| m7c | Yamaha M7CL Digital Mixing Console Data |
| m99 | MicroStation Modification User Resource File |
| maa | MMANA Antenna Data |
| mab | Mozilla Address Book |
| mac | SmartWare Macro File |
| mac | PATCHMASTER Macro File |
| macbin | Macbinary Encoded |
| macro | Tecplot 360 Macro Data |
| mad | Microsoft Access Module Shortcut |
| mads | Metadata Authority Description Schema Data |
| mail | NeoPlanet Mail Data |
| mailtoloc | Mac OS X Finder Mail Internet Location |
| main | FileMaker Pro Dictionary Data |
| maj | CAMduct Job Data |
| mamc | Auto Mouse Click Script |
| mamp | MAMP Related Data |
| man | AquaCrop Field Management Data |
| map | WAsP Terrain Map |
| map | TECkit Mapping Table |
| map | Map Data |
| maplet | Maple Maplet File |
| mapx | MapDotNet UX Map File |
| marshal | Marshal Data Migration Model |
| mask | Adobe SpeedGrade Color Mask |
| mat | Kerkythea Material Data |
| material | Rigs of Rods Texture Reference |
| math | AnalyticMath Data |
| matl | Sonnet Substrate Data |
| matplot | Matplotlib Plot |
| mauve | Mauve Alignment Data |
| maxc | Autodesk 3D Studio MAX Container |
| maxd | PaperPort Annotation Data |
| maxfr | MaxView Web Pointer Data |
| mb1 | Math Blaster 1 Data |
| mb1 | UltraEdit Menus Data |