Chess Opening Encyclopedia
Explore our comprehensive database of chess openings, organized by ECO codes. Learn the theory, strategies, and key variations of every major chess opening.
Open Games
C00-C99Classical 1.e4 e5 openings including the Ruy Lopez, Italian Game, and King's Gambit.
Semi-Open Games
B00-B99Asymmetrical responses to 1.e4, including the Sicilian, French, and Caro-Kann Defenses.
Closed Games
D00-D99Queen's Pawn openings including the Queen's Gambit and related systems.
Indian Defenses
E00-E99Modern defenses against 1.d4 including the King's Indian and Nimzo-Indian.
Flank Openings
A00-A99Alternative first moves including the English Opening and Réti Opening.
Understanding ECO Codes
The Encyclopedia of Chess Openings (ECO) is a classification system for chess openings, providing a standard code for every major variation. The system uses letters A through E, each followed by two digits.
- A00-A99: Irregular openings and flank openings
- B00-B99: Semi-open games (1.e4 with replies other than 1...e5)
- C00-C99: Open games (1.e4 e5)
- D00-D99: Closed games and semi-closed games (1.d4 d5)
- E00-E99: Indian defenses and other queen pawn games
