Fritz 21 Handbook

ECO classification

The ECO keys represent a system for classifying chess openings. The name derives from the Encyclopaedia of Chess Openings. The ECO system is an internationally recognised standard for opening classification.

Adding ECO codes

Each key consists of a letter from A to E followed by a two-digit number from 00 to 99. There are 500 keys in total, from A00 to E99.

The ECO keys are an important aid for filtering games with specific openings from a game database. They also have the advantage over verbal opening names that they are much more precisely defined and internationally understood. The program shows a game's ECO key in the status bar at the bottom of the screen and can save the identifier with the game.