| 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 | Mastercam X Document |
| mcx | MICRO CADAM-X/6000 Model Data |
| mcx-5 | Mastercam X5 Document |
| mcx2 | Mastercam X Document |
| mcx5 | Mastercam X5 Document |
| md | Mayura Draw Document |
| md | MarkDown Document |
| md | MuseData Score |
| md60 | MacDraft 6.0 Document |
| mda | Microsoft Access Add-in |
| mdb | Microsoft Access Database |
| mdd | MacDraft Drawing Document |
| mdd | Motion Designer Document |
| mde | Microsoft Access Database |
| mdh | Madhyam Document |
| mdk | Madoko Document |
