|Internet media type|
|Uniform Type Identifier (UTI)|
|Developed by||John Gruber (in collaboration with Aaron Swartz on the syntax)|
|Initial release||March 19, 2004|
(December 17, 2004)
|Type of format||Markup language|
|Extended to||MultiMarkdown, Markdown Extra, CommonMark, RMarkdown|
Markdown is a lightweight markup language with plain text formatting syntax. Its design allows it to be converted to many output formats, but the original tool by the same name only supports HTML. 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.
Since the initial description of Markdown contained ambiguities and unanswered questions, the implementations that appeared over the years have subtle differences and many come with syntax extensions.
John Gruber created the Markdown language in 2004 in collaboration with Aaron Swartz on the syntax, with the goal of enabling people "to write using an easy-to-read and easy-to-write plain text format, optionally convert it to structurally valid XHTML (or HTML)".
Its 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, Textile, and reStructuredText.
Gruber wrote a Perl script,
Markdown.pl, which converts marked-up text input to valid, well-formed XHTML or HTML and replaces 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 e.g. in 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.
Markdown has been characterised by an informal specification and a reference implementation for conversion to HTML. Over time, many Markdown implementations have appeared. People developed these mostly driven by the need for additional features on top of the base syntax—such as tables, footnotes, definition lists (technically HTML description lists), and Markdown inside HTML blocks. The behavior of some of these diverges from the reference implementation. At the same time, a number of ambiguities in the informal specification have attracted attention. These issues spurred an effort by some developers of Markdown parsers for standardisation.
Babelmark  is a tool 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 standardization would be mistaken: "Different sites (and people) have different needs. No one syntax would make all happy."
In March 2016 RFC 7763 and RFC 7764 were published. RFC 7763 introduced MIME type
text/markdown with the original variant. RFC 7764 discusses and registered the variants MultiMarkdown, GitHub Flavored Markdown (GFM), Pandoc, CommonMark, and Markdown Extra among others.
|Internet media type|
|Uniform Type Identifier (UTI)||uncertain|
|Developed by||John MacFarlane, open source|
|Initial release||October 25, 2014|
(April 6, 2019)
|Type of format||Markup language|
|Extended to||GitHub Flavored Markdown|
From 2012, a group of people including Jeff Atwood and John MacFarlane 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. CommonMark.org published several versions of a specification, reference implementation, and test suite, and "[plans] to announce a finalized 1.0 spec and test suite in 2019."
GitHub Flavored Markdown (GFM)
In 2017, GitHub released a formal specification of their GitHub Flavored Markdown (GFM) that is based on CommonMark. It follows the CommonMark specification exactly except for tables, strikethrough, autolinks and task lists, which the GitHub spec has added as extensions. GitHub also changed the parser used on their sites accordingly, 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 is a lightweight markup language based on Markdown implemented in PHP (originally), Python and Ruby. It adds features not available with plain Markdown syntax. Markdown Extra is supported in content management systems, for example Drupal, TYPO3 and MediaWiki.
It adds the following features to Markdown:
- markdown markup inside HTML blocks
- elements with id/class attribute
- fenced code blocks
- tables 
- definition lists
|Text using Markdown syntax||Corresponding HTML produced by a Markdown processor||Text viewed in a browser|
Heading ======= Sub-heading ----------- Paragraphs are separated by a blank line. Two spaces at the end of a line produces a line break. Text attributes _italic_, **bold**, `monospace`. Horizontal rule: --- Strikethrough: ~~strikethrough~~ Bullet list: * apples * oranges * pears Numbered list: 1. lather 2. rinse 3. repeat An [example](http://example.com). ![Image](Icon-pictures.png "icon") > Markdown uses email-style > characters for blockquoting. Inline <abbr title="Hypertext Markup Language">HTML</abbr> is supported.
<h1>Heading</h1> <h2>Sub-heading</h2> <p>Paragraphs are separated by a blank line.</p> <p>Two spaces at the end of a line<br /> produces a line break.</p> <p>Text attributes <em>italic</em>, <strong>bold</strong>, <code>monospace</code>.</p> <p>Horizontal rule:</p> <hr /> <p>Strikethrough:</p> <strike>strikethrough</strike> <p>Bullet list:</p> <ul> <li>apples</li> <li>oranges</li> <li>pears</li> </ul> <p>Numbered list:</p> <ol> <li>lather</li> <li>rinse</li> <li>repeat</li> </ol> <p>An <a href="http://example.com">example</a>.</p> <p><img alt="Image" title="icon" src="Icon-pictures.png" /></p> <blockquote> <p>Markdown uses email-style > characters for blockquoting.</p> </blockquote> <p>Inline <abbr title="Hypertext Markup Language">HTML</abbr> is supported.</p>
Paragraphs are separated by a blank line.
Two spaces at the end of a line
Text attributes italic,
Inline HTML is supported.
Implementations of Markdown are available for over a dozen programming languages; in addition, many platforms and frameworks support Markdown. For example, Markdown plugins exist for every major blogging platform.
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.
- The sourcecode documentation generator Doxygen supports Markdown with extra features.
- RStudio, an IDE for R, provides a C++ wrapper function for a markdown variant called sundown.
- GitHub Flavored Markdown (GFM) ignores underscores in words, and adds syntax highlighting, task lists, and tables.
- Discount – a C implementation.
- MarkAPL is a converter written in Dyalog APL. It supports fenced blocks, smart typography, link references, and special attributes, and can generate a table of contents.
- PHP Markdown - a library package that includes the PHP Markdown parser and its sibling PHP Markdown Extra with additional features.
- Markdig – A .NET library that follows the CommonMark specifications, and includes a collection of extensions and the ability for the user to create their own.
- Comparison of document markup languages
- Comparison of documentation generators
- Lightweight markup language
- Wiki markup
- RFC 7763 - The text/markdown Media Type
- Swartz, Aaron (2004-03-19). "Markdown". Aaron Swartz: The Weblog.
- Gruber, John. "Daring Fireball: Markdown". Daring Fireball. Archived from the original on 2004-04-02. Retrieved 2014-04-25.
- Markdown 1.0.1 readme source code "Daring Fireball – Markdown". 2004-12-17. Archived from the original on 2004-04-02.
- RFC7764 – Guidance on Markdown: Design Philosophies, Stability Strategies, and Select Registrations
- RMarkdown Reference site - RMarkdown Reference site
- "Markdown: License". Daring Fireball. Retrieved 2014-04-25.
- Daring Fireball statement by creator John Gruber
- "Markdown". 2013-12-04. Archived from the original on 2004-04-02.
- 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.
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- Gruber, John [@gruber] (4 September 2014). "@tobie @espadrine @comex @wycats Because different sites (and people) have different needs. No one syntax would make all happy" (Tweet) – via Twitter.
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- "UTI of a CommonMark document".
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- "CommonMark". 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.
- "GitHub Flavored Markdown Spec".
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- Official website for original John Gruber markup