| mc9 | Mastercam 9 Document |
| mcd | VectorWorks Drawing Document |
| mcdx | Mathcad Prime Document |
| mcf | MasterCook CookBook File |
| mcm | MacMolecule Document |
| mcpat | myriaCross Editor Design 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 |
| mcx-6 | Mastercam X6 Document |
| mcx-9 | Mastercam X9 Document |
| mcx2 | Mastercam X Document |
| mcx5 | Mastercam X5 Document |
| mcx6 | Mastercam X6 Document |
| mcx9 | Mastercam X9 Document |
| md | MarkDown Document |
| md | MuseData Score |
| md | Mayura Draw Document |
| md60 | MacDraft 6.0 Document |
| mda | Microsoft Access Add-in |
| mdb | Microsoft Access Database |
| mdbhtml | Microsoft Access Database HTML Document |
| mdd | Motion Designer Document |
| mdd | MacDraft Drawing Document |
| mde | Microsoft Access Database |
| mdf | JetForm Design Template |
| mdh | Madhyam Document |
| mdk | Madoko Document |
| mdl | Simulink Model |
| mdlp | Simulink Protected Model |
| mdpl | MacDraw II Document |
| mdrw | MacDraw Drawing |
| mdt | Microsoft Access Add-in |