Markdown Extra is a lightweight markup language based on Markdown implemented in PHP (originally), Python and Ruby. For instance, GFM now requires that the hash symbol that creates a heading be separated from the heading text by a space character. GitHub also changed the parser used on their sites accordingly, which required that some documents be changed. It is a strict superset of CommonMark, following its specification exactly except for tables, strikethrough, autolinks and task lists, which GFM adds as extensions. In 2017, GitHub released a formal specification of its GitHub Flavored Markdown (GFM) that is based on CommonMark. 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. Italic text may be implemented by _underscores_ and/or *single-asterisks*. ĭepending on implementation, basic inline HTML tags may be supported. Markdown is also supported in a wide variety of apps and services, like Microsoft Teams chat and Discord messages.
Websites like GitHub, Bitbucket, Reddit, Diaspora, Stack Exchange, OpenStreetMap and SourceForge use variants of Markdown to facilitate discussion between users. RFC 7764 discussed and registered the variants MultiMarkdown, GitHub Flavored Markdown (GFM), Pandoc, and Markdown Extra among others.RFC 7763 introduced MIME type text/markdown.In March 2016 two relevant informational Internet RFCs were published:
Nonetheless, the following websites and projects have adopted CommonMark: Discourse, GitHub, GitLab, Reddit, Qt, Stack Exchange ( Stack Overflow), and Swift. published several versions of a specification, reference implementation, test suite, and " 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. In September 2014, Gruber objected to the usage of "Markdown" in the name of this effort and it was rebranded as CommonMark. 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". Standardization CommonMarkįrom 2012, a group of people, including Jeff Atwood and John MacFarlane, launched what Atwood characterised as a standardisation effort. Gruber avoided using curly braces in Markdown to unofficially reserve them for implementation-specific extensions. However, Gruber has argued that complete standardization would be a mistake: "Different sites (and people) have different needs. 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. 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.Īt the same time, a number of ambiguities in the informal specification had attracted attention. Rise and divergence Īs Markdown's popularity grew rapidly, many Markdown implementations appeared, driven mostly by the need for additional features such as tables, footnotes, definition lists, and Markdown inside HTML blocks. It can take the role of a standalone script, a plugin for Blosxom or a Movable Type, or of a text filter for BBEdit. Gruber wrote a Perl script,, 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. 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).
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)." In 2002 Aaron Swartz created atx and referred to it as “the true structured text format”. 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.
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