Markdown

Markdown

Filename extensions	.md, .markdown[1][2]
Internet media type	text/markdown[2]
Uniform Type Identifier (UTI)	net.daringfireball.markdown
Developed by	John Gruber
Initial release	March 19, 2004[3][4]
Latest release	1.0.1 (December 17, 2004[5])
Type of format	Markup language
Extended to	MultiMarkdown, Markdown Extra, CommonMark[6]
Open format?	yes[7]
Website	daringfireball.net/projects/markdown/

Markdown is a lightweight markup language with plain text formatting syntax designed so that it can be converted to HTML and many other formats using a tool by the same name.^[8][9] Markdown is often used to format readme files, for writing messages in online discussion forums, and to create rich text using a plain text editor.

History

John Gruber created the Markdown language in 2004, with significant collaboration from Aaron Swartz on the syntax,^[3][4] with the goal of enabling people "to write using an easy-to-read, easy-to-write plain text format, and optionally convert it to structurally valid XHTML (or HTML)”.^[5]

The key design goal is readability – that the language be readable as-is, without looking like it has been marked up with tags or formatting instructions,^[10] unlike text formatted with a markup language, such as Rich Text Format (RTF) or HTML, which have obvious tags and formatting instructions. To this end, its main inspiration is the existing conventions for marking up plain text in email, though it also draws from earlier markup languages, notably setext, atx (by Aaron Swartz), Textile, reStructuredText, Grutatext, and EtText.^[10]

Gruber wrote a Perl script, Markdown.pl, which converts marked-up text input to valid, well-formed XHTML or HTML and replaces left-pointing angle brackets ('<') and ampersands with their corresponding character entity references. It can be used as a standalone script, as a plugin for Blosxom or Movable Type, or as a text filter for BBEdit.^[5]

Markdown has since been re-implemented by others as a Perl module available on CPAN (Text::Markdown), and in a variety of other programming languages. It is distributed under a BSD-style license and is included with, or available as a plugin for, several content-management systems.^[7][11][12]

Sites such as GitHub, reddit, Diaspora, Stack Exchange, OpenStreetMap, and SourceForge use variants of Markdown to facilitate discussion between users.^{[13][14][15][16]} A Markdown dialect is also used by the instant messaging system Slack.^[17]

Standardization

There is no clearly defined Markdown standard, apart from the original writeup and implementation by John Gruber, which some consider abandonware.^[18][19] This has led to fragmentation as different vendors write their own variants of the language to correct flaws or add missing features.

From 2012 through 2014, a group of people including Jeff Atwood launched what Atwood characterized as a standardization effort.^[20] 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".^[21] In September 2014, Gruber objected to the usage of "Markdown" in the name of this effort and it was rebranded as a new dialect named CommonMark.^[22][23]

A tool (named Babelmark2^[24]) is also available to "[compare] the output of various implementations" to "promote discussion of how and whether certain vague aspects of the markdown spec should be clarified".^[25] Gruber has argued that complete standardisation would be mistaken: "Different sites (and people) have different needs. No one syntax would make all happy."^[26]

A standards effort for the Internet media type text/markdown (independent of the syntax) is underway in the IETF. An Internet-Draft, draft-ietf-appsawg-text-markdown,^[2] has been submitted to the IESG in April 2015. The Markdown community is invited to submit use cases for Markdown to inform the media type standardization process.

Extensions

A number of other lightweight markup languages extend Markdown by adding features (such as tables, footnotes, definition lists, and Markdown inside HTML blocks) not available in plain Markdown syntax. Among these are Markdown Extra, MultiMarkdown, and the Pandoc Markdown extension.^[27] In some cases, this is to enable conversion into more formats than just HTML, e.g., LaTeX, RTF, and DocBook.

