| nxp | NEXUS Expansion Pack |
| nxs | NEXUS Data File |
| nyf | myBase Database |
| nyl | Novapoint Vertical Alignment Data |
| nym | Sheffield Dictionary Data |
| oa | OpenAccess Database |
| oab | Microsoft Outlook Offline Address Book |
| 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 | WAsP Obstacle List |
| obskin | ObjectBar Skin |
| obu | WindLDR Device Data List |
| obx | IBM Rational XDE Object File |
| oc3 | OpenCanvas 3 Event |
| oc4 | OpenCanvas 4 Event |
| oc5 | OpenCanvas 5 Event |
| oc8 | OrgCon 8 Organization Data |
| oc9 | OrgCon 9 Organization Data |
| ocb | DOpus Configuration Backup |
| occ | DB/TextWorks List of BTX Records |
| occ | OptControlCentre Model |
