Openings

Every chess opening is filed under one of just 500 ECO codes(A00–E99), grouped into five volumes:

• A — Flank openings (English 1.c4, 1.Nf3, irregular lines)
• B — Semi-open games except the French (Sicilian, Caro-Kann…)
• C — Open games 1.e4 e5 and the French 1.e4 e6
• D — Closed & semi-closed 1.d4 d5 (Queen’s Gambit, Grünfeld…)
• E — Indian defences (Nimzo-Indian, King’s Indian…)

A single code is a family: e.g. C50 covers the whole Italian Game / Giuoco Piano complex, so the Giuoco Piano, Giuoco Pianissimo, Hungarian Defense and Two Knights all live under C50. That’s why one code maps to many named variations — the code is the family, the name is the specific line. ChessEyes shows you both.