| 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 Representation Data |
| mks | TACT Data File |
| mku | MagicKey Units Definition |
| mkx | Diamino Fashion Suite File |
| mky | MagicKey Configuration Data |
| ml0 | MultiLedger Company Data |
| ml1 | MultiLedger Balance Data |
| ml2 | MultiLedger Budget Data |
| ml3 | MultiLedger Chart of Accounts Data |
| ml4 | MultiLedger Customers Data |
| ml5 | MultiLedger Vendors Data |
| ml6 | MultiLedger Items Data |
| ml7 | MultiLedger Salesperson Data |
| ml8 | MultiLedger Job Data |
| ml9 | MultiLedger Transactions Data |
| mla | Maple Repository File |
| mlb | HP OpenVMS Macro Library |
| mlb | MultiLedger Ship Via Data |