| Abbreviation | Definition |
|---|---|
| M2A | MPEG-2 audio Sound |
| M2V | MPEG-2 IPB videostream Video |
| M3 | Modula3 language source code file |
| M3A | Sound (MPEG-3 audio) |
| M3D | 3d animation macro (Corel Motion) |
| M3U | MPEG URL Sound reference file |
| M4 | M4 preprocessor file (unix) |
| M4U | File extension for an MPEG-4 Playlist file. |
| M7 | Sound (Farallon's MacRecorder format) (sampling rate 7k) |
| MA | Mathematica notebook ASCII file |
| MA | MicroApp HDC products for MicroApp executable files |
| MA3 | Harvard Graphics 3.0 Macro |
| MAC | Apple Macintosh Black & White MacPaint file Bitmap graphics |
| MAC | Macro |
| MACP | Apple Macintosh Black & White MacPaint file Bitmap graphics |
| MAD | MicroSoft Access module Shortcut |
| MAF | MS Access Form shortcut |
| MAG | Woody Lynn's MAG graphics format (MPS Magro Paint System) |
| MAH | Mahjongg Solitaire Settings file |
| MAI | Mail message |