| 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 |
| mjf | Magnet Field Job Data |
| mjk | Adobe Illustrator Mojikumi Set |
| mjm | JMF Mime Package |
| mjp | JRiver Media Center Plugin |
| mjr | Media Jukebox Portable License Data |
| mjs | Mijas 7400 Costing Database |
| mjx | Objectif Lune Sugopita Data |
| mk2 | Flowcom 32 Data |
| mk4 | Akregator Data |
| mk4 | Schiller Medilog ECG Raw Data File |
| mkb | DVD Audio Media Key Block |
| mkc | MagicKey Currency Exchange Rate Data |
| mkd | Agilent ChemStation Multicell Kinetic Disk Data |
| mkd | Pervasive SQL Database |
| mke | Windows SDK Makefile |
| mkelem | IBM Rational ClearCase MKELEM Data |
| mkext | Mac OS X Mach Kernel Extension Cache |
| mkg | MokkAnnotator Mokkan Glass Data |
| mkh | WinMark Pro Mark Data |
| mkl | CAD6 Library |
| mklk | CyberLink MakeupDirector Look Data |
| mkn | PEARLNEQ MKN Input Data |
| mkr | my Knowledge Explorer Knowledge Representation |
| mkr | my Knowledge Representation Data |
