Markdown

Markdown^[11] 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.^[11] Markdown is widely used for blogging, instant messaging, and large language models,^[12] and also used elsewhere in online forums, collaborative software, documentation pages, and readme files.

The initial description of Markdown^[13] 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.^{[14][better source needed]}

History

Markdown was inspired by pre-existing conventions for marking up plain text in email and usenet posts,^[15] such as the earlier markup languages setext (c. 1992), Textile (c. 2002), and reStructuredText (c. 2002).^[11]

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".^[16] 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, 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 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]

CommonMark

Standardization

In 2012, a group of people, including Jeff Atwood and John MacFarlane, launched what Atwood characterised as a standardization effort.^[14]

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".^[24]

Name

In September 2014, Gruber objected to the usage of "Markdown" in the name of this effort and it was rebranded as "CommonMark".^[15][25][26] 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".^[27] A finalized 1.0 spec has not been released, as major issues still remain unsolved.^[28]

Adoption

Nonetheless, several websites and projects have adopted CommonMark, including Codeberg, Discourse, GitHub, GitLab, Reddit, Qt, Stack Exchange (Stack Overflow), and Swift.

In March 2016, two relevant informational Internet RFCs were published:

Variants

Websites like Bitbucket, Diaspora, Discord,^[29] GitHub,^[30] OpenStreetMap, Reddit,^[31] SourceForge^[32] and Stack Exchange^[33] use variants of Markdown to make discussions between users easier.

Depending on implementation, basic inline HTML tags may be supported.^[34]

Italic text may be implemented by _underscores_ or *single-asterisks*.^[35]

GitHub Flavored Markdown

GitHub had been using its own variant of Markdown since as early as 2009,^[36] 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.^[30] It is a strict superset of CommonMark, following its specification exactly except for tables, strikethrough, autolinks and task lists, which GFM adds as extensions.^[37]

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.^[38] 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^[39]
• Definition lists
• Footnotes
• Abbreviations

Markdown Extra is supported in some content management systems such as Drupal,^[40] Grav (CMS), Textpattern CMS^[41] and TYPO3.^[42]

Examples

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>

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 />

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>

A [link](http://example.com).

![Image](Icon-pictures.png "icon")

> 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>

Implementations

Implementations of Markdown are available for over a dozen programming languages; in addition, many applications, platforms and frameworks support Markdown.^[43] For example, Markdown plugins exist for every major blogging platform.^[15]

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

• Comparison of document markup languages
• Comparison of documentation generators
• Comparison of wiki software
• Lightweight markup language
• List of markup languages
• List of text editors
• Wiki markup

