| orj | InterSelect PhotoScan Data |
| orl | Object-Relational Language Data |
| orm | Ormetis Workbench Data |
| ormv | Ormetis View Data |
| oro | 3WayPack T3Rotate Output |
| orp | Microsoft Translator for Android Resources Data |
| orp | WinSLAMM ORP Data |
| orq | OCSP Request Data |
| orx | RadiantOne VDS Database Schema |
| ory | Act! Opportunities Query Data |
| os | Altair FEKO POSTFEKO Currents Data |
| os2 | OS/2 Warp System File |
| os3 | OS/2 Warp 3 System Data |
| osa | JD Edwards EnterpriseOne OSA File |
| osbx | OneSafe Backup Archive |
| osc | OpenStreetMap Change |
| oscd | TouchOSC Interface Editor Template |
| oset | Marmoset OSET Data |
| osf | Opera Skin Data |
| osh | IBM InfoSphere Schema Data |
| osi | Osiris Data |
| osis | Open Scriptural Information Standard Data |
| osl | OckamSoft 4 Log |
| osl | Orbit Symbol Library |
| osm | OpenStreetMap Map |
| osm | WaterGEMS Outage Segmentation Results Data |
| ospx | Dell KACE Patch Definition FIle |
| oss | Microsoft Office Outlook Saved Search |
| ost | Microsoft Outlook Offline Folder File |
| osw | ONESWING Contents Data |
