About ecocodes

ecocodes is an independent reference to the ECO opening codes, made by Tristan Edwards. It is not affiliated with Lichess, with the publishers of the Encyclopaedia of Chess Openings or with any chess federation.

The site has one source: the open opening list maintained at lichess-org/chess-openings, which its authors place in the public domain (CC0). Its 3,865 lines are replayed with the python-chess library when the site is built; the boards, counts, comparisons, branches and transpositions shown here are computed from those replays. No game database, engine evaluation or statistic of results is used.

The board diagrams and piece drawings are our own. The meaning of every number is explained on How to read a code page.

Corrections and questions are welcome at support@ecocodes.online. Opening names follow the source list; a name that should change there is best proposed to that project directly.