Lightweight markup language

A lightweight markup language is a markup language with a simple syntax, designed to be easy for a human to enter with a simple text editor, and easy to read in its raw form.

Lightweight markup languages are used in applications where people might be expected to read the document source as well as the rendered output. For instance, a person downloading a software library might prefer to read the documentation in a text editor rather than a browser.

Another application is for entry in web-based publishing, such as weblogs and wikis, where the input interface is a simple text box. The server software converts the input to a common document markup language like HTML or XHTML.

History

Lightweight markup languages were originally used on text-only displays which could not display characters in italics or bold, so informal methods to convey this information had to be developed. This formatting choice was naturally carried forth to plain-text email communications.

1986 international standard SGML provided facilities to define and parse lightweight markup languages using grammars and tag implication. The 1998 W3C XML is a profile of SGML that omits these facilities.

List of lightweight markup languages

The following is a partial list of lightweight markup languages.

Presentation oriented

• AsciiDoc
• BBCode
• Curl (programming language)
• Creole
• Crossmark
• Epytext
• EtText
• Haml
• JsonML
• MakeDoc
• Markdown
• POD
• reStructuredText
• Ruby Document format
• Setext
• SiSU
• SPIP
• Texy!
• Textile
• txt2tags
• UDO
• Wikitext

Data serialization oriented

• Curl (programming language) (homoiconic, but also reads JSON; every object serializes)
• JSON
• OGDL
• Simple Declarative Language
• YAML

Comparison of language features

Comparing language features

Language	Implementation language or platf.	HTML export tool	HTML import tool	Tables	Link titles	class attribute	id attribute	Exportable formats	License
BBCode	PHP, C#	No	No	No	No	No	No	HTML, XHTML	Public Domain
declarative Curl	?	?	?	Yes	Yes	?	?	Implement as macros, text formats, procedures in packages or as objects or anonymous functions	Commercial Curl Inc. and Sumisho
Creole	?	?	?	Yes	No	No	No	Depends on impl.	CC-by-SA 1.0
Markdown	PHP, C#, JavaScript	Yes	Yes	No	Yes	No	No	XHTML	BSD-style & GPL (both)
Markdown Extra	PHP, Ruby	Yes	Yes	Yes	Yes	No	No	XHTML	BSD-style & GPL (both)
MediaWiki	PHP	Yes	Yes	Yes	Yes	Yes	Yes	XHTML	GNU GPL
PmWiki	PHP	No	Yes	Yes	Yes	Yes	Yes	XHTML 1.0 Transitional	GNU GPL
POD	Perl	Yes	?	No	Yes	?	?	HTML, XHTML, XML, UNIX man, LaTeX, plain text, RTF, DocBook	Artistic License, Perl's license
reStructuredText	Python, Haskell, Java,	Yes	No	Yes	Yes	Yes	auto	Latex, XML, PseudoXML, HTML (w3c valid), PDF	Python License
Textile	PHP, Java, Perl, Python, Rubu, ASP, C#	Yes	No	Yes	Yes	Yes	Yes	XHTML	Textile License
Texy!	PHP, C#; Java in progress	Yes	Yes	Yes	Yes	Yes	Yes	XHTML or HTML	GNU GPL v2 License
txt2tags	Python	Yes	?	Yes	Yes	?	?	HTML, XHTML, SGML, LaTeX, Lout, UNIX man, Wikipedia, Google Code Wiki, DokuWiki, MoinMoin, MagicPoint, PageMaker	GPL

Comparison of lightweight markup language syntax

Text/font-face formatting

Comparing text formatting syntax

Language	Bold	Italic	Monospace (teletype)	Notes
AsciiDoc	*bold text*	_italic text_	+monospace text+	Can double operators to ignore special characters (for example **bold _text** yields bold _text).
BBCode	[b]bold text[/b]	[i]italic text[/i]	[code]monospace text[/code]	Formatting works across line breaks.
declarative Curl	{bold text}	{italic text}	{monospace text}	text formats accept options like any Curl Visual object
Creole	**bold text**	//italic text//	{{{monospace text}}}	Triple curly braces are for nowiki which is optionally monospace in Creole (the choice of the implementor). Future Creole additions may introduce double hash marks (##) for monospace.
Markdown	**bold text** or __bold text__	*italic text* or _italic text_	Non-monospace text     monospace text     more monospace text Inline `monospaced` text.	Markdown doesn't use bold and italic tags, but rather em (typically italic) and strong (typically bold) tags. Monospace text is created by indenting that line 4 spaces or one tab character, or enclosing text in backticks: `monospaces`.
MediaWiki	'''bold text'''	''italic text''	<code>monospace text</code>
PmWiki	'''bold text'''	''italic text''	@@monospace text@@
POD	B<bold text>	I<italic text>	C<monospace text>	Indented text is also shown as monospaced code.
reStructuredText	**bold text**	*italic text*	``monospace text``
Textile	*bold text* or **bold text**	_italic text_ or __italic text__	@monospace text@	Textile uses em (typically italic) and strong (typically bold) tags on single symbols (and code tag), and i and b tags on double symbols.
Texy!	**bold text**	*italic text* or //italic text//	`monospace text`	Texy uses by default em (typically italic) and strong (typically bold) tags. It is possible to configure library to use another tags.
txt2tags	**bold text**	//italic text//	``monospace text``

