| m14 | Microsoft Money 2005 Backup Data |
| m15 | Microsoft Money 2006 Backup Data |
| m16 | Microsoft Money 2007 Backup Data |
| m2d | SNMP v2c MIB Data |
| m2d | HTC Manila 2D Skin |
| m2f | Maxthon 2 Browser Filter |
| m2l | Maxthon 2 Language Pack |
| m2p | Maxthon 2 Browser Plugin |
| m2p | GROMACS Mat2PS Data |
| m2s | Maxthon 2 Browser Skin |
| m3d | DJ Mix Pro Database |
| m3r | Autodesk Moldflow 3D Fill+Pack Restart File |
| 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 |
| m64 | Mupen64 Movie Capture |
| m77t | GEODAS MGD77T Data |
| m7a | MapKing Map Data |
| m7c | Yamaha M7CL Digital Mixing Console Data |
| m99 | MicroStation Modification User Resource File |
| maa | MMANA Antenna Data |
| mab | Mozilla Address Book |
| mac | PATCHMASTER Macro File |
| mac | SmartWare Macro File |
| macbin | Macbinary Encoded |
| mad | Microsoft Access Module Shortcut |
| mail | NeoPlanet Mail Data |
| main | FileMaker Pro Dictionary Data |
| maj | CAMduct Job Data |
| mamp | MAMP Related Data |
| map | Map Data |
| map | TECkit Mapping Table |
| map | WAsP Terrain Map |
| maplet | Maple Maplet File |