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, instant messaging, and large language models,[10] and also used elsewhere in online forums, collaborative software, documentation pages, and readme files.
.md, .markdown[1][2]text/markdown[2]net.daringfireball.markdownpublic.plain-text| Markdown | |
|---|---|
 | |
| Filename extensions | .md, .markdown[1][2] |
| Internet media type | text/markdown[2] |
| Uniform Type Identifier (UTI) | net.daringfireball.markdown |
| UTI conformation | public.plain-text |
| Magic number | None |
| 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[11] 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.[12][better source needed]
History
Markdown was inspired by pre-existing conventions for marking up plain text in email and usenet posts,[13] 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".[14] 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).[citation needed]
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.[citation needed]
The behavior of some of these diverged from the reference implementation, as Markdown was only characterised by an informal specification[17] and a Perl implementation for conversion to HTML.[citation needed]
At the same time, a number of ambiguities in the informal specification had attracted attention.[18] These issues spurred the creation of tools such as Babelmark[19][20] to compare the output of various implementations,[21] and an effort by some developers of Markdown parsers for standardization. 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."[22]
Gruber avoided using curly braces in Markdown to unofficially reserve them for implementation-specific extensions.[23]
Standardization
| CommonMark | |
|---|---|
| Filename extensions | .md, .markdown[2] |
| Internet media type | text/markdown; variant=CommonMark[7] |
| Uniform Type Identifier (UTI) | uncertain[24] |
| 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 |
In 2012, a group of people, including Jeff Atwood and John MacFarlane, launched what Atwood characterised as a standardization effort.[12]
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".[26]
In September 2014, Gruber objected to the usage of "Markdown" in the name of this effort and it was rebranded as "CommonMark".[13][27][28] 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".[29]
The finalized 1.0 spec has not been released, as major issues still remain unsolved.[30]
Nonetheless, the following websites and projects have adopted CommonMark: Codeberg, Discourse, GitHub, GitLab, Reddit, Qt, Stack Exchange (Stack Overflow), and Swift.
In March 2016, two relevant informational Internet RFCs were published:
- RFC 7763 – "The text/markdown Media Type,"[2] Informational. Introduces MIME type
text/markdown. - RFC 7764 – "Guidance on Markdown: Design Philosophies, Stability Strategies, and Select Registrations,"[7] Informational. Discusses and registers the variants MultiMarkdown, GitHub Flavored Markdown (GFM), Pandoc, and Markdown Extra (among others).[31]
Variants
Websites like Bitbucket, Diaspora, Discord,[32] GitHub,[33] OpenStreetMap, Reddit,[34] SourceForge[35] and Stack Exchange[36] use variants of Markdown to make discussions between users easier.
Depending on implementation, basic inline HTML tags may be supported.[37]
Italic text may be implemented by _underscores_ or *single-asterisks*.[38]
GitHub Flavored Markdown
GitHub had been using its own variant of Markdown since as early as 2009,[39] 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.[33] It is a strict superset of CommonMark, following its specification exactly except for tables, strikethrough, autolinks and task lists, which GFM adds as extensions.[40]
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.[41] 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[42]
- Definition lists
- Footnotes
- Abbreviations
Markdown Extra is supported in some content management systems such as Drupal,[43] Grav (CMS), Textpattern CMS[44] and TYPO3.[45]
Examples
| 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>
</blockquote>
<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.[46] For example, Markdown plugins exist for every major blogging platform.[13]
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