| 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 | Origin LabTalk Script File |
| ogs | Origons Movie Data |
| 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 |
| oid | HP ProCurve Manager Network Device Data |
| oif | Origin Import Filter File |
| ois | Origin Dialog Theme Data |
| oix | Lenne3D Plant Distribution Data |
| ojp | 3WayPack Output |
| ojz | Océ Publisher Compressed Job |
| ok | Dot OK MD5 Hash |
| okd | Lenovo OneKey Recovery Data |
| okozo | Okozo Desktop Animation Data |
| okp | srDraw Dynamic Image Data |
| okr | PowerRecover One Key Recovery File |
| olb | Cadence OrCAD Binary Library Database |
| olb2 | CanOpener Library |
| ole2 | Microsoft Office OLE2 Stream |
| olecf | OLE 2 Compound File |
| olg | OATS Log File |
| olif | Open Lexicon Interchange Format |
| olk | Microsoft Outlook Address Book |
| olk14category | Microsoft Office Outlook for Mac Category Data |