|Uniform Type Identifier (UTI)||
|Developed by||John Gruber|
|Initial release||March 19, 2004|
(December 17, 2004)
|Type of format||Markup language|
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. 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.
John Gruber created the Markdown language in 2004, with significant collaboration with Aaron Swartz on the syntax, 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)”.
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, 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.
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.
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.
Sites such as GitHub, reddit, Diaspora, Stack Exchange, OpenStreetMap, and SourceForge use variants of Markdown to facilitate discussion between users. A Markdown dialect is also used by the instant messaging system Slack.
There is no clearly defined Markdown standard, apart from the original writeup and implementation by John Gruber, which some consider to be abandonware. 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. 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". 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.
A tool (named Babelmark2) 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". Gruber has argued that complete standardisation would be mistaken: "Different sites (and people) have different needs. No one syntax would make all happy."
A standards effort for the Internet media type
text/markdown (independent of the syntax) is underway in the IETF. The Internet-Draft, draft-ietf-appsawg-text-markdown, is planned to be submitted to the IESG in April 2015. The Markdown community is invited to submit use cases for Markdown, which will inform the media type standardization process.
A number of other lightweight markup languages extend Markdown by implementing added features (such as tables, footnotes, definition lists, and Markdown inside HTML blocks) not available with plain Markdown syntax. Among these are Markdown Extra, MultiMarkdown, and the Pandoc Markdown extension. In some cases, this is in order to enable conversion into more formats than HTML, e.g. LaTeX, RTF, and DocBook.
Many implementations also intentionally omit support for middle word emphasis. The original Markdown implementation interprets constructs like
my_long_variable as a request to emphasize "long" in the middle of a word. Many users found this confusing, so many later implementations such as PHP Markdown and Python Markdown do not implement middle word emphasis by default.
The essay "Thoughts on Markdown" stated that Markdown's original developer, John Gruber, has not responded to discussions about extensions to Markdown, and that "Markdown is changing, with or without him".
|text using Markdown syntax||the corresponding HTML produced by a Markdown processor||the text viewed in a browser|
<h1>Heading</h1> <h2>Sub-heading</h2> <h3>Another deeper heading</h3> <p>Paragraphs are separated by a blank line.</p> <p>Leave 2 spaces at the end of a line to do a<br /> line break</p> <p>Text attributes <em>italic</em>, <strong>bold</strong>, <code>monospace</code>, <s>strikethrough</s>.</p> <p>A <a href="http://example.com">link</a>.</p> <p>Shopping 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>The rain—not the reign—in Spain.</p>
Paragraphs are separated by a blank line.
Leave 2 spaces at the end of a line to do a
Text attributes italic, bold,
The rain—not the reign—in Spain.
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. There are a variety of such editors available for all major platforms. There are syntax highlighting plugins for Markdown built into emacs, gedit, and vim.
Implementations of Markdown are available for many different frameworks, platforms and languages.
- The sourcecode documentation generator Doxygen supports Markdown with extra features.
- RStudio, an IDE for R provides a C++ wrapper function for the markdown implementation sundown.
- IntelliJ IDEA, an IDE for Java, provides a Markdown plugin
- MultiMarkdown, a format and program with more syntax features and export options than traditional Markdown
- PageDown, a parser for StackExchange's Markdown syntax
- GitHub Flavored Markdown (GFM) adds syntax highlighting, task lists, and tables. 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
- "Parsedown" (Emanuil Rusev) - PHP
- Pandoc adds tables, line blocks, definition lists, superscripts and subscripts, can generate table of contents.
- Discount - a C implementation.
- Md2doc - a XSLT 2.0 implementation.
- Visual Studio Web Essentials - an extension library for Microsoft Visual Studio with live markdown preview
- Markdown Text Editor
- Markdown Test Suite
There are many more open-source implementations of Markdown available online.
- Similar lightweight markup languages:
- Comparison of document markup languages
- Comparison of documentation generators
- Daring Fireball Statement by creator John Gruber
- "Markdown". Aaron Swartz: The Weblog. March 19, 2004.
- "Daring Fireball: Markdown". Archived from the original on 2004-04-02. Retrieved April 25, 2014.
- Markdown 1.0.1 readme source code "Daring Fireball – Markdown". 17 Dec 2004.
- "Markdown: License". Daring Fireball. Retrieved April 25, 2014.
- "Markdown". December 4, 2013.
- Markdown Syntax "Daring Fireball – Markdown – Syntax". 13 Jun 2013.
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.
- "MarsEdit 2.3 ties the knot with Tumblr support – Ars Technica". Retrieved 2009-08-11.
- "Review: Practical Django Projects – Ars Technica". Retrieved 2009-08-11.
- "GitHub Flavored Markdown". github.com. Retrieved 29 March 2013.
- "Reddit markdown primer. Or, how do you do all that fancy formatting in your comments, anyway?". reddit.com. Retrieved 29 March 2013.
- "Markdown Editing Help". http://stackoverflow.com. Retrieved 11 April 2014.
- "SourceForge: Markdown Syntax Guide". sourceforge.net. Retrieved 2013-05-10.
- Atwood, Jeff. "Responsible Open Source Code Parenting". Codinghorror.com. Retrieved 2014-04-25.
- "Trouble with parentheses in Markdown hyperlinks". Six.pairlist.net. 2012-10-17. Retrieved 2014-04-25.
- Atwood, Jeff (2012-10-25). "The Future of Markdown". Codinghorror.com. Retrieved 2014-04-25.
- "Markdown Community Page". Markdown.github.io. Retrieved 2014-04-25.
- "Standard Markdown is now Common Markdown". Jeff Atwood. Retrieved 7 October 2014.
- "Standard Markdown Becomes Common Markdown then CommonMark". InfoQ. Retrieved 7 October 2014.
- "Babelmark 2 - Compare markdown implementations". Johnmacfarlane.net. Retrieved 2014-04-25.
- "Babelmark 2 - FAQ". Johnmacfarlane.net. Retrieved 2014-04-25.
- Gruber, John. "Twitter post". Retrieved 6 September 2014.
- "Pandoc Markdown". Pandoc. Retrieved 7 October 2014.
- "Markdown Discuss". Markdown-Discuss. Retrieved 7 October 2014.
- "Thoughts on Markdown - All this". www.leancrew.com. Retrieved 2015-05-06.
- No space between ] and (
- "Doxygen Manual: Markdown support". Stack.nl. 2014-04-21. Retrieved 2014-04-25.
- 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.
- "JetBrains Plugin Repository :: Markdown". Plugins.jetbrains.com. Retrieved 2014-04-25.
- "nicoulaj/idea-markdown Âˇ GitHub". Github.com. 2013-12-01. Retrieved 2014-04-25.
- "Writing on GitHub". help.github.com. Github, Inc. Retrieved 9 July 2014.
- "Pandoc's markdown". Retrieved 2014-08-05.
- "Discount - a C implementation of the Markdown markup language". Retrieved 2014-11-01.
- "Md2doc - Markdown2Html2Docbook XSLT 2.0 conversion tool". Retrieved 2014-11-25.