Section headers

Comparing section header formatting

Language	Format	Notes
AsciiDoc	= Level 1 Header == Level 2 Header == === Level 3 Header or Level 1 Header ============== Level 2 Header -------------- Level 3 Header ~~~~~~~~~~~~~~	Close equals signs are optional (ignored if present). Level 1 is document/page title.
BBCode		Does not support section headers
declarative Curl	{heading level=1 Header} {heading level=2 Header} {heading level=3 Header}	Usual options available for a Curl Visual obbject.
Creole	= Level 1 Header == Level 2 Header == === Level 3 Header	Close equals signs are optional (ignored if present).
Markdown	# Level 1 Header ## Level 2 Header or Level 1 Header ============== Level 2 Header --------------	You can optionally "close" the #-style headers with an equal number of #'s. The #-style headers support up to 6 levels. The = and - style headers support only the two shown.
MediaWiki	== Level 2 Header == === Level 3 Header ===	= is available for level 1 header, but its use is discouraged in Wikipedia (reserved for page title). More = are possible, up to 6.
PmWiki	!! Level 2 Header !!! Level 3 Header	! is available for level 1 header, but its use is discouraged in PmWiki (used for the page title). More ! are possible, up to 6.
POD	=head1 Level 1 heading =head2 Level 2 heading
reStructuredText	Chapter 1 Title =============== Section 1.1 Title ----------------- Subsection 1.1.1 Title ~~~~~~~~~~~~~~~~~~~~~~ Section 1.2 Title ----------------- Chapter 2 Title ===============	Any of the following characters can be used as the "underline": = - ` : ' " ~ ^ _ * + # < >. The same character must be used for the same indentation level and may not be used for a new indentation level.
Textile	h1. Level 1 Header h2. Level 2 Header	Up to 6 levels
Texy!	### Level 1 Header ## Level 2 Header or Level 1 Header ============== Level 2 Header --------------	You can optionally "close" the #-style headers with an equal number of #'s. The #-style headers support up to 6 levels. The underlined style headers support four levels (### *** === ----). Resulting absolute levels numbers are calculated dynamically. Optionally, less chars can denote higher header level.
txt2tags	= Level 1 Header = == Level 2 Header == === Level 3 Header ===	Up to 6 levels. Using + characters instead of = characters creates numbered headers (the default being unnumbered).

Link syntax

Comparing link syntax

Language	Syntax	Notes
AsciiDoc	http://www.example.com http://www.example.com][Link text]
BBCode	[url]http://www.example.com[/url] [url=http://www.example.com]Link text[/url]	Some BBCode implementations can auto-parse URLs as well and convert them to a elements.
declarative Curl	{link href={url "http://www.example.com"}, Link text} {link href={url "http://www.example.com"}, Link text}	An option is target="" Note that {url } is itself a Curl macro
Creole	[[Internal Page]] [[Internal Page|Display Text]] [[http://www.example.com|Link text]] [[WikiCreole:Creole1.0|InterWiki Link]]	Free standing URL's are also detected.
Markdown	[Link text](http://www.example.com "optional title attribute") or [Link text][id] and elsewhere [id]: http://www.example.com "optional title attribute"	Allows for an optional title attribute.
MediaWiki	[[Internal page]] [[Internal page|Displayed text]] [http://www.example.com] [http://www.example.com External link]	Wikitext can auto-parse URLs as well and convert them to a elements.
PmWiki	[[Internal page]] [[Internal page|Displayed text]] [[http://www.pmwiki.org]] [[http://www.Pmwiki.org|External link]]	Wikitext can auto-parse URLs without spaces in them as well and convert them to a elements.
POD	L</Internal Link> L<Perl::Module::Link> L<http://example.com/external_link>	The core POD standard does not support external links with titles.
reStructuredText	`Link text <http://www.example.com/>`_	Can also be done in a non-embedded format which may be seen as more readable.
Textile	"Link text (optional title attribute)":http://www.example.com or "Link text":alias and elsewhere [alias (optional title attribute)]http://www.example.com	Allows for an optional title attribute.
Texy!	"Link text .(optional title)[opt. class or ID]{opt. style}":http://www.example.com or "Link text":alias and elsewhere [alias]: http://www.example.com .(optional title)[opt. class or ID]{opt. style}	Texy! modifiers allows for an optional title attribute, CSS classes, ID, inline style and HTML element attributes. Example: "Link .(title)[class#id]{color: blue;rel:nofollow}"
txt2tags	[Link text www.example.com]	Txt2tags can auto-parse URLs as well and convert them to a elements. Also has support for targeting references within the same text, not just URLs.

See also

• Comparison of documentation generators

External links

• Interesting notes with many links
• C2's list
• Curl Markup to replace HTML+CSS+JS
• Inhabitants of the authoring ecosphere
• List at otl website
• A comparison
• Pandoc: a versatile inter-format converter
• wikibooks Curl