Explanatory notes

1. ^ Technically HTML description lists

References

1. ^ Gruber, John (8 January 2014). "The Markdown File Extension". The Daring Fireball Company, LLC. Archived 12 July 2020 at the Wayback Machine. Retrieved 27 March 2022. Too late now, I suppose, but the only file extension I would endorse is ".markdown", for the same reason offered by Hilton Lipschitz: We no longer live in a 8.3 world, so we should be using the most descriptive file extensions. It's sad that all our operating systems rely on this stupid convention instead of the better creator code or a metadata model, but great that they now support longer file extensions.
2. ^ rfc7763
3. ^ Swartz, Aaron (2004-03-19). "Markdown". Aaron Swartz: The Weblog. Archived 2017-12-24 at the Wayback Machine. Retrieved 2013-09-01.
4. ^ Gruber, John. "Markdown". Daring Fireball. Archived 2004-03-11 at the Wayback Machine. Retrieved 2022-08-20.
5. ^ Markdown 1.0.1 readme source code "Daring Fireball – Markdown". 2004-12-17. Archived from the original on 2004-04-02.
6. ^ "RMarkdown Reference site". Archived 2020-03-03 at the Wayback Machine. Retrieved 2019-11-21.
7. ^ "Markdown: License". Daring Fireball. Archived 2020-02-18 at the Wayback Machine. Retrieved 2014-04-25.
8. ^ rfc7764
9. ^ "UTI of a CommonMark document". 12 April 2017. Archived 22 November 2018 at the Wayback Machine. Retrieved 29 September 2017.
10. ^ "CommonMark specification". Archived 2017-08-07 at the Wayback Machine. Retrieved 2017-07-26.
11. ^ philosophy
12. ^ Dillet, Romain (6 March 2025). "Mistral adds a new API that turns any PDF document into an AI-ready Markdown file". TechCrunch. Retrieved 7 September 2025.
13. ^ "Daring Fireball: Introducing Markdown". daringfireball.net. Archived 2020-09-20 at the Wayback Machine. Retrieved 2020-09-23.
14. ^ Atwood, Jeff (2012-10-25). "The Future of Markdown". CodingHorror.com. Archived from the original on 2014-02-11. Retrieved 2014-04-25.
15. ^ Gilbertson, Scott (October 5, 2014). "Markdown throwdown: What happens when FOSS software gets corporate backing?". Ars Technica. Archived November 14, 2020 at the Wayback Machine. Retrieved June 14, 2017. CommonMark fork could end up better for users... but original creators seem to disagree.
16. ^ "I should write about it, but it's painful. More or less: Aaron was my sounding board, my muse.". No. 741989829173510145.
17. ^ "Markdown Syntax Documentation". Daring Fireball. Archived 2019-09-09 at the Wayback Machine. Retrieved 2018-03-09.
18. ^ "GitHub Flavored Markdown Spec – Why is a spec needed?". github.github.com. Archived 2020-02-03 at the Wayback Machine. Retrieved 2018-05-17.
19. ^ "Babelmark 2 – Compare markdown implementations". Johnmacfarlane.net. Archived 2017-07-18 at the Wayback Machine. Retrieved 2014-04-25.
20. ^ "Babelmark 3 – Compare Markdown Implementations". github.io. Archived 2020-11-12 at the Wayback Machine. Retrieved 2017-12-10.
21. ^ "Babelmark 2 – FAQ". Johnmacfarlane.net. Archived 2017-07-28 at the Wayback Machine. Retrieved 2014-04-25.
22. ^ Gruber, John (4 September 2014). "@tobie @espadrine @comex @wycats Because different sites (and people) have different needs. No one syntax would make all happy.". No. 507670720886091776.
23. ^ Gruber, John (19 May 2022). "Markdoc". Daring Fireball. Archived 19 May 2022 at the Wayback Machine. Retrieved May 19, 2022. I love their syntax extensions — very true to the spirit of Markdown. They use curly braces for their extensions; I'm not sure I ever made this clear, publicly, but I avoided using curly braces in Markdown itself — even though they are very tempting characters — to unofficially reserve them for implementation-specific extensions. Markdoc's extensive use of curly braces for its syntax is exactly the sort of thing I was thinking about.
24. ^ "Markdown Community Page". GitHub. Archived 2020-10-26 at the Wayback Machine. Retrieved 2014-04-25.
25. ^ "Standard Markdown is now Common Markdown". Jeff Atwood. 4 September 2014. Archived 2014-10-09 at the Wayback Machine. Retrieved 2014-10-07.
26. ^ "Standard Markdown Becomes Common Markdown then CommonMark". InfoQ. Archived 2020-09-30 at the Wayback Machine. Retrieved 2014-10-07.
27. ^ "CommonMark". Archived 12 April 2016 at the Wayback Machine. Retrieved 20 Jun 2018. The current version of the CommonMark spec is complete, and quite robust after a year of public feedback … but not quite final. With your help, we plan to announce a finalized 1.0 spec and test suite in 2019.
28. ^ "Issues we MUST resolve before 1.0 release [6 remaining]". CommonMark Discussion. 2015-07-26. Archived 2021-04-14 at the Wayback Machine. Retrieved 2020-10-02.
29. ^ "Markdown Text 101 (Chat Formatting: Bold, Italic, Underline)". Discord. 2024-10-03. Retrieved 2025-02-07.
30. ^ "GitHub Flavored Markdown Spec". GitHub. Archived 2020-02-03 at the Wayback Machine. Retrieved 2020-06-11.
31. ^ "Reddit markdown primer. Or, how do you do all that fancy formatting in your comments, anyway?". Reddit. Archived 2019-06-11 at the Wayback Machine. Retrieved 2013-03-29.
32. ^ "SourceForge: Markdown Syntax Guide". SourceForge. Archived 2019-06-13 at the Wayback Machine. Retrieved 2013-05-10.
33. ^ "Markdown Editing Help". StackOverflow.com. Archived 2014-03-28 at the Wayback Machine. Retrieved 2014-04-11.
34. ^ "Markdown Syntax Documentation". daringfireball.net. Archived 2019-09-09 at the Wayback Machine. Retrieved 2021-03-01.
35. ^ "Basic Syntax: Italic". The Markdown Guide. Matt Cone. Archived 26 March 2022 at the Wayback Machine. Retrieved 27 March 2022. To italicize text, add one asterisk or underscore before and after a word or phrase. To italicize the middle of a word for emphasis, add one asterisk without spaces around the letters.
36. ^ Tom Preston-Werner. "GitHub Flavored Markdown Examples". GitHub. Archived 2021-05-13 at the Wayback Machine. Retrieved 2021-04-02.
37. ^ "A formal spec for GitHub Flavored Markdown". GitHub Engineering. 14 March 2017. Archived 3 February 2020 at the Wayback Machine. Retrieved 16 Mar 2017.
38. ^ Fortin, Michel (2018). "PHP Markdown Extra". Michel Fortin website. Archived 2021-01-17 at the Wayback Machine. Retrieved 2018-12-26.
39. ^ "PHP Markdown Extra". Michel Fortin. Archived 2021-01-17 at the Wayback Machine. Retrieved 2018-12-26.
40. ^ "Markdown editor for BUEditor". 4 December 2008. Archived 17 September 2020 at the Wayback Machine. Retrieved 15 January 2017.
41. ^ "Plugin: wet_textfilter_markdown". Textpattern CMS plugins. 2025-04-27.
42. ^ "Markdown for TYPO3 (markdown_content)". extensions.typo3.org. Archived 2021-02-01 at the Wayback Machine. Retrieved 2019-02-06.
43. ^ "W3C Community Page of Markdown Implementations". W3C Markdown Wiki. Archived 17 September 2020 at the Wayback Machine. Retrieved 24 March 2016.

External links

• Official website for original John Gruber markup