An MD 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). MD files are designed for authoring plain text documentation that can be easily converted to HTML.

MD file open in Microsoft Notepad MD files are not only useful for HTML documentation systems, but also for source code version control. This is because the files can be compared against historical revisions in human-readable text (whereas a binary format cannot be easily compared). Projects created with GitHub, a popular online version control system, often use a file named README.md, which contains the readme for the project. John Gruber, the developer of Markdown, has created a Perl program for converting Markdown to HTML. The program, called "Markdown," is available at the Daring Fireball website. NOTE: Markdown files also used the .MARKDOWN extension.

File or group of files compressed using MDCD compression

Data file saved by Moneydance, a personal finance software program similar to Intuit Quicken or Microsoft Money; stores bank accounts, transactions, budgets, stock portfolios, and other information.

Moneydance supports Mac, Windows, Linux, OS/2, Solaris, and Unix platforms.

Game ROM used by emulation software for the SEGA Mega Drive, an older game console (called the SEGA Genesis in North America); stores the contents of a game cartridge; used for running older games on the PC.

NOTE: SBWin can be used to convert MD files to the .BIN SEGA game ROM format, which can be played by many different SEGA Master Drive/Genesis emulators.

File created by Sharkport, a hardware accessory for the PlayStation 2; contains a PS2 saved game created by the Sharkport device; used for copying saved games to the PC and sharing them with other players; can be converted to other saved game formats, such as .PSU, using the PS2 Save Builder.

NOTE: Sharkport also now uses the .PS2 extension for saved games.