| ovd | OverDisk Data |
| overlay | Streamlabs OBS Overlay Data |
| ovf | Open Virtualization Format Data |
| ovi | PC-9801 FM System Data |
| ovisuite | Nokia Ovi Suite Data |
| ovl | E-Sword v8 Overlay Data |
| ovlx | E-Sword v9 Overlay Data |
| ovm | BHV Tonstudio Data |
| ovml | Ovidentia Markup Language Document |
| ovolog | ooVoo Log File |
| ovs | ARTA Overlay Data |
| ovt | Orbit Vector File Tiled |
| ovw | Cubase WAVE File Overview |
| owc | OutWit Hub OutWit Catch Database |
| owc | WAsP Observed Wind Climate |
| owf | OSRAM Waveform File |
| owg | OutWit Hub Gear Database |
| owm | OutWit Hub XML Mashup |
| owt | OneWorldTree Data |
| owx | OutWit Hub Script |
| oxb | OlapX Report Portfolio Data |
| oxc | OlapX Cube Definition |
| oxd | PS3 Proxy Server Data |
| oxe | Pulsar Z.matrix Data |
| oxf | Origin X-Function File |
| oxl | LITESTAR 4D Data File |
| oxml | OXML 2.0 Data |
| oxp | OmniRush eXtended Package |
| oxy | Matplotlib OXY Data |
| oyx | Lotus Approach Alternate Database Index |
| oz | Opera Job Management Compressed File |
| ozd | OZ Report Data |
| ozp | Sharp Wizard Phone Bank Data |
| p00 | Commodore 64 Program Image |
| p01 | MicroStation Modification Project Resource File |