| .OBR | Micro Focus International plc | Sovelluskehittäjän tiedostot | Borland C++ Object Browser Data | Apache Tomcat | Apache Software Foundation |
| .ODB | Various Developers | Tietokantatiedostot | OpenDocument Database | Apache OpenOffice | Apache Software Foundation |
| .ODC | Microsoft Corporation | Asetustiedostot | Office Data Connection File | Apache OpenOffice | Apache Software Foundation |
| .ODCCUBEFILE | Apache Software Foundation | Harvinaiset Tiedostot | OpenDocument 1 Chart | Apache OpenOffice | Apache Software Foundation |
| .ODF | Oracle Corporation | Harvinaiset Tiedostot | OpenDocument Formula | Apache OpenOffice | Apache Software Foundation |
| .ODG | Apache Software Foundation | Vektorikuvatiedostot | OpenDocument Graphic File | Apache OpenOffice | Apache Software Foundation |
| .ODI | Apache Software Foundation | Rasterikuvatiedostot | OpenDocument Image | Apache OpenOffice | Apache Software Foundation |
| .ODM | Open Source | Tekstitiedostot | OpenDocument Master Document | Apache OpenOffice | Apache Software Foundation |
| .ODP | Oracle Corporation | Datatiedostot | OpenDocument Presentation | Apache OpenOffice | Apache Software Foundation |
| .ODS | Oracle Corporation | Työkirjatiedostot | OpenDocument Spreadsheet | Apache OpenOffice Calc | Apache Software Foundation |
| .ODT | Oracle Corporation | Tekstitiedostot | OpenDocument Text Document | Apache OpenOffice | Apache Software Foundation |
| .OOS | Apache Software Foundation | Työkirjatiedostot | Apache OpenOffice (OpenOffice.org) Spreadsheet | Apache OpenOffice Calc | Apache Software Foundation |
| .OOT | Apache HTTP Project Management Committee | Datatiedostot | Apache OpenOffice Text Document | Apache OpenOffice | Apache Software Foundation |
| .OTC | Apache Software Foundation | Harvinaiset Tiedostot | OpenDocument Chart Template | Apache OpenOffice | Apache Software Foundation |
| .OTG | Apache Software Foundation | Vektorikuvatiedostot | OpenDocument Graphic Template | Apache OpenOffice | Apache Software Foundation |
| .OTH | Apache Software Foundation | Web-tiedostot | OpenDocument HTML Template | Apache OpenOffice | Apache Software Foundation |
| .OTI | Apache Software Foundation | Rasterikuvatiedostot | OpenDocument Image Template | Apache OpenOffice | Apache Software Foundation |
| .OTP | Oracle Corporation | Datatiedostot | OpenDocument Presentation | Apache OpenOffice | Apache Software Foundation |
| .OTS | Apache Software Foundation | Työkirjatiedostot | OpenDocument Spreadsheet Template | Apache OpenOffice | Apache Software Foundation |
| .OTT | Apache Software Foundation | Tekstitiedostot | OpenDocument Document Template | Apache OpenOffice | Apache Software Foundation |
| .OXT | Sun Microsystems | Laajennustiedostot | Apache OpenOffice Extension | Apache OpenOffice | Apache Software Foundation |
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