| mud | Autodesk Mudbox Model |
| mug | Hanes T-Shirt Maker Document |
| mup | Music Publisher Score |
| musx | MakeMusic Finale Notation Document |
| mvd | MindView 5 for Mac Document |
| mvdx | MindView for Windows Document |
| mvs | Microchip Verification Specification Data |
| mvtx | MindView for Windows Template |
| mw | Maple Standard Worksheet |
| mw | MacWrite Text Document |
| mwd | Mariner Write Document |
| mwk | Music Write Score Document |
| mwp | Lotus Wordpro Smartmaster File |
| mws | Maple Classic Worksheet |
| mwt | MetaStock Stock Analysis Template |
| mxs | Maxwell Render Scene |
| mytx | MyThoughts for Mac Document |
| myv | Vivaldi Studio Music Score Document |
| myw | MyWorld Education Drawing Document |
| mz | MOZART Music Document |
| mzt | MOZART Score Template |
| n3 | Notation3 Document |
| nb | Mathematica Notebook File |
| nbk | SMART Notebook Document |
| nbml | Mathematica NotebookML File |
| ncd | NoteCase Pro Document |
| ncd | Nero Cover Designer Document |
| nce | NoteCase Pro Encrypted Document |
| nct | Nero Cover Designer Template |
| ncw | Nero Cover Designer Template |
| ncz | NoteCase Pro Compressed Document |
| nd | Intuit QuickBooks Network Data File |
| ndg | Network Notepad Network Diagram |
| ndo | Nendo Enhanced Native File |
| ndoc | Naver Word Document |
