| mxq | SA Chess MXQ Data |
| mxr | MatrixREDUCE 2.0 PSAM XML Format Data |
| mxrw | Mandelbrot Explorer RAW Data |
| mxs | ArcVIEW Geocode ODB Index |
| mxsd | IBM WebSphere Message Definition Data |
| mxskin | Maxthon Browser Skin |
| mxt | Fortran 5 Data File |
| mxz | Maximizer CRM Data |
| my3d | Hasbro My3D File |
| myb | MYOB AccountRight Company Data |
| mybible | MySword Bible Database |
| mycolors | Stardock MyColors Theme |
| myd | MySQL MyISAM Table Data |
| mye | MYOB AccountEdge Exported Data |
| myi | MySQL MyISAM Table Index Data |
| mym | Mymenuify Theme Data |
| myo | MYOB AccountRight Company Data |
| myob | MYOB AccountRight Company Data |
| myox | MYOB AccountRight 2011 Company Data |
| mysql | SQL Script |
| mz2 | Maze-Solver Data |
| mz5 | Poser 5 Binary Material Data |
| mzd | Mozy Restore Definition Data |
| mze | Maze Creator Maze Data |
| mzxml | SPC mzXML Data |
| m_p | Pro/ENGINEER Temporary Data |
| n2p | Nebula v2 Program File |
| n2s | Nebula v2 Skin |
| n2u | Baan ERP Native to Unicode Mapping Data |
| n2v | Nebula v2 Vector File |
| n43 | Norma43 Data File |
| n52 | Nostromo n52 Gamepad Configuration Data |
| n64 | N64 ROM Image |
| n80 | PC8001 Rom Image |
| n88 | Apple iOS Kernel Cache |