| maplib | Mscape Map Data |
| mapx | MapDotNet UX Map File |
| mar | Pegasus Mail Attribute Record Data |
| marker | Microsoft Windows 10 System Data |
| markers | BEAGLE Markers Data |
| marshal | Marshal Data Migration Model |
| mash | Java Mashing Data |
| mask | Adobe SpeedGrade Color Mask |
| mat | Altair FEKO Matrix Element Data |
| mat | Animation Master Material Data |
| mat | Bryce 3D Material Data |
| mat | Kerkythea Material Data |
| mat | Pro/ENGINEER Material Properties Data |
| material | Rigs of Rods Texture Reference |
| math | AnalyticMath Data |
| matl | Sonnet Substrate Data |
| matplot | Matplotlib Plot |
| matx | eXtendable Wad Editor MATX Data |
| mauve | Mauve Alignment Data |
| maxc | Autodesk 3D Studio MAX Container |
| maxd | PaperPort Annotation Data |
| maxfr | MaxView Web Pointer Data |
| maxm | PaperPort Data |
| maz | dVISE 3D Model |
| mb1 | Math Blaster 1 Data |
| mb1 | UltraEdit Menus Data |
| mba | Martus Human Rights Bulletin System Data |
| mbak | Quantrix Modeler Backup Data |
| mbb | CARAIBES Bathymetric Data |
| mbbackup | Modelbench Backup Data |
| mbdata | Modelbench Scene Data |
| mbdb | iTunes Backup Manifest Database |
| mbdx | iTunes Backup Manifest Database |
| mbg | CARAIBES Georeferenced Depth Data |
| mbg | Microsoft Mail Mailbag |
