ECO classification

The abbreviation ECO stands for “Encyclopedia of Chess Openings” , a standard reference for openings that is published by the Chess Informant. Individual variations of an opening are denoted by abbreviations like “C43” (Petroff with 3.d4) or “D89” (Grunfeld Indian Exchange – main line). The system has become universally accepted and is also used by ChessBase.

In the search mask you can specify a range of openings (and combine this with players, length, result, etc.). Click on the ECO checkbox and enter ECO codes, e.g.

“C43”	and	“C45”	for all games from C43 to C45
“C”	and	“C45”	for all games from C00 to C45
“C45”	and	nothing	for all games from C45

The number behind the slash in the code (“/99”) denotes the subvariations.

The ECO code is embedded in all games supplied by ChessBase and displayed in the games list. If a set of game you get from somewhere else does not contain or has incorrect ECO codes you can have them inserted by ChessBase.

Use Games list: Games – Set ECO codes

This will insert or correct the ECO codes in all the games.

1.	Volume C covers the French Defense and all double King pawn openings.

2.	Volume B covers all 1.e4 openings in which Black replies with something other than 1.e6 or 1.e5.

Volume D contains all of the double Queen pawn openings and all openings in which 3.Nc7 Bg7 doesn't follow the opening moves 1.d4 Nf6 2.c4 g6 (that's what the parentheses mean in the list above: that those moves are not played -- so, in other words, it's the 1.d4 Nf6 2.c4 openings in which 2...g6 is played, but 3.Nc3 Bg7 doesn't follow).

4.	Volume E has the openings in which either 2...e6 or 2...g6 3.Nc3 Bg7 follow 1.d4 Nf6 2.c4.

5.	Volume A contains everything that doesn't fall into the categories of the other four volumes (stuff like the English and the various flank openings).