| mlb | FoxPro 2 for Macintosh Library |
| mlc | Message Tools for NetWare Source Code |
| mlh | Message Tools for NetWare Source Code |
| mli | OCaml Interface Source |
| mlib | MATLAB Shared Library |
| mlua | MetaLua Source Code |
| mlv | LabVIEW Mathscript |
| mlw | WhyML Program |
| mly | OCaml Ocamlyacc Input Data |
| mmb | Oracle Forms Menu Module Binary |
| mmk | MACSIMUS Metamake Data |
| mmo | WinDev HyperFileSQL Memo File |
| mmpa | MoreMotion Page |
| mmpf | CodeWarrior Preferences Data |
| mmt | Oracle Forms Menu Module Text |
| mmx | Oracle Forms Menu Module Executable |
| mn8 | SpaceMapper MN8 Script |
| mnft | Java Manifest File |
| mno | Dreamweaver Design Notes Data |
| mnt | Visual FoxPro Menu Memo |
| mntr | ANSYS Monitor Data |
| mnw | WinBatch Menu Data |
| mnx | Visual FoxPro Menu Template |
| mo | GNU Gettext Machine Object File |
| mobileprovision | Provisioning Profile |
| moc | QT Meta-Object Compiler File |
| 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 |
| mos | Xpress Mosel Source Model |
| mosel | Xpress Mosel Source Model |
| mp | MetaPost Source Code |