| mfst | Symantec Endpoint Protection Definitions Manifest Data |
| mftpkg | MacFamilyTree Project Package |
| mg | MetaGuide Setup Data |
| mgc | Equation Illustrator Main Data File |
| mgc | Media Catalog MGC File |
| mgd | Master Grade Data |
| mgd77 | MGD77 Format Data |
| mgf | Materials and Geometry Format Data |
| mgh | MGH MRI Data |
| mgi | Magellan eXplorist Map Image |
| mgjson | Adobe After Effects Motion Graphics JSON Data |
| mgm | Equation Illustrator Macro |
| mgo | MacGourmet Recipe |
| mgrp | NI Maschine Group File |
| mgrs | Military Grid Reference System Data |
| mgspot | MacGourmet Spotlight MetaData |
| mgtheme | MacGourmet Theme |
| mgw | Microgateway Policy Implementation Data |
| mgz | Compressed MGH MRI Data |
| mhd | ITK MetaImage Header |
| mhe | Hackshield Heuristic Engine File |
| mhg | MHEG-5 Multimedia Data |
| mhl | Media Hash List |
| mhm | Microsoft Mouse and Keyboard Center Macro |
| mhp | Maths Helper Plus Data |
| mhs | Xilinx Microprocessor Hardware Specification |
| mi2 | AutoDesk Softimage Data |
| miaf | InstallAware Setup Dialog Rules |
| mib | SNMP MIB File |
| midata | Mine-imator Data |
| mif | Xilinx CORE Generator Memory Initialization File |
| mif | mAirList Inline File |
| mif | Elmer Mesh Generator Input File |
| miframes | Mine-imator Keyframes Data |
| miigx | SaveGame Manager GX Mii Data |