Markdown
Plain text markup language From Wikipedia, the free encyclopedia
Markdown[9] is a lightweight markup language for creating formatted text using a plain-text editor. John Gruber created Markdown in 2004 as an easy-to-read markup language.[9] Markdown is widely used for blogging and instant messaging, and also used elsewhere in online forums, collaborative software, documentation pages, and readme files.
| |
| Filename extensions | |
|---|---|
| Internet media type | text/markdown[2] |
| Uniform Type Identifier (UTI) | net.daringfireball.markdown |
| Developed by | |
| Initial release | March 9, 2004[3][4] |
| Latest release | |
| Type of format | Open file format[6] |
| Extended to | pandoc, MultiMarkdown, Markdown Extra, CommonMark,[7] RMarkdown[8] |
| Website | daringfireball |
The initial description of Markdown[10] contained ambiguities and raised unanswered questions, causing implementations to both intentionally and accidentally diverge from the original version. This was addressed in 2014 when long-standing Markdown contributors released CommonMark, an unambiguous specification and test suite for Markdown.[11]
History
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Markdown was inspired by pre-existing conventions for marking up plain text in email and usenet posts,[12] such as the earlier markup languages setext (c. 1992), Textile (c. 2002), and reStructuredText (c. 2002).[9]
In 2002 Aaron Swartz created atx and referred to it as "the true structured text format". Gruber created the Markdown language in 2004 with Swartz as his "sounding board".[13] The goal of the language was to enable people "to write using an easy-to-read and easy-to-write plain text format, optionally convert it to structurally valid XHTML (or HTML)".[5]
Another key design goal was readability, that the language be readable as-is, without looking like it has been marked up with tags or formatting instructions,[9] unlike text formatted with "heavier" markup languages, such as Rich Text Format (RTF), HTML, or even wikitext (each of which have obvious in-line tags and formatting instructions which can make the text more difficult for humans to read).
Gruber wrote a Perl script, Markdown.pl, which converts marked-up text input to valid, well-formed XHTML or HTML, encoding angle brackets (<, >) and ampersands (&), which would be misinterpreted as special characters in those languages. It can take the role of a standalone script, a plugin for Blosxom or a Movable Type, or of a text filter for BBEdit.[5]
Rise and divergence
As Markdown's popularity grew rapidly, many Markdown implementations appeared, driven mostly by the need for additional features such as tables, footnotes, definition lists,[note 1] and Markdown inside HTML blocks.
The behavior of some of these diverged from the reference implementation, as Markdown was only characterised by an informal specification[16] and a Perl implementation for conversion to HTML.
At the same time, a number of ambiguities in the informal specification had attracted attention.[17] These issues spurred the creation of tools such as Babelmark[18][19] to compare the output of various implementations,[20] and an effort by some developers of Markdown parsers for standardisation. However, Gruber has argued that complete standardization would be a mistake: "Different sites (and people) have different needs. No one syntax would make all happy."[21]
Gruber avoided using curly braces in Markdown to unofficially reserve them for implementation-specific extensions.[22]
Standardization
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| |
| Filename extensions | .md, .markdown[2] |
|---|---|
| Internet media type | text/markdown; variant=CommonMark[7] |
| Uniform Type Identifier (UTI) | uncertain[23] |
| UTI conformation | public.plain-text |
| Developed by | John MacFarlane, open source |
| Initial release | October 25, 2014 |
| Latest release | |
| Type of format | Open file format |
| Extended from | Markdown |
| Extended to | GitHub Flavored Markdown |
| Website | commonmark |
From 2012, a group of people, including Jeff Atwood and John MacFarlane, launched what Atwood characterised as a standardisation effort.[11]
A community website now aims to "document various tools and resources available to document authors and developers, as well as implementors of the various Markdown implementations".[25]
In September 2014, Gruber objected to the usage of "Markdown" in the name of this effort and it was rebranded as CommonMark.[12][26][27] CommonMark.org published several versions of a specification, reference implementation, test suite, and "[plans] to announce a finalized 1.0 spec and test suite in 2019".[28]
No 1.0 spec has since been released, as major issues still remain unsolved.[29]
Nonetheless, the following websites and projects have adopted CommonMark: Discourse, GitHub, GitLab, Reddit, Qt, Stack Exchange (Stack Overflow), and Swift.
