.CKO file extension

This is the basic program to work with .CKO extension

ChessBase Light 2007 ChessBase Opening Key

The program works with the following extensions: cit, ck1, ck2, cbs, ck3, cko, ckn, cba, cp1, cbb, cp2, cbc, cp3, cbe, cpn, cbf, cpo, ctb, cbh, ctg, cbm, cto, cbp, pgi, cbt, pgn, cbv, cbz, cib and cbgi

.CKO extension is also supported by the following programs:

ChessBase 9 ChessBase Opening Key

ChessBase ChessBase Opening Key

ChessBase 13 is a personal, stand-alone chess database.

ChessBase Reader ChessBase Opening Key

Open chess games database files and play through the games.