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Markdown
Plain text markup language From Wikipedia, the free encyclopedia
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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 and instant messaging, and also used elsewhere in online forums, collaborative software, documentation pages, and readme files.
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The initial description of Markdown[10] 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.[11]
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History
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Markdown was inspired by pre-existing conventions for marking up plain text in email and usenet posts,[12] 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".[13] 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).
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]
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Rise and divergence
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[16] and a Perl implementation for conversion to HTML.
At the same time, a number of ambiguities in the informal specification had attracted attention.[17] These issues spurred the creation of tools such as Babelmark[18][19] to compare the output of various implementations,[20] 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."[21]
Gruber avoided using curly braces in Markdown to unofficially reserve them for implementation-specific extensions.[22]
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Standardization
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From 2012, a group of people, including Jeff Atwood and John MacFarlane, launched what Atwood characterised as a standardisation effort.[11]
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".[25]
In September 2014, Gruber objected to the usage of "Markdown" in the name of this effort and it was rebranded as CommonMark.[12][26][27] 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".[28]
No 1.0 spec has since been released, as major issues still remain unsolved.[29]
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:
Variants
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Websites like Bitbucket, Diaspora, Discord,[31] GitHub,[32] OpenStreetMap, Reddit,[33] SourceForge[34] and Stack Exchange[35] use variants of Markdown to make discussions between users easier.
Depending on implementation, basic inline HTML tags may be supported.[36]
Italic text may be implemented by _underscores_ or *single-asterisks*.[37]
GitHub Flavored Markdown
GitHub had been using its own variant of Markdown since as early as 2009,[38] 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.[32] It is a strict superset of CommonMark, following its specification exactly except for tables, strikethrough, autolinks and task lists, which GFM adds as extensions.[39]
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
Markdown Extra is a lightweight markup language based on Markdown implemented in PHP (originally), Python and Ruby.[40] 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[41]
- Definition lists
- Footnotes
- Abbreviations
Markdown Extra is supported in some content management systems such as Drupal,[42] Grav (CMS) and TYPO3.[43]
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Examples
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Implementations
Implementations of Markdown are available for over a dozen programming languages; in addition, many applications, platforms and frameworks support Markdown.[44] For example, Markdown plugins exist for every major blogging platform.[12]
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.
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See also
Explanatory notes
- Technically HTML description lists
References
External links
Wikiwand - on
Seamless Wikipedia browsing. On steroids.
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