Markdown

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MarkdownFilename extensions.md, .markdown[1][2]Internet media typetext/markdown[2]Uniform Type Identifier (UTI)net.daringfireball.markdownUTI conformationpublic.plain-textMagic numberNoneDeveloped byInitial releaseMarch 9, 2004 (21 years ago) (2004-03-09)[3][4]Latest releaseType of formatOpen file format[6]Extended topandoc, MultiMarkdown, Markdown Extra, CommonMark,[7] RMarkdown[8]Websitedaringfireball.net/projects/markdown/

Markdown[9] 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.[9] Markdown is widely used for blogging, instant messaging, and large language models,[10] and also used elsewhere in online forums, collaborative software, documentation pages, and readme files.

The initial description of Markdown[11] 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.[12][better source needed]

Markdown was inspired by pre-existing conventions for marking up plain text in email and usenet posts,[13] such as the earlier markup languages setext (c. 1992), Textile (c. 2002), and reStructuredText (c. 2002).[9]

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”.[14] 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,[9] 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 a Movable Type, or of a text filter for BBEdit.[5]

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 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.”[22]

Gruber avoided using curly braces in Markdown to unofficially reserve them for implementation-specific extensions.[23]

CommonMarkFilename extensions.md, .markdown[2]Internet media typetext/markdown; variant=CommonMark[7]Uniform Type Identifier (UTI)uncertain[24]UTI conformationpublic.plain-textDeveloped byJohn MacFarlane, open sourceInitial releaseOctober 25, 2014 (11 years ago) (2014-10-25)Latest releaseType of formatOpen file formatExtended fromMarkdownExtended toGitHub Flavored MarkdownWebsitecommonmark.org spec.commonmark.org

In 2012, a group of people, including Jeff Atwood and John MacFarlane, launched what Atwood characterised as a standardisation effort.[12]

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”.[26]

In September 2014, Gruber objected to the usage of “Markdown” in the name of this effort and it was rebranded as “CommonMark”.[13][27][28] 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”.[29]

No 1.0 spec has since been released, as major issues still remain unsolved.[30]

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

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

RFC 7763 introduced MIME type text/markdown.
RFC 7764 discussed and registered the variants MultiMarkdown, GitHub Flavored Markdown (GFM), Pandoc, and Markdown Extra among others.[31]

Websites like Bitbucket, Diaspora, Discord,[32] GitHub,[33] OpenStreetMap, Reddit,[34] SourceForge[35] and Stack Exchange[36] use variants of Markdown to make discussions between users easier.

Depending on implementation, basic inline HTML tags may be supported.[37]

Italic text may be implemented by _underscores_ or *single-asterisks*.[38]

GitHub had been using its own variant of Markdown since as early as 2009,[39] 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.[33] It is a strict superset of CommonMark, following its specification exactly except for tables, strikethrough, autolinks and task lists, which GFM adds as extensions.[40]

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 is a lightweight markup language based on Markdown implemented in PHP (originally), Python and Ruby.[41] 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[42]
Definition lists
Footnotes
Abbreviations

Markdown Extra is supported in some content management systems such as Drupal,[43] Grav (CMS), Textpattern CMS[44] and TYPO3.[45]

Text using Markdown syntax Corresponding HTML produced by a Markdown processor Text viewed in a browser

Paragraphs are separated by a blank line.

Two spaces at the end of a line produce a line break.

Text attributes italic, bold, monospace.

Horizontal rule:

Bullet lists nested within numbered list:

fruits
- apple
- banana
vegetables
- carrot
- broccoli

A link.

Markdown uses email-style characters for blockquoting.

Multiple paragraphs need to be prepended individually.

Most inline HTML tags are supported.

Implementations of Markdown are available for over a dozen programming languages; in addition, many applications, platforms and frameworks support Markdown.[46] For example, Markdown plugins exist for every major blogging platform.[13]

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.