| odx | Microsoft BizTalk Server Orchestration File |
| oe3 | OpenCanvas 3 Event Data |
| oe4 | OpenCanvas 4 Event Data |
| oe5 | OpenCanvas 5 Event Data |
| oeaccount | Windows Mail Account Data |
| oeb | Outlook Express Backup Wizard Data |
| oec | OE-Cake File |
| oef | IBM Optim Export Format Data |
| oes | OpenCanvas 2 Event Data |
| oet | eSignal Order Entry Ticket Data |
| ofa | Kodak OfotoNow Data |
| off | AquaCrop Off-season Field Data |
| off | Geomview Binary OFF Data |
| ofl | OtsAV File List |
| ofl_en | OtsAV File List |
| ofm | Melco Embroidery Data |
| ofm | TopLevel OfficeForms Blank Form |
| ofr | Microsoft SMS Offer File |
| ofv | DOpus Saved Favorites |
| ofw | TopLevel OfficeForms Form |
| ogc | Impulse Organica Model Data |
| ogex | Open Game Engine Exchange Data |
| ogg | Origin Graphs Data |
| ogl | Molden OpenGL Model |
| ogm | Origin Matrix Data |
| ogo | Origin Graphic Object |
| ogs | Origons Movie Data |
| ogs | Origin LabTalk Script File |
| ogw | Origin Worksheet Data |
| ogwu | Origin Unicode Worksheet Data |
| oh | DrillAssistant List Data |
| oha | Ohanae Encrypted Data for Sharing |
| ohanae | Ohanae Encrypted Data for Privat Use |
| oht | Oracle Help for Java Links Data |
| ohw | DrillAssistant List Data |