| mol | MDL Molecule File |
| mol2 | Tripos Mol2 Format File |
| mologiq | HTC EVO 3D Data |
| mon | Steinberg WaveLab Audio Montage |
| mon2 | UltraSite Graphical Status Data |
| moneywell | MoneyWell Account Data |
| mongodb | MongoDB Database |
| mono | Monolith Munged Encoded Data |
| monte | CRiSP Monte Carlo Method Data |
| mood | Amarok Moodbar Data |
| mopcrt | MOPAC Cartesian Data |
| mopint | MOPAC Internal Data |
| mopout | MOPAC Chemical Output Data |
| mot | MarcEdit Template |
| mot | Animation Master Motion Data |
| moti | Motion Title Template |
| motr | Motion Transition Template |
| mow | OvenWATCH Workbook |
| mox | ExtendSim Simulation Model |
| moz | Netscape Navigator Temporary File |
| mozeml | Thunderbird Spotlight Searchable Email |
| mozmsgs | Thunderbird Mail Folder |
| mp | Race Studio 2 Map File |
| mp | MatrixPlot Data |
| mp+ | Incite Media Assistant File |
| mp21 | AXMEDIS MPEG21 Data |
| mp5 | Maple Data |
| mp6 | CS225 MP6 Huffman Encoding Text Data |
| mpa | Mail.dat Postage Account File |
| mpack | Mpack Encoded MIME Message |
| mpb | My Phone Explorer Data |
| mpb | Music Publisher Backup File |
| mpcatalog | Phase One Media Pro Catalog |
| mpcb | ReliaSoft MPC Data |
| mpd | Xilinx Microprocessor Peripheral Definition |