| mods | Mozilla XULRunner Data |
| mof | Managed Object Format File |
| mom | Xcode Managed Object Model |
| momd | Xcode Managed Object Model Bundle Package |
| moo | MoonRock Source Code |
| morph | Squeak MORPH Data |
| mp | MetaPost Source Code |
| mpas | microPascal Pro for PIC Unit |
| mpd | ABC Monadic Predicate Data |
| mpkt | MOPEKS Trial File |
| mplf | CodeWarrior Library |
| mpp | Modgen Source Code |
| mpr | Visual FoxPro Menu Program |
| mprog | FTDI MProg Data |
| mps | Mathematical Programming System Model |
| mpx | Alpha Five Temporary Index |
| mpx | Visual FoxPro Compiled Menu Program |
| mq4 | MetaQuotes Language 4 Source Code |
| mq5 | MetaQuotes Language 5 Source Code |
| mqh | MetaTrader MetaQuotes Language 4 Header |
| mql | MetaTrader MetaQuotes Language 4 File |
| mql4 | MetaTrader MetaQuotes Language 4 File |
| mql5 | MetaTrader MetaQuotes Language 5 File |
| mqt | MetaTrader MetaQuotes Language 4 Template |
| msb | Oracle Binary Message File |
| msct | MOPEKS Script File |
| msh | Microsoft Shell Script |
| msh | MaxL Shell Script |
| msh1 | Microsoft Shell Script |
| msh2 | Microsoft Shell Script |
| msha | Microsoft Help Asset.File |
| mshc | Microsoft Help Container. |
| mshi | Microsoft Help Index.File |
| mshxml | Microsoft Shell Types File |
| msl | ProWorx NXT MSL Loadable |