File Extension OSD File Format OSD4 data file OSD stands for OSD4 data file. This was last updated in March 2012 By Margaret Rouse Browse File Extensions Alphabetically: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # Ask a Question. Find an Answer. Ask your peers a question about this file extension. Ask a Question About object storage devices Adding permissions Outlook contacts are not able to be searched by other users.