Help:ParserFunctions

Shortcuts

ParserFunctions are features of MediaWiki that allow editors to perform conditional logic, mathematical expressions, string handling, and time/date formatting within wikitext. They are implemented as magic words beginning with a hash mark (e.g., ), and are provided by the ParserFunctions extension and the core parser.

Syntax overview

General form: {{#functionname: param1 | param2 | ... }}
Pipes (|) separate parameters.
Nested functions are allowed; parse from the innermost to outermost.
Whitespace around pipes is usually ignored, but avoid trailing spaces in titles or file names.

Core functions

{{[[Template:#if|#if]]}} – conditional presence: then; Renders then if test is non-empty; otherwise renders else.; Example: No parameter

{{[[Template:#ifeq|#ifeq]]}} – equality test: not equal; Compares normalized strings (case-sensitive by default).

{{[[Template:#iferror|#iferror]]}} – catch parser errors: ok; True if expression produces a parser error (e.g., division by zero).

{{[[Template:#ifexpr|#ifexpr]]}} – numeric condition: Expression error: Unrecognized punctuation character "'".; Evaluates arithmetic/boolean expressions (see #expr).

{{[[Template:#switch|#switch]]}} – multi-branch selection: outputD; First matching case wins; use #default for fallback.

{{[[Template:#time|#time]]}} – format dates and times: Error: Invalid time.; Example: 2026-04-10 → outputs current date.

{{[[Template:#expr|#expr]]}} – arithmetic and comparisons: Expression error: Unrecognized punctuation character "'".; Supports + - * / ^ parentheses, comparisons (= < > <= >= <>), logical and or not, and functions like round, floor, ceil, mod.; Example: 20 → 20

{{[[Template:#language|#language]]}} – language names: code → language name for ISO code (e.g., 日本語 → Japanese).

String functions (from Scribunto or templates)

MediaWiki core has limited string handling. Many projects use Scribunto (Lua) or helper templates to emulate:

text / TEXT – lowercase/uppercase
Text / text – change first letter case
value, ...
Template:Len: text – length (often via template)

Check local documentation for which helpers are installed.

Nesting and precedence

Nest ParserFunctions to build complex logic: yes
Use parentheses in #expr to control order: 9
Strip markers may appear with heavy nesting; preview to ensure expected output.

Examples

Conditional content: Welcome, Guest!

Switch-based messages: Status unknown

Dates: Fri, 10 Apr 2026 17:13:06 +0000 → RFC 2822 datetime; January 31, 2024 → January 31, 2024

Math: 81 → 81; correct

Localization: 中文 → Chinese

Common pitfalls

Use |- to separate table rows (not |--).
#expr is plain text; it does not render TeX. To typeset math, use $...$ .
Avoid trailing spaces in parameters; they can affect equality tests.
Division by zero triggers errors; catch with #iferror.
Excessive nesting may cause strip-marker artifacts; simplify or split logic.

Performance notes

Complex ParserFunctions increase parse time; prefer templates or Lua for heavy logic.
Caching: Output that varies by time or variables may reduce cache hits.