| man | Unix Manual Page |
| maq | Microsoft Access Query |
| mar | Microsoft Access Report |
| marc | MARC Document |
| mars | Adobe MARS Document |
| mas | Microsoft Access Stored Procedure |
| mat | Microsoft Access Table |
| mathml | Mathematical Markup Language Document |
| mau | Microsoft Access Function Shortcut |
| mav | Microsoft Access View Shortcut |
| maw | Microsoft Access Data Access Page |
| max | Autodesk 3D Studio Max Scene |
| mb | Autodesk Maya 3D Binary Scene |
| mb | Mathematica Binary File |
| mb3 | Minimal Board Editor Document |
| mb4 | Model Builder Document |
| mbb | ManaBook Document |
| mbbk | ManaBook Book Kit |
| mbf | Microsoft Money Backup |
| mbk | SmartWare Macro Backup |
| mbxml | meBible XML File |
| mc2 | MasterCook 5 CookBook File |
| mc8 | Mastercam 8 Document |
| mc9 | Mastercam 9 Document |
| mcd | VectorWorks Drawing Document |
| mcdx | Mathcad Prime Document |
| mcf | MasterCook CookBook File |
| mcm | MacMolecule Document |
| mcr | C.a.R. Macro |
| mcw | Microsoft Word for Macintosh Document |
| mcx | MICRO CADAM-X/6000 Model Data |
| mcx | Mastercam X Document |
| mcx-5 | Mastercam X5 Document |
| mcx2 | Mastercam X Document |
| mcx5 | Mastercam X5 Document |