The original Markdown implementation interprets constructs like my_long_variable as a request to emphasize "long". Many users found this confusing, so many later implementations such as PHP Markdown and Python Markdown do not implement middle word emphasis with underscores.^[28]

Example

Text using Markdown syntax	Corresponding HTML produced by a Markdown processor	Text viewed in a browser
Heading ======= Sub-heading ----------- ### A deeper heading Horizontal rule line. Paragraphs are separated by a blank line. Two spaces at the end of a line leave a line break. Text attributes _italic_, *italic*, __bold__, **bold**, `monospace`. Bullet list: * apples * oranges * pears Numbered list: 1. apples 2. oranges 3. pears A [link](http://example.com).	<h1>Heading</h1> <h2>Sub-heading</h2> <h3>Another deeper heading</h3> <hr>Horizontal rule line <p>Paragraphs are separated by a blank line.</p> <p>Two spaces at the end of a line leave a<br /> line break.</p> <p>Text attributes <em>italic</em>, <em>italic</em>, <strong>bold</strong>, <strong>bold</strong>, <code>monospace</code>.</p> <p>Bullet list:</p> <ul> <li>apples</li> <li>oranges</li> <li>pears</li> </ul> <p>Numbered list:</p> <ol> <li>apples</li> <li>oranges</li> <li>pears</li> </ol> <p>A <a href="http://example.com">link</a>.</p>	Heading Sub-heading Another deeper heading Paragraphs are separated by a blank line. Two spaces at the end of a line leave a line break. Text attributes italic, italic, bold, bold, monospace. Bullet list: apples oranges pears Numbered list: apples oranges pears A link.

Implementations

Implementations of Markdown are available for over a dozen programming languages; in addition, many platforms and frameworks support Markdown.^[29] For example, Markdown plugins exist for every major blogging platform.^[30]

While Markdown is a minimal markup language and is easily 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 try to render the code directly in a WYSIWYG-like fashion.

• The sourcecode documentation generator Doxygen supports Markdown with extra features.^[31]
• RStudio, an IDE for R provides a C++ wrapper function for a markdown variant called sundown.^[32]
• IntelliJ IDEA, an IDE for Java, provides a Markdown plugin^[33][34]
• MultiMarkdown, a format and program with more syntax features and export options than traditional Markdown
• PageDown, a parser for StackExchange's Markdown syntax^[35], written in JavaScript, based on Showdown by John Fraser
• GitHub Flavored Markdown (GFM) treats newlines in paragraph-like content as real line breaks, ignores underscores in words, and adds syntax highlighting, task lists,^[36] and tables.^[37] It has several implementations:
  • "Grip - GitHub Readme Instant Preview" (Joe Esposito) - Python
  • "Vim-Flavored-Markdown" (Jeff Tratner) - Vim scripting
  • "GitHub-Flavored Markdown Comments" (Evan Solomon) - PHP WordPress plugin
  • "Markdown on Save" (Mark Jaquith) - PHP WordPress plugin
  • "Node-GFM" (Gabriel Llamas) - JavaScript
  • "Parsedown" (Emanuil Rusev) - PHP
• Pandoc adds tables, line blocks, definition lists, superscripts and subscripts, can generate table of contents.^[38]
• Discount - a C implementation.^[39]
• Md2doc - a XSLT 2.0 implementation.^[40]
• Visual Studio Web Essentials - an extension library for Microsoft Visual Studio with live markdown preview
• Markdown editing and live preview in Linux with a python module^[41]
• MarkAPL is a converter written in Dyalog APL. It supports fenced blocks, smart typography, link references, special attributes and can generate a table of contents.^[42]
• PHP Markdown - a library package that includes the PHP Markdown parser and its sibling PHP Markdown Extra with additional features.^[43]

See also

• Similar lightweight markup languages:
  • AsciiDoc, supports many document types
  • Org-mode
  • txt2tags
  • Wiki markup
• Comparison of document markup languages
• Comparison of documentation generators

