| mil | PTC Creo Milling Parameter Data |
| milanguage | Mine-imator Language Data |
| millpst | BobCAD-CAM Post Processor Data |
| mim | MIME Encoded Data |
| mime | MIME Encoded Data |
| mimodel | Mine-imator Model Data |
| mindnode | MindNode Document |
| mini | Mini V Presets Data |
| minibank | Mini V Presets Data |
| miniml | MINiML File |
| miobject | Mine-imator Object Data |
| miparticles | Mine-imator Particles Data |
| mir | Mail.dat Manifest Individual File |
| mit | MineEdit Inventory Template |
| miv | MapImagery Vendor Profile |
| mix | VentaFax Voice Message Batch |
| mixn | Apple Guide Addition Data |
| mi_ | Compressed MID File |
| mj | MovieJack DVD Ripper File |
| mj | Palladio ModelJoin Query File |
| mj4 | Objectif Lune Sugopita Data |
| mjd | Mime-encoded JDF |
| mjk | Adobe Illustrator Mojikumi Set |
| mjm | JMF Mime Package |
| mjs | Mijas 7400 Costing Database |
| mjx | Objectif Lune Sugopita Data |
| mk4 | Schiller Medilog ECG Raw Data File |
| mkb | DVD Audio Media Key Block |
| mkd | Pervasive SQL Database |
| mkelem | IBM Rational ClearCase MKELEM Data |
| mkg | MokkAnnotator Mokkan Glass Data |
| mkh | WinMark Pro Mark Data |
| mkl | CAD6 Library |
| mkn | PEARLNEQ MKN Input Data |
| mkr | my Knowledge Representation Data |