20 File Extensions starting with O
| .OAZ | OAZ Fax Image |
| .OCP | Advanced Art Studio Image |
| .ODB | ODF Database |
| .ODF | ODF Formula |
| .ODG | ODF Drawing Presentation |
| .ODM | ODF Master Document |
| .ODP | ODF Presentation |
| .ODS | ODF Spreadsheet |
| .ODT | ODF Text Document |
| .OFX | Olicom Fax Image |
| .OGG | Ogg Multimedia Container File |
| .OGM | Ogg Multimedia Container File |
| .OIL | Open Image Library Format Image |
| .OMA | OpenMG Audio File |
| .ORF | Raw Image File |
| .OTB | Nokia OTA Image |
| .OTH | HTML Document Template |
| .OTP | ODF Presentation Template |
| .OTS | ODF Spreadsheet Template |
| .OTT | ODF Text Document Template |