| mxliff | Memsource XLIFF Data |
| mxm | Maxwell Render Material |
| mxm | Microsoft Project Workgroup Message |
| mxm | MixMeister Studio BPM Calculation Data |
| mxml | Mercury Motif Data |
| mxn | MultiNote Exchangeable Notes |
| mxq | SA Chess MXQ Data |
| mxr | MatrixREDUCE 2.0 PSAM XML Format Data |
| mxrw | Mandelbrot Explorer RAW Data |
| mxs | ArcVIEW Geocode ODB Index |
| mxs | Carlson 2016 Multiple Cross Sections Data |
| mxs | Corel Painter Mixer Pad Data |
| mxsd | IBM WebSphere Message Definition Data |
| mxskin | Maxthon Browser Skin |
| mxt | ArcMAP Template |
| 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 |
| myfourwalls | MyFourWalls Room Model |
| myi | MySQL MyISAM Table Index Data |
| mylic | MySpeed License Key |
| mym | Mymenuify Theme Data |
| mynotesbackup | Keep My Notes Backup Data |
| myo | MYOB AccountRight Company Data |
| myob | MYOB AccountRight Company Data |
