| Extension | File Description |
| .MAP | GIS Files |
| .MAP2 | Uncommon Files |
| .MAPF | Uncommon Files |
| .MAPIMAIL | System Files |
| .MAPISEND | Uncommon Files |
| .MAPLET | Game Files |
| .MAPS | Uncommon Files |
| .MAPSAO | Uncommon Files |
| .MAPX | Web Files |
| .MAQ | Database Files |
| .MAR | Database Files |
| .MARCH | Uncommon Files |
| .MARIMBA | Uncommon Files |
| .MARIO | Uncommon Files |
| .MARK | Uncommon Files |
| .MARKDOWN | Text Files |
| .MARKE | Uncommon Files |
| .MARKER | Uncommon Files |
| .MARM | Uncommon Files |
| .MAS | Game Files |
| .MASCOT | Uncommon Files |
| .MASK | Settings Files |
| .MASKA | Uncommon Files |
| .MASON | Uncommon Files |
| .MASS | Uncommon Files |
| .MASSAGESOA | Uncommon Files |
| .MASTER | Web Files |
| .MASTERANDS | Uncommon Files |
| .MAT | 3D Image Files |
| .MATH | Uncommon Files |
| .MATHCALC | Uncommon Files |
| .MATHML | Text Files |
| .MATILDA | Uncommon Files |
| .MAU | Uncommon Files |
| .MAUC | Uncommon Files |
| .MAUD | Uncommon Files |
| .MAV | Database Files |
| .MAW | Database Files |
| .MAX | Raster Image Files |
| .MAXA | Uncommon Files |
| .MAY | Uncommon Files |
| .MAYBE | Uncommon Files |
| .MAZ | Uncommon Files |
| .MAZE | Uncommon Files |
| .MB | 3D Image Files |
| .MB0 | Uncommon Files |
| .MB1 | Uncommon Files |
| .MB2 | Uncommon Files |
| .MB3 | Uncommon Files |
| .MB4 | Uncommon Files |
| .MB5 | Uncommon Files |
| .MB6 | Uncommon Files |
| .MB7 | Uncommon Files |
| .MB8 | Uncommon Files |
| .MB9 | Uncommon Files |
| .MBA | Uncommon Files |
| .MBB | Misc Files |
| .MBC | Uncommon Files |
| .MBD | Data Files |
| .MBE | Uncommon Files |
| .MBF | Backup Files |
| .MBFAVS | Uncommon Files |
| .MBFS | Uncommon Files |
| .MBG | Data Files |
| .MBH | Uncommon Files |
| .MBI | Disk Image Files |
| .MBJ | Uncommon Files |
| .MBK | Backup Files |
| .MBL | Data Files |
| .MBM | Raster Image Files |
| .MBN | Uncommon Files |
| .MBO | Uncommon Files |
| .MBOX | Text Files |
| .MBP | Data Files |
| .MBQ | Uncommon Files |
| Extension | File Description |
| .MBR | Audio Files |
| .MBS | Misc Files |
| .MBSA | Uncommon Files |
| .MBT | Uncommon Files |
| .MBTN | Uncommon Files |
| .MBU | Uncommon Files |
| .MBV | Uncommon Files |
| .MBW | Backup Files |
| .MBX | Data Files |
| .MBY | Uncommon Files |
| .MBZ | Uncommon Files |
| .MC | Uncommon Files |
| .MC$ | Uncommon Files |
| .MC0 | Uncommon Files |
| .MC1 | Data Files |
| .MC2 | Misc Files |
| .MC3 | Uncommon Files |
| .MC3E | Uncommon Files |
| .MC4 | Uncommon Files |
| .MC4D | Uncommon Files |
| .MC5 | 3D Image Files |
| .MC6 | 3D Image Files |
| .MC7 | Uncommon Files |
| .MC8 | Uncommon Files |
| .MC9 | CAD Files |
| .MCA | Game Files |
| .MCB | Uncommon Files |
| .MCC | Uncommon Files |
| .MCD | Data Files |
| .MCE | Uncommon Files |
| .MCF | Font Files |
| .MCG | Uncommon Files |
| .MCH | Uncommon Files |
| .MCHT | Uncommon Files |
| .MCI | Misc Files |
| .MCIF | Uncommon Files |
| .MCJ | Uncommon Files |
| .MCK | Uncommon Files |
| .MCL | Settings Files |
| .MCLEVEL | Game Files |
| .MCM | Uncommon Files |
| .MCN | Uncommon Files |
| .MCO | Misc Files |
| .MCP | Developer Files |
| .MCQ | Uncommon Files |
| .MCR | Executable Files |
| .MCR3 | Uncommon Files |
| .MCR3E | Uncommon Files |
| .MCRE | Uncommon Files |
| .MCS | Raster Image Files |
| .MCT | Uncommon Files |
| .MCU | Uncommon Files |
| .MCURL | Text Files |
| .MCV | Uncommon Files |
| .MCW | Settings Files |
| .MCX | CAD Files |
| .MCY | Uncommon Files |
| .MCZ | Uncommon Files |
| .MC_ | Uncommon Files |
| .MD | Game Files |
| .MD0 | Uncommon Files |
| .MD1 | Disk Image Files |
| .MD2 | Game Files |
| .MD3 | Game Files |
| .MD4 | Uncommon Files |
| .MD5 | Misc Files |
| .MD6 | Uncommon Files |
| .MD7 | Uncommon Files |
| .MD8 | Data Files |
| .MD9 | Uncommon Files |
| .MDA | Plugin Files |
| .MDB | Database Files |
| .MDBACKUP | Backup Files |
| .MDC | GIS Files |
| .MDD | 3D Image Files |
