| mrd | MathRevolt Ininity Document |
| mrml | 3D Slicer Scene Description |
| mrml | Medical Reality Modeling Language File |
| mro | SharpEye Music Reader Document |
| mrp | MathRevolt Ininity Plot |
| ms10 | NI Multisim 10 Circuit Design |
| ms11 | NI Multisim 11 Circuit Design |
| ms12 | NI Multisim 12 Circuit Design |
| ms13 | NI Multisim 13 Circuit Design |
| ms14 | NI Multisim 14 Circuit Design |
| ms3d | MilkShape 3D Model |
| ms7 | NI Multisim 7 Circuit Design |
| ms8 | NI Multisim 8 Circuit Design |
| ms9 | NI Multisim 9 Circuit Design |
| mscx | MuseScore Music Score |
| mscz | MuseScore Compressed Music Score |
| msg | Microsoft Outlook E-Mail Message |
| msim | MapleSim Model |
| mtd | Musicnotes Digital Sheet Music |
| mtf | MasterCook Document |
| mts | Viewpoint MTS Document |
| mud | Autodesk Mudbox Model |
| mug | Hanes T-Shirt Maker Document |
| mup | Music Publisher Score |
| musx | MakeMusic Finale Notation Document |
| mvd | MindView 5 for Mac Document |
| mvdx | MindView for Windows Document |
| mvs | Microchip Verification Specification Data |
| mvtx | MindView for Windows Template |
| mw | MacWrite Text Document |
| mw | Maple Standard Worksheet |
| mwd | Mariner Write Document |
| mwk | Music Write Score Document |
| mwp | Lotus Wordpro Smartmaster File |
| mws | Maple Classic Worksheet |
