An MKD file is a text file created using one of several possible dialects of the Markdown language. It is saved in plain text format but includes inline text symbols that define how to format the text (e.g., bold, indentations, headers, table formatting). MKD files may also be saved as .MD, .MARKDOWN, or .MDOWN files

MKD file are used to author plain text documentation that can be easily converted to HTML. However, they are not only useful for HTML documentation systems, but also for source code version control. MKD files can be compared against historical revisions in human-readable text, whereas a binary format cannot be easily compared.