This page provides a list of those file extensions that start with .o. The information given below is a summary and further details can be found by clocking on the summary next to the file extension of interest.

.oObject file.
.objObject file (Windows).
.oblInstallScript library file.
.ocaVB cache file.
.ocxActiveX control.
.odMascopt graph request file.
.odcMicrosoft Office Data Connection file.
.odsOpenOffice spreadsheet | Outlook Express mailbox.
.odtOpenDocument Text document | Virtual Reality Explorer Kit Object file.
.oebOpen eBook file.
.oftOutlook form template file.
.oggOgg Vorbis music file.
.oldGeneric old or backup file.
.oneMicrosoft OneNote file.
.opfFlipBook definition file.
.opsMicrosoft Outlook Profile Settings file.
.optVisual studio workspace information file.
.orfOlympus Raw File | Descent 3 Outrage Room Format file | Override Rules File.
.ostExchange offline storage file.
.ovlDriveimage setup file | Overlay file.

For further information about the file extension please do click on the summary next to the file extension in the list above.

We would like this listing to be complete and comprehensive, but recognised that we may have missed one and that new file types are being used all the time. So if you know of a file type that we have missed that should be listed here then please let us know.