References

1. Daring Fireball Statement by creator John Gruber
2. RFC 7763 - The text/markdown Media Type
3. "Markdown". Aaron Swartz: The Weblog. 2004-03-19.
4. "Daring Fireball: Markdown". Archived from the original on 2004-04-02. Retrieved 2014-04-25.
5. Markdown 1.0.1 readme source code "Daring Fireball – Markdown". 2004-12-17.
6. RFC7764 – Guidance on Markdown: Design Philosophies, Stability Strategies, and Select Registrations
7. "Markdown: License". Daring Fireball. Retrieved 2014-04-25.
8. "Markdown". 2013-12-04.
9. http://johnmacfarlane.net/pandoc/index.html
10. Markdown Syntax "Daring Fireball – Markdown – Syntax". 2013-06-13. Readability, however, is emphasized above all else. A Markdown-formatted document should be publishable as-is, as plain text, without looking like it’s been marked up with tags or formatting instructions. While Markdown’s syntax has been influenced by several existing text-to-HTML filters — including Setext, atx, Textile, reStructuredText, Grutatext, and EtText — the single biggest source of inspiration for Markdown’s syntax is the format of plain text email.
11. "MarsEdit 2.3 ties the knot with Tumblr support – Ars Technica". Retrieved 2009-08-11.
12. "Review: Practical Django Projects – Ars Technica". Retrieved 2009-08-11.
13. "GitHub Flavored Markdown". Github.com. Retrieved 2013-03-29.
14. "Reddit markdown primer. Or, how do you do all that fancy formatting in your comments, anyway?". Reddit.com. Retrieved 2013-03-29.
15. "Markdown Editing Help". StackOverflow.com. Retrieved 2014-04-11.
16. "SourceForge: Markdown Syntax Guide". SourceForge.net. Retrieved 2013-05-10.
17. . Slack.com https://api.slack.com/docs/formatting. Missing or empty |title= (help)
18. Atwood, Jeff. "Responsible Open Source Code Parenting". Codinghorror.com. Retrieved 2014-04-25.
19. "Trouble with parentheses in Markdown hyperlinks". Six.pairlist.net. 2012-10-17. Retrieved 2014-04-25.
20. Atwood, Jeff (2012-10-25). "The Future of Markdown". CodingHorror.com. Retrieved 2014-04-25.
21. "Markdown Community Page". Github. Retrieved 2014-04-25.
22. "Standard Markdown is now Common Markdown". Jeff Atwood. Retrieved 2014-10-07.
23. "Standard Markdown Becomes Common Markdown then CommonMark". InfoQ. Retrieved 2014-10-07.
24. "Babelmark 2 - Compare markdown implementations". Johnmacfarlane.net. Retrieved 2014-04-25.
25. "Babelmark 2 - FAQ". Johnmacfarlane.net. Retrieved 2014-04-25.
26. Gruber, John. "Twitter post". Retrieved 2014-09-06.
27. "Pandoc Markdown". Pandoc. Retrieved 2014-10-07.
28. "Markdown Discuss". Markdown-Discuss. Retrieved 2014-10-07.
29. "W3C Community Page of Markdown Implementations". W3C Markdown Wiki. Retrieved 24 March 2016.
30. "Markdown THrowdown – What happens when FOSS software gets corporate backing". Ars Technica. 2014-10-00. Check date values in: |date= (help)
31. "Doxygen Manual: Markdown support". Stack.nl. 2014-04-21. Retrieved 2014-04-25.
32. file 462 lines (396 sloc) 12.572 kb. "rstudio/src/cpp/core/markdown/Markdown.cpp at master · rstudio/rstudio · GitHub". Github.com. Retrieved 2014-04-25.
33. "JetBrains Plugin Repository :: Markdown". Plugins.jetbrains.com. Retrieved 2014-04-25.
34. "nicoulaj/idea-markdown ¡ GitHub". Github.com. 2013-12-01. Retrieved 2014-04-25.
35. Atwood, Jeff (2012-10-25). "The Future of Markdown". Codinghorror.com. Retrieved 2014-04-25.
36. "Writing on GitHub". help.github.com. Github, Inc. Retrieved 9 July 2014.
37. "GitHub Flavored Markdown". github.com. Retrieved 29 March 2013.
38. "Pandoc's markdown". Retrieved 2014-08-05.
39. "Discount - a C implementation of the Markdown markup language". Retrieved 2014-11-01.
40. "Md2doc - Markdown2Html2Docbook XSLT 2.0 conversion tool". Retrieved 2014-11-25.
41. "Markdown editing and live preview with three simple tools.".
42. "Markdown converter written in Dyalog APL.".
43. "PHP Markdown". Retrieved 2016-03-01.

External links

• Official website at daringfireball.net