| Extension | File Description |
| .OJQ | Uncommon Files |
| .OJR | Uncommon Files |
| .OJS | Uncommon Files |
| .OJT | Uncommon Files |
| .OJU | Uncommon Files |
| .OJV | Uncommon Files |
| .OJW | Uncommon Files |
| .OJX | Uncommon Files |
| .OJY | Uncommon Files |
| .OJZ | Uncommon Files |
| .OK | Uncommon Files |
| .OK0 | Uncommon Files |
| .OK1 | Uncommon Files |
| .OK2 | Uncommon Files |
| .OK3 | Uncommon Files |
| .OK4 | Uncommon Files |
| .OK5 | Uncommon Files |
| .OK6 | Uncommon Files |
| .OK7 | Uncommon Files |
| .OK8 | Uncommon Files |
| .OK9 | Uncommon Files |
| .OKA | Uncommon Files |
| .OKB | Uncommon Files |
| .OKC | Uncommon Files |
| .OKD | Uncommon Files |
| .OKE | Uncommon Files |
| .OKF | Uncommon Files |
| .OKG | Uncommon Files |
| .OKH | Uncommon Files |
| .OKI | Uncommon Files |
| .OKJ | Uncommon Files |
| .OKK | Uncommon Files |
| .OKL | Uncommon Files |
| .OKM | Uncommon Files |
| .OKN | Uncommon Files |
| .OKO | Uncommon Files |
| .OKP | Uncommon Files |
| .OKQ | Uncommon Files |
| .OKR | Uncommon Files |
| .OKS | Uncommon Files |
| .OKT | Audio Files |
| .OKU | Uncommon Files |
| .OKV | Uncommon Files |
| .OKW | Uncommon Files |
| .OKX | Uncommon Files |
| .OKY | Uncommon Files |
| .OKZ | Uncommon Files |
| .OL0 | Uncommon Files |
| .OL1 | Uncommon Files |
| .OL2 | Uncommon Files |
| .OL3 | Uncommon Files |
| .OL4 | Uncommon Files |
| .OL5 | Uncommon Files |
| .OL6 | Uncommon Files |
| .OL7 | Uncommon Files |
| .OL8 | Uncommon Files |
| .OL9 | Uncommon Files |
| .OLA | Uncommon Files |
| .OLB | CAD Files |
| .OLC | Uncommon Files |
| .OLD | Backup Files |
| .OLDEST | Uncommon Files |
| .OLE | Uncommon Files |
| .OLF | Uncommon Files |
| .OLG | Uncommon Files |
| .OLH | Uncommon Files |
| .OLI | Uncommon Files |
| .OLJ | Uncommon Files |
| .OLK | Data Files |
| .OLL | Uncommon Files |
| .OLLIEFONT | Uncommon Files |
| .OLM | Uncommon Files |
| .OLN | Uncommon Files |
| .OLO | Uncommon Files |
| .OLP | Uncommon Files |
| Extension | File Description |
| .OLQ | Uncommon Files |
| .OLR | Uncommon Files |
| .OLRW | Uncommon Files |
| .OLS | Uncommon Files |
| .OLSR | Uncommon Files |
| .OLT | Data Files |
| .OLU | Uncommon Files |
| .OLV | Uncommon Files |
| .OLW | Uncommon Files |
| .OLX | Uncommon Files |
| .OLY | Uncommon Files |
| .OLZ | Uncommon Files |
| .OM | Uncommon Files |
| .OM0 | Uncommon Files |
| .OM1 | Uncommon Files |
| .OM2 | Uncommon Files |
| .OM3 | Uncommon Files |
| .OM4 | Uncommon Files |
| .OM5 | Uncommon Files |
| .OM6 | Uncommon Files |
| .OM7 | Uncommon Files |
| .OM8 | Uncommon Files |
| .OM9 | Uncommon Files |
| .OMA | Audio Files |
| .OMB | Uncommon Files |
| .OMC | Uncommon Files |
| .OMCS | Data Files |
| .OMD | Uncommon Files |
| .OMDOC | Data Files |
| .OME | Uncommon Files |
| .OMF | Raster Image Files |
| .OMG | Audio Files |
| .OMH | Uncommon Files |
| .OMI | Uncommon Files |
| .OMJ | Uncommon Files |
| .OMK | Uncommon Files |
| .OML | Uncommon Files |
| .OMM | Uncommon Files |
| .OMN | Uncommon Files |
| .OMO | Developer Files |
| .OMOD | Game Files |
| .OMP | Data Files |
| .OMQ | Uncommon Files |
| .OMR | Uncommon Files |
| .OMS | Uncommon Files |
| .OMT | Uncommon Files |
| .OMU | Uncommon Files |
| .OMV | Uncommon Files |
| .OMW | Uncommon Files |
| .OMX | Audio Files |
| .OMY | Uncommon Files |
| .OMZ | Uncommon Files |
| .ON | Uncommon Files |
| .ON0 | Uncommon Files |
| .ON1 | Uncommon Files |
| .ON2 | Uncommon Files |
| .ON3 | Uncommon Files |
| .ON4 | Uncommon Files |
| .ON5 | Uncommon Files |
| .ON6 | Uncommon Files |
| .ON7 | Uncommon Files |
| .ON8 | Uncommon Files |
| .ON9 | Uncommon Files |
| .ONA | Uncommon Files |
| .ONB | Uncommon Files |
| .ONC | Uncommon Files |
| .OND | Data Files |
| .ONE | Data Files |
| .ONEPKG | Backup Files |
| .ONETMP | Misc Files |
| .ONETOC | Data Files |
| .ONETOC2 | Settings Files |
| .ONF | Uncommon Files |
| .ONG | Uncommon Files |
| .ONH | Uncommon Files |
