| mrk | Pro/ENGINEER Markup File |
| mrm | CloseToSoftware MacroRunner Macro |
| mrp | Xilinx MAP Report |
| mrpd | IBM TS3500 Machine Reported Product Data |
| mrq | NETFILE Tax Data |
| mrs | Corel WordPerfect Macro Resource |
| mrsl | THOR Metadata Rich Spectral Library Data |
| mrt | Stimulsoft Report |
| mrv | Marvin Document Format File |
| mrx | Malete Record Access File |
| mry | Mercury Binary Crystal Data |
| mryx | Mercury Compressed XML Crystal Data |
| ms | Autodesk 3D Studio Max Script |
| ms-tnef | MS Transport Neutral Encapsulation Format |
| ms1 | Crux MS/MS Data |
| ms2 | Crux MS/MS Data |
| ms2 | MADRIX Setup Data |
| ms4 | MAILERS+4 Index Data |
| msbcm | Microsoft Office Business Contact Manager Backup Data |
| msbt | Nintendo Wii Galaxy Dialogue Data |
| msc | CRiSP Harvest Maturation Rate Parameters Data |
| mscc | mSecure Data |
| mscg | Microsoft ClipArt Gallery for Mac Data |
| mscml | Media Server Control Markup Language File |
| mscx | mSecure Backup |
| msd | Map Service Definition |
| msd | Scream MiniSEED Data |
| msdl | Manchester Scene Description Language Data |
| mse-export-template | Magic Set Editor Export Template |
| mse-game | Magic Set Editor Game Data |
