Markdown is a lightweight markup language for creating formatted text using a plain-text editor. John Gruber and Aaron Swartz created Markdown in 2004 as a markup language that is appealing to human readers in its source code form. Markdown is widely used in blogging, instant messaging, online forums, collaborative software, documentation pages, and readme files.
|Internet media type|
|Uniform Type Identifier (UTI)|
|Developed by||John Gruber and Aaron Swartz|
|Initial release||March 19, 2004|
December 17, 2004
|Type of format||Open file format|
|Extended to||pandoc, MultiMarkdown, Markdown Extra, CommonMark, RMarkdown|
The initial description of Markdown 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.
Markdown was inspired by pre-existing conventions for marking up plain text in email and usenet posts, such as the earlier markup languages setext (c. 1992), Textile (c. 2002), and reStructuredText (c. 2002).
In 2002 Aaron Swartz created atx and referred to it as “the true structured text format”. Swartz and Gruber then worked together to create the Markdown language in 2004, 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 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).
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 take the role of a standalone script, a plugin for Blosxom or a Movable Type, or of a text filter for BBEdit.
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.
The behavior of some of these diverged from the reference implementation, as Markdown was only characterised by an informal specification and a Perl implementation for conversion to HTML.
At the same time, a number of ambiguities in the informal specification had attracted attention. These issues spurred the creation of tools such as Babelmark to compare the output of various implementations, and an effort by some developers of Markdown parsers for standardisation. 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."
Gruber avoided using curly braces in Markdown to unofficially reserve them for implementation-specific extensions.
|Internet media type|
|Uniform Type Identifier (UTI)||uncertain|
|Developed by||John MacFarlane, open source|
|Initial release||October 25, 2014|
June 19, 2021
|Type of format||Open file format|
|Extended to||GitHub Flavored Markdown|
From 2012, a group of people, including Jeff Atwood and John MacFarlane, launched what Atwood characterised as a standardisation 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 CommonMark. 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." No 1.0 spec has since been released as major issues still remain unsolved. Nonetheless, the following websites and projects have adopted CommonMark: Discourse, GitHub, GitLab, Reddit, Qt, Stack Exchange (Stack Overflow), and Swift.
In March 2016 two relevant informational Internet RFCs were published:
Websites like GitHub, Bitbucket, Reddit, Diaspora, Stack Exchange, OpenStreetMap and SourceForge use variants of Markdown to facilitate discussion between users. Markdown is also supported in a wide variety of apps and services, like Microsoft Teams chat and Discord messages.
GitHub had been using its own variant of Markdown since as early as 2009, adding 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. It is a strict superset of CommonMark, following its specification exactly except for tables, strikethrough, autolinks and task lists, which GFM adds 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 some content management systems such as, for example, Drupal and TYPO3.
Markdown Extra adds the following features to Markdown:
|Text using Markdown syntax||Corresponding HTML produced by a Markdown processor||Text viewed in a browser|
Heading ======= Sub-heading ----------- # Alternative 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> <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, |
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). ![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>
Most inline HTML tags are 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.
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.
This document registers the text/markdown media type for use with Markdown, a family of plain-text formatting syntaxes that optionally can be converted to formal markup languages such as HTML.
This document elaborates upon the text/markdown media type for use with Markdown, a family of plain-text formatting syntaxes that optionally can be converted to formal markup languages such as HTML. Background information, local storage strategies, and additional syntax registrations are supplied.
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.
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.
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.