File Extension OBX File Format OpenBook document file OBX stands for OpenBook document 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 Opening MDB file with Apple iBook All of my files are changing to CCC files How do I create a new local names.nsf file.