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

The initial description of Markdown[10] contained ambiguities and raised unanswered questions, causing implementations to both intentionally and accidentally diverge from the original version.

[11] 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).

[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)".

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.

[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.

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

[37] 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.

[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.