The Encyclopaedia of Chess Openings (ECO) is a classification system for the opening moves in a game of chess. It is presented as a five-volume book collection (now also a computer database) describing chess openings. The moves were taken from hundreds of thousands of games between masters, from published analysis in the Chess Informant since 1966, and then compiled by notable chess players. The main editor is Aleksandar Matanović. Both the ECO and the Chess Informant are published by the Serbian company Šahovski Informator (Chess Informant). These openings are typically provided in an ECO table that concisely presents the best opening lines.
The books contain only a small amount of text, which is in eight languages. The bulk of the book consists of diagrams of positions and chess moves in International figurine algebraic notation, with special symbols for comments about moves (see Chess annotation symbols).
Instead of the traditional names for the openings, ECO has developed a unique coding system that has also been adopted by other chess publications. There are five main categories, “A” to “E”, each of which is divided into one hundred sub-categories.
ECO code is a trademark of Chess Informant Inc.
|This article uses algebraic notation to describe chess moves.|
 Openings covered
 Volume A: Flank openings
- English Opening
- Benoni Defense
- Dutch Defence
- Réti Opening
- Benko Gambit
- Old Indian Defense
- Bird’s Opening
- Irregular openings, etc.
 Volume B: Semi-Open Games other than the French Defense
- Sicilian Defence
- Caro-Kann Defence
- Pirc Defence
- Alekhine’s Defence
- Modern Defense
- Scandinavian Defense, etc.
 Volume C: Open Games and the French Defense
- Ruy Lopez
- French Defence
- Petrov’s Defence
- King’s Gambit
- Philidor Defence
- Italian (Giuoco Piano, Evans Gambit, and Two Knights)
- Scotch Game
- Four Knights Game, etc.
 Volume D: Closed Games and Semi-Closed Games
- (including Grünfeld Defence but not other Indian Defenses)
- Queen’s Gambit
- Grünfeld Defence
- Queen’s Pawn Game, etc.
 Volume E: Indian Defenses
- (other than Grünfeld Defence and Old Indian Defense)
- Nimzo-Indian Defence
- Queen’s Indian Defense
- King’s Indian Defence
- Catalan Opening
- Bogo-Indian Defence, etc.
 Main ECO codes
- White first moves other than 1.e4, 1.d4 (A00–A39)
- 1.d4 without 1…d5, 1…Nf6: Atypical replies to 1.d4 (A40–A44)
- 1.d4 Nf6 without 2.c4: Atypical replies to 1…Nf6 (A45–A49)
- 1.d4 Nf6 2.c4 without 2…e6, 2…g6: Atypical Indian systems (A50–A79)
- 1.d4 f5: Dutch Defence (A80–A99)
- 1.e4 without 1…c5, 1…e6, 1…e5 (B00–B09)
- 1.e4 c6: Caro-Kann Defence (B10–B19)
- 1.e4 c5: Sicilian Defence (B20–B99)
- 1.d4 Nf6 2.c4 e6: Indian systems with …e6 (E00–E59)
- 1.d4 Nf6 2.c4 g6 without 3…d5: Indian systems with …g6 (except Grünfeld) (E60–E99)
 First edition
The first edition was published in the following years:
- Volume A: 1979
- Volume B: 1975
- Volume C: 1974
- Volume D: 1976
- Volume E: 1978
 Second edition
The second edition was published in the following years:
- Volume A: 1996
- Volume B: 1984
- Volume C: 1981
- Volume D: 1987
- Volume E: 1991
 See also
- Chess annotation symbols (ECO uses a lot of symbols instead of text)
- Chess Informant
- List of chess books
- List of chess openings for the full ECO codes
- Opening book
- Matanović, Aleksandar; Molorović, Milivoje; Božić, Aleksandar (1971). Classification of Chess Openings. Chess Informant.
- Abramov, Lev; Bagirov, Vladimir; Botvinnik, Mikhail; Cvetkovic, Srdan; Filip, Miroslav; Geller, Efim; Gipslis, Aivars; Gufeld, Eduard; Hort, Vlastimil; Kasparov, Garry; Korchnoi, Viktor; Krnic, Zdenko; Larsen, Bent; Matanović, Aleksandar; Minev, Nikolay; Nunn, John; Parma, Bruno; Polugaevsky, Lev; Suetin, Alexey; Sveshnikov, Evgeny; Taimanov, Mark; Ugrinovic, Dragan; Uhlmann, Wolfgang (1984). Encyclopedia of Chess Openings, volume B (2nd ed.). Belgrade: Chess Informant. ISBN 0-7134-3716-2.
- Publisher website. “Encyclopaedia of Chess Openings”. http://www.chessinformant.rs/categories/ECO-%252d-Encyclopeadia-of-Chess-Openings/.
- Publisher website. “ECO codes”. http://https:www.chessinformant.rs/content/eco/index.html.
- Bill Wall. “ECO codes with names”. Archived from the original on 2010-02-20. http://www.webcitation.org/query?url=http://www.geocities.com/siliconvalley/lab/7378/eco.htm&date=2010-02-20+10:14:24.
- World Correspondence Chess Federation. “ECO codes with names”. http://www.ewccf.com/eco.htm.
- website Chess Archaeology. “ECO codes with names”. http://www.chessarch.com/library/0000_eco/index.shtml.
- Complete List of Chess Openings Sorted by ECO Code.
- Searchable Database of ECO Openings
This article uses material from the Wikipedia article Encyclopaedia of Chess Openings, which is released under the Creative Commons Attribution-Share-Alike License 3.0.