ECO codes: chess openings from A00 to E99
The Encyclopaedia of Chess Openings code splits openings into five groups, A to E, and 100 numbers in each. Below are the 324 codes that our 954 opening pages fall under, with every page linked.
A: Flank openings: 1.c4, 1.Nf3, 1.b3, 1.f4 and 1.d4 without an early ...d5 or ...Nf6 ...e6 setups
B: Semi-open games after 1.e4 other than 1...e5 and 1...e6: Sicilian, Caro-Kann, Pirc, Alekhine, Scandinavian
C: Open games (1.e4 e5) and the French Defense
D: Closed games: 1.d4 d5, the Queen's Gambit, Slav and Grünfeld
E: Indian defenses with 1.d4 Nf6 2.c4 e6 or ...g6: Catalan, Nimzo-Indian, Queen's Indian, King's Indian
Questions
What are ECO codes in chess?
ECO codes classify chess openings with a letter from A to E and a number from 00 to 99, 500 codes in all. The letter marks a broad group of openings and the number narrows it to a family or variation.
What does each ECO letter mean?
A: Flank openings: 1.c4, 1.Nf3, 1.b3, 1.f4 and 1.d4 without an early ...d5 or ...Nf6 ...e6 setups. B: Semi-open games after 1.e4 other than 1...e5 and 1...e6: Sicilian, Caro-Kann, Pirc, Alekhine, Scandinavian. C: Open games (1.e4 e5) and the French Defense. D: Closed games: 1.d4 d5, the Queen's Gambit, Slav and Grünfeld. E: Indian defenses with 1.d4 Nf6 2.c4 e6 or ...g6: Catalan, Nimzo-Indian, Queen's Indian, King's Indian.
Can one opening have more than one ECO code?
Yes. A named line can be reached through several codes, and some lichess opening names span two codes. Each page here lists every code attached to its line.