| msvp | eXtendable Wad Editor MSVP Data |
| msw | Modbus Slave Workspace |
| mswallet | Microsoft Wallet Item Package |
| msxml | Mercury Motif Searches Data |
| msy | MicroSyn Data |
| msz | MediaMonkey v3 Compressed Skin |
| mt5 | Poser Material Data |
| mt940 | SWIFT MT940 Customer Statement Message |
| mta | Samsung AllShare Metadata |
| mtb | Minitab Exec File |
| mtbl | PIPE-FLO Motor Data Table |
| mtc | BrainVoyager QX Mesh Time Course Data |
| mtdt | Trezor Wallet Metadata |
| mte | Noptel NOS Multi-target Data |
| mtf | SDL Trados Translation Memory Translations |
| mtff | MadgeTech 4 Report Data |
| mtg | Making the Grade Data |
| mtgx | Maltego Graph Data |
| mth | Derive Math File |
| mtkey | proDAD Heroglyph License Data |
| mtl | Mastercam Mill Tool Library |
| mtm | 3DCS Model MTM Data |
| mtml | Meaningful Text Markup Language Data |
| mtn | PTC Creo Tool Motion Parameter Data |
| mto | FastCAM MTO Data |
| mtp | SpectraMagic NX Template |
| mtst | MotionTracking RAW Image Stack Data |
| mtt | FastCAM MTO Data Template |
| mtt | MetadataTouch Template |
| mttfs | MadgeTech 4 Report Data |
| mtu | Match! User Database |
| mtw | Minitab Worksheet |
| mu | Quattro Pro for DOS Menu Data |
| mub | ExtractNow Data |
| muc | Music Collector Collection Data |
