ChessmateGet the appECO code
Encyclopaedia of Chess Openings codeAn ECO code classifies opening positions with a letter from A to E and two digits.
The code groups related openings even when their names or move orders vary. It identifies an opening family rather than explaining how to play it.
ECO runs from A00 to E99
The Encyclopaedia of Chess Openings classification has five letter groups with one hundred numeric codes each. Together they provide 500 broad slots for organizing opening families and branches.
| Range | Typical coverage |
|---|---|
A00-A99 | Flank openings and several non-1.e4 systems |
B00-B99 | Many 1.e4 openings including the Sicilian |
C00-C99 | French and many 1.e4 e5 openings |
D00-D99 | Many 1.d4 d5 and Grünfeld systems |
E00-E99 | Many Indian systems |
An ECO code is a category, not a complete move sequence
A single code can cover several named variations, and a named opening can span multiple codes. Databases may also choose a code after recognizing a later position reached through a transposition.
Use ECO to group games, then inspect the moves
ECO is useful for filtering a database or finding related courses, but the code alone does not tell you which side, move order, or branch a specific training line uses. Read it together with the opening name and movetext.