List of All the File Extensions Formats and Types Starting With the Letter M
| File Extension | Description |
| .M3U | MP3 songs playlist |
| .MA1 | Diablo II Act 1 saved map progress |
| .MA1.MMF | SMAF Synthetic music mobile application format |
| .MA2.MMF | SMAF Synthetic music mobile application format |
| .MACP | Apple Macintosh MacPaint bitmap image |
| .MACS | Apple Mac OS system |
| .MAF | Microsoft Access form shortcut |
| .MAILLOC | Apple Mac OS X Finder mail internet location |
| .MAILTOLOC | Apple Mail mail address |
| .MD | Chaos Desktop metadata Machine description Markdown markup language Mayura Draw vector drawing MDCD compressed files archive Moneydance financial data Mungyodance data pack MuseData music notation Technics keyboard user MIDI settings Teknical eLearning objects meta-data |
| .MKV | Matroska video-audio multimedia |
| .MP3 | Compressed audio and music file, mp3 songs or ringtones Masterpoint green points mp3HD audio mp3PRO SHARP MZ-series emulator |
| .MP4 | MPEG-4 video files format |
| .MPP | Microsoft Project plan files BX-24 Basic Express compiler map CAD drawing Musepack audio |
| .MUI | Amiga MUI default class/library MultiLanguage Windows resource Opengl Glut |