| nyl | Novapoint Vertical Alignment Data |
| nym | Sheffield Dictionary Data |
| nzl | Corel Painter Nozzle Data |
| nzn | NoteZilla Notes Data |
| nzn | RMCProfile Nitrogen Zinc Neighbours Data |
| o8c | OCTGN Card Image |
| o8d | OCTGN Deck Data |
| o8g | OCTGN Game Definition Data |
| o8s | OCTGN Set Data |
| oa | OpenAccess Database |
| oab | Microsoft Outlook Offline Address Book |
| oal | Forms Design Tool Pattern License Data |
| oam | Adobe Edge Animate Widget |
| oaw | OpenArchitectureWare Workflow Data |
| ob | IBM LinkWay Object |
| ob! | Orbit Downloader Unfinished File |
| ob3 | ORTIMzeit Data File |
| obc | AICON 3D Photogrammetry File |
| obi | Microsoft Outlook RSS Subscription Data |
| obj | Wavefront Object File |
| obk | Oxygen Phone Manager Phone Book Data |
| obk | Genie Outlook Express Backup Data |
| obpack | ObjectBar Theme |
| obs | AquaCrop Field Observations Data |
| obs | WAsP Obstacle List |
| obskin | ObjectBar Skin |
| obu | WindLDR Device Data List |
| obx | pCon.planner Pro OBX Exchange Format Data |
| obx | IBM Rational XDE Object File |
| oc | MODFLOW Output Control Data |
