| m2r | Micromuse Mib2Rules Data |
| m2s | Maxthon 2 Browser Skin |
| m2u | Maxthon 2 Browser Layout Data |
| m3 | Juki AMS Embroidery Data |
| m3c | IBM Voice Type Languages Newuser Data |
| m3d | DIALux 3D Model Data |
| m3d | DJ Mix Pro Database |
| m3i | IBM Voice Type Languages Newuser Data |
| m3r | Autodesk Moldflow 3D Fill+Pack Restart File |
| m3x | MAGIX Digital Foto Maker PhotoCD Playlist Data |
| m4c | IBM Voice Type Languages Newuser Data |
| m4d | Sage MAS 90 Data File |
| m4i | IBM Voice Type Languages Newuser Data |
| m4p | Sage MAS 90 Program File |
| m4t | Sage MAS 90 Table File |
| m5p | MachFive Preset Data |
| m64 | Mupen64 Movie Capture |
| m6b | Speedtronic Mark VI Data |
| m77t | GEODAS MGD77T Data |
| m7a | MapKing Map Data |
| m7c | Yamaha M7CL Digital Mixing Console Data |
| m98 | Nokia Mediamaster 9800S Satellites Data |
| m99 | MicroStation Modification User Resource File |
| maa | MMANA Antenna Data |
| mab | Mozilla Address Book |
| mac | Minitab Macro Data |
| mac | PATCHMASTER Macro File |
| mac | SmartWare Macro File |
| macbin | Macbinary Encoded |
| macro | Tecplot 360 Macro Data |
| macs | MADRIX Encrypted Script |
| mad | Microsoft Access Module Shortcut |
| mads | Metadata Authority Description Schema Data |
| magiwol | MagiWOL Data |
| mai | Pegasus Mail Sub Directory |
