Files with the .OBI extension contain RSS feed subscription names and properties saved in the XML format for the Microsoft Outlook profile. They are used to store subscription information in Microsoft's calendar and email clients.

File naming is based on the user profile name, namely [profile_name].Sharing.XML.Obi. The files are saved by default in the C:UsersUser_nameName_Users/Data_Data_Data_Name].Sharing.XML.Obi, are saved by default in the C:Users[user_name]AppDataLocalMicrosoftOutlook directory. You can export them to the more versatile Outline Processor Markup Language format, or OPML for short, using the RSS feed export option in MS Outlook.