In March 2016, two relevant informational Internet RFCs were published:
Variants
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Websites like Bitbucket, Diaspora, Discord,[31] GitHub,[32] OpenStreetMap, Reddit,[33] SourceForge[34] and Stack Exchange[35] use variants of Markdown to make discussions between users easier.
Depending on implementation, basic inline HTML tags may be supported.[36]
Italic text may be implemented by _underscores_ or *single-asterisks*.[37]
GitHub Flavored Markdown
GitHub had been using its own variant of Markdown since as early as 2009,[38] which added support for additional formatting such as tables and nesting block content inside list elements, as well as GitHub-specific features such as auto-linking references to commits, issues, usernames, etc.
In 2017, GitHub released a formal specification of its GitHub Flavored Markdown (GFM) that is based on CommonMark.[32] It is a strict superset of CommonMark, following its specification exactly except for tables, strikethrough, autolinks and task lists, which GFM adds as extensions.[39]
Accordingly, GitHub also changed the parser used on their sites, which required that some documents be changed. For instance, GFM now requires that the hash symbol that creates a heading be separated from the heading text by a space character.
Markdown Extra
Markdown Extra is a lightweight markup language based on Markdown implemented in PHP (originally), Python and Ruby.[40] It adds the following features that are not available with regular Markdown:
- Markdown markup inside HTML blocks
- Elements with id/class attribute
- "Fenced code blocks" that span multiple lines of code
- Tables[41]
- Definition lists
- Footnotes
- Abbreviations
Markdown Extra is supported in some content management systems such as Drupal,[42] Grav (CMS) and TYPO3.[43]
Examples
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| Text using Markdown syntax | Corresponding HTML produced by a Markdown processor | Text viewed in a browser |
|---|---|---|
Heading
=======
Sub-heading
-----------
# Alternative heading
## Alternative sub-heading
Paragraphs are separated
by a blank line.
Two spaces at the end of a line
produce a line break.
|
<h1>Heading</h1>
<h2>Sub-heading</h2>
<h1>Alternative heading</h1>
<h2>Alternative sub-heading</h2>
<p>Paragraphs are separated
by a blank line.</p>
<p>Two spaces at the end of a line<br />
produce a line break.</p>
|
Paragraphs are separated by a blank line. Two spaces at the end of a line |
Text attributes _italic_, **bold**, `monospace`.
Horizontal rule:
---
|
<p>Text attributes <em>italic</em>, <strong>bold</strong>, <code>monospace</code>.</p>
<p>Horizontal rule:</p>
<hr />
|
Text attributes italic, bold, monospace.
Horizontal rule: |
Bullet lists nested within numbered list:
1. fruits
* apple
* banana
2. vegetables
- carrot
- broccoli
|
<p>Bullet lists nested within numbered list:</p>
<ol>
<li>fruits <ul>
<li>apple</li>
<li>banana</li>
</ul></li>
<li>vegetables <ul>
<li>carrot</li>
<li>broccoli</li>
</ul></li>
</ol>
|
Bullet lists nested within numbered list:
|
A [link](http://example.com).
> Markdown uses email-style
characters for blockquoting.
>
> Multiple paragraphs need to be prepended individually.
Most inline <abbr title="Hypertext Markup Language">HTML</abbr> tags are supported.
|
<p>A <a href="http://example.com">link</a>.</p>
<p><img alt="Image" title="icon" src="Icon-pictures.png" /></p>
{{blockquote|
<p>Markdown uses email-style characters for blockquoting.</p>
<p>Multiple paragraphs need to be prepended individually.</p>
}}
<p>Most inline <abbr title="Hypertext Markup Language">HTML</abbr> tags are supported.</p>
|
A link.
Most inline HTML tags are supported. |
Implementations
Implementations of Markdown are available for over a dozen programming languages; in addition, many applications, platforms and frameworks support Markdown.[44] For example, Markdown plugins exist for every major blogging platform.[12]
While Markdown is a minimal markup language and is read and edited with a normal text editor, there are specially designed editors that preview the files with styles, which are available for all major platforms. Many general-purpose text and code editors have syntax highlighting plugins for Markdown built into them or available as optional download. Editors may feature a side-by-side preview window or render the code directly in a WYSIWYG fashion.
See also
Explanatory notes
- Technically HTML description lists
References
External links
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