
• Performance is critical and you want to avoid template Parsing overhead

Once substituted, the page contains the literal output of the template and has no further connection to it.

What You Learned

• Transclusion includes content by reference, not by copying
• <noinclude> excludes content from transclusion
• <includeonly> shows content only during transclusion
• <onlyinclude> limits transclusion to specific content
• Parameters make templates dynamic with default values
• Template documentation belongs inside <noinclude>
• Substitution copies content permanently

In the next lesson, you'll learn about parser functions — MediaWiki's built-in programming language for conditional logic, calculations, and string manipulation.

Common Mistakes

Mistake	Why It Happens	How to Fix
Template content appears on the including page with raw {{{1}}} displayed	Missing parameter value	Provide the parameter value or add a default. {{{1\|}}} shows nothing if not provided. {{{1\|N/A}}} shows N/A.
<noinclude> content appears on the target page	Tag is closed incorrectly	Ensure <noinclude> and </noinclude> are on their own lines. The tags must be properly nested and closed.
Template shows nothing on the source page	All content is inside <includeonly>	This is intentional behavior. The template page appears empty because all display content is wrapped in <includeonly>. Add documentation outside the tags.
Transcluded content does not update	Page cache	Append ?action=purge to the including page URL to force a cache refresh. Template changes do not automatically purge pages that use them.
{{subst:...}} shows raw code instead of rendered output	Syntax error	Check that the template exists and is spelled correctly. subst: applies to the rendered template output, not the source code.

Practice Questions

1. What is the difference between <noinclude> and <includeonly>? Give a use case for each.
2. Create a template called "Status" that accepts a status parameter and displays a green "Online" or red "Offline" message based on the value.
3. How would you create a template that transcludes content from another page but only shows the first three sections?
4. Challenge: Build a complete "Staff Directory" system. Create a template called StaffMember with parameters for name, role, department, email, and photo. The template should render a formatted card. Then create 3 staff member pages that use the template with different data. Create a "Staff Directory" page that transcludes all three. Finally, add a category tag inside <includeonly> so the staff directory page is automatically categorized.

FAQ

What is the difference between a template and transclusion?

A template is a page in the Template namespace designed specifically for reuse. Transclusion is the mechanism of including any page into another. While templates are the most common use of transclusion, you can transclude any page by writing {{Namespace:PageName}}, even non-template pages.

Can I transclude a section from a page instead of the whole page?

Yes. Use tags around the section you want to include. Only content within is transcluded. For more precise section control, install Extension:Labeled Section Transclusion, which allows named sections.

What happens if I edit a template while pages are using it?

The change takes effect immediately on all pages that use the template. There is no staging or version control for templates. Always test changes on a sandbox copy first (e.g., Template:MyTemplate/Sandbox).

Can transclusion cause infinite loops?

Yes. If Template A includes Template B and Template B includes Template A, MediaWiki detects the loop and shows an error message. The page renders with a 'Template loop detected' error at the point of inclusion.

How do I create a template that works both as a transclusion and as a standalone page?

Use for content that should only appear during transclusion, and for content that should only appear on the template page itself. Content outside both tags appears in both contexts, which lets you create a page that serves double duty.

Mini Project

Goal: Build a reusable "Alert Box" template system with three severity levels.

1. Create Template:Alert with a type parameter (info, warning, error) and a message parameter
2. Use {{#switch:...}} or CSS to style each type differently:
   • Info: blue background
   • Warning: yellow background
   • Error: red background
3. Add <noinclude> documentation showing usage examples
4. Add a category inside <includeonly> that categorizes pages using the template
5. Create three test pages, each using the template with a different severity type
6. Verify that categorizing works — all three test pages appear in the category
7. Change the template style and verify all three pages update automatically

What's Next

Templates with parameters are powerful, but they become truly intelligent when combined with parser functions.

Continue to Lesson 14: Parser Functions — learn how to add conditional logic, switch statements, calculations, and date formatting to your templates.