| mn8 | Microsoft Money 8 Data |
| mnc | Autodesk AutoCAD Compiled Menu |
| mnd | Fractal Forge v2 Fractal Parameters |
| mnf | MSC Adams Model Neutral Data |
| mni | Cerious Mandelbrot Image |
| mnk | My Notes Keeper Notebook |
| mnm | Autodesk Character Studio Marker Name |
| mnr | Autodesk AutoCAD Menu Resource |
| mns | Autodesk AutoCAD Menu Source |
| mnu | General CADD Menu |
| mnu | Autodesk AutoCAD Menu Definition |
| mo1 | Magnavox Odyssey 1 Emulator ROM Image |
| moa | MOA Data File |
| mob | MobTV P2P File |
| mod | ArchiCAD Module File |
| mode | Coda Syntax Mode |
| model | Ribbons Model Definition |
| modfem | Femap Model File |
| moe | Molecular Operating Environment File |
| moef | Motion Effect Template |
| mogrt | Adobe Premiere Motion Graphics Template |
| mojito | LimeWire Kademlia Data |
| mol | Music Module List |
| 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 |
| mono | Monolith Munged Encoded Data |
| mood | Amarok Moodbar Data |
| mopcrt | MOPAC Cartesian Data |
| mopint | MOPAC Internal Data |
| mopout | MOPAC Chemical Output Data |
| mot | MarcEdit Template |