Explore the Encyclopaedia of Chess Openings (ECO) classification from A00 to E99. Search codes, identify opening names and families, and use each classification as a starting point for further line and position study. Explore the CAISSA Opening Database when you are ready to continue.
Board preview coming soon.
Continuations will be computed from PGNs/DB soon.
Pick an ECO code from the left list to see details.
The Encyclopaedia of Chess Openings classifies established opening lines across the range A00–E99. Each code begins with a letter that places the opening in a broad family, while the two digits narrow that family to a more specific opening, system, or group of variations. This compact structure gives players a consistent way to organize and compare opening knowledge without relying on names alone.
ECO codes are useful reference labels, not a substitute for studying positions. A single code may cover several related move orders, and the same position can sometimes be reached through a transposition from another opening sequence. Use the searchable list above to connect a code with its opening name and defining moves, then continue in the CAISSA Opening Database to explore how the position develops in practical games. Treat the classification as a map: it helps locate an opening family, while the board and move data provide the detail.