| mfn | MODFLOW Name Dataset |
| mfo | MobileFrame Object Data |
| mfr | Moldflow Result |
| mfs | MetFS Encrypted File System |
| mfst | Symantec Endpoint Protection Definitions Manifest Data |
| mftpkg | MacFamilyTree Project Package |
| mfx | MADRIX Fixture Fix Data |
| mfxp | NI Maschine v1 Effects Plug-in Presets Data |
| mg | MetaGuide Setup Data |
| mga4 | Mageia Linux 4 Data |
| mga5 | Mageia Linux 5 Data |
| mgc | Equation Illustrator Main Data File |
| mgc | Media Catalog MGC File |
| mgd | Master Grade Data |
| mgd77 | MGD77 Format Data |
| mgdatabase | MacGourmet Deluxe Database |
| mgf | Materials and Geometry Format Data |
| mgf | Minitab Graph Data |
| mgh | MGH MRI Data |
| mgi | Magellan eXplorist Map Image |
| mgjson | Adobe After Effects Motion Graphics JSON Data |
| mgm | Equation Illustrator Macro |
| mgn2 | Bloody Mouse Macro Data |
| mgo | MacGourmet Recipe |
| mgrp | NI Maschine v1 Group Data |
| mgrs | Military Grid Reference System Data |
| mgspot | MacGourmet Spotlight MetaData |
| mgt | SWAT Management Input Data |
| 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 |
