Markdown markup language
File type: Miscellaneous file
Files with the mdml file extension contain source text written in the Markdown markup language.
Markdown uses simple punctuation and text conventions to provide formatting that remains readable in its unprocessed form.
File type category:
Miscellaneous file
Date updated: November 4, 2026
Markdown was created by John Gruber and Aaron Swartz to provide maximum readability and "publishability" in both its input and output forms. It takes many cues from conventions used to mark up plain text in email. Markdown converts marked-up text to valid, well-formed XHTML; left-pointing angle brackets and ampersands are replaced with their corresponding character entity references.
The original Markdown implementation was written in Perl by Gruber. Other developers have since reimplemented Markdown in a variety of programming languages. It is distributed under a BSD-style license and is included with, or available as a plug-in for, several content-management systems. The Markdown language remains in use, although specific implementations may produce HTML or other output instead of XHTML.
An mdml file is plain text and can be opened in any text editor. To read its formatted content, open it with a Markdown processor or an application that supports Markdown rendering.
A Markdown processor can render an mdml file as HTML or XHTML. This converts the marked-up source into a formatted document; saving the result as plain text preserves the original Markdown source rather than creating a different format.
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