The ''Encyclopaedia of Chess Openings'' (''ECO'') is a reference work describing the state of opening theory in

chess Chess is a board game for two players. It is an abstract strategy game that involves Perfect information, no hidden information and no elements of game of chance, chance. It is played on a square chessboard, board consisting of 64 squares arran ...

, originally published in five volumes from 1974 to 1979 by the Yugoslavian company Šahovski Informator (

Chess Informant Chess Informant () is a publishing company from Belgrade, Serbia, that periodically (since 2012, four volumes per year) produces volumes of a book entitled ''Chess Informant'', as well as the ''Encyclopaedia of Chess Openings'', ''Encyclopaedia ...

). It is currently undergoing its fifth edition. ''ECO'' may also refer to the opening classification system used by the encyclopedia.

Overview

Both ''ECO'' and ''

'' are published by the

Belgrade Belgrade is the Capital city, capital and List of cities in Serbia, largest city of Serbia. It is located at the confluence of the Sava and Danube rivers and at the crossroads of the Pannonian Basin, Pannonian Plain and the Balkan Peninsula. T ...

-based company Šahovski Informator. The moves are taken from thousands of master games and from published analysis in ''Informant'' and compiled by the editors, most of whom are grandmasters, who select the lines which they consider most relevant or critical. The chief editor since the first edition has been

Aleksandar Matanović Aleksandar Matanović (; 23 May 1930 – 9 August 2023) was a Serbian chess grandmaster, one of the leading Yugoslav players in the 1950s-1970s. In 1966 he founded the company Chess Informant, which publishes regular game collections from recen ...

(1930-2023). The openings are provided in an ''ECO'' table that concisely presents the opening lines considered most critical by the editors. ''ECO'' covers the openings in more detail than rival single volume publications such as ''

Modern Chess Openings ''Modern Chess Openings'' (usually called ) is a reference book on chess openings, first published in 1911 by the British players Richard Griffith (chess player), Richard Clewin Griffith (1872–1955) and John Herbert White (1880–1920). The fif ...

'' and '' Nunn's Chess Openings'', but in less detail than specialized opening books. The books are intended for an international audience and contain only a small amount of text, which is in several languages. The bulk of the content consists of diagrams of positions and chess moves, annotated with

symbols A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise different concep ...

, many of them developed by Chess Informant.

pioneered the use of Figurine Algebraic Notation to avoid the use of initials for the names of the pieces, which vary between languages. Instead of the traditional names for the openings, ''ECO'' has developed a coding system that has also been adopted by other chess publications. There are five main categories, "A" to "E", corresponding to the five volumes of the earlier editions, each of which is further subdivided into 100 subcategories, for a total of 500 codes. The term "''ECO''" is often used as a shorthand for this coding system. ''ECO'' code is a registered trademark of

Openings covered

Volume A:
Flank opening A flank opening is a chess opening played by White and typified by play on one or both (the portion of the chessboard outside the central d- and e-). White often plays in hypermodern style, attacking the from the flanks with rather than occupyi ...
s

English Opening The English Opening is a chess opening that begins with the move: : 1. c4 A flank opening, it is the fourth most popular and, according to various databases, one of the four most successful of White's twenty possible first moves. White begins ...

Benoni Defence The Benoni Defense, or simply the Benoni, is a chess opening characterized by an early reply of ...c5 against White's opening move 1.d4. The original form of the Benoni, now known as the Old Benoni, is characterized by : 1. b:Chess Opening Theor ...

Dutch Defence The Dutch Defence is a chess opening characterised by the moves: : 1. d4 f5 Black's 1...f5 stakes a claim to the e4-square and envisions an attack in the middlegame on White's ; however, it also weakens Black's kingside to some extent, espec ...

Réti Opening The Réti Opening is a hypermodern chess opening whose "traditional" or "classic method" begins with the moves: : 1. Nf3 d5 : 2. c4 White attacks Black's pawn from the , which may occasion 2...dxc4. White may couple this plan with a fian ...

Benko Gambit The Benko Gambit (or Volga Gambit) is a chess opening characterised by the move 3...b5 in the Benoni Defence arising after: :1. b:Chess Opening Theory/1. d4, d4 b:Chess Opening Theory/1. d4/1...Nf6, Nf6 :2. b:Chess Opening Theory/1. d4/1...Nf6/2. ...

Old Indian Defence The Old Indian Defense is a chess opening defined by the moves: :1. d4 Nf6 :2. c4 d6 This opening is distinguished from the King's Indian Defense in that Black develops their on e7 rather than by fianchetto on g7. Mikhail Chigorin pionee ...

Bird's Opening Bird's Opening (or the Dutch Attack) is a chess opening characterised by the move: : 1. f4 Named after 19th century English player Henry Bird, Bird's opening is a standard flank opening. White's strategic ideas involve control of the e5-squa ...

* Anti- Indian systems (

Trompowsky Attack The Trompowsky Attack is a chess opening that begins with the moves: : 1. d4 Nf6 : 2. Bg5 White prepares to exchange the bishop for Black's knight, inflicting doubled pawns upon Black in the process. This is not a lethal threat; Black can ...

Torre Attack The Torre Attack is a chess opening characterized by the moves: :1. d4 Nf6 :2. Nf3 e6 :3. Bg5 ('' ECO'' code A46) or the Tartakower Variation in the Queen's Pawn Game (''ECO'' code D03): :2... d5 :3. Bg5 or the Torre Attack in the East ...

Richter–Veresov Attack The Richter–Veresov Attack (or Veresov Opening) is a chess opening that begins with the moves: :1. d4 d5 :2. Nc3 Nf6 :3. Bg5 It is also often reached by transposition, for example 1.d4 Nf6 2.Nc3 d5 3.Bg5 (the most common move order), 1.d ...

) * Irregular openings, etc.

Volume B:
Semi-Open Game A Semi-Open Game is a chess opening in which White plays 1.e4 and Black breaks symmetry immediately by replying with a move other than 1...e5. Hooper & Whyld (1996), p. 365. ''semi-open game''. The Semi-Open Games are also called Single King Pawn, ...
s other than the French Defence

Sicilian Defence The Sicilian Defence is a chess opening that begins with the following moves: :1. e4 c5 The Sicilian is the most popular and best-scoring response to White's first move 1.e4. The opening 1.d4 is a statistically more successful opening for Whi ...

* Caro-Kann Defence *

Pirc Defence The Pirc Defence ( ) is a chess opening characterised by the response of Black to 1.e4 with 1...d6 and 2...Nf6, followed by ...g6 and ...Bg7, while allowing White to establish a with pawns on d4 and e4. It is named after the Slovenian grandmaste ...

Alekhine's Defence Alekhine's Defence is a chess opening that begins with the moves: :1. e4 Nf6 Black tempts White's pawns forward to form a broad , with plans to undermine and attack the white structure later in the spirit of hypermodern defence. White's imposi ...

Modern Defence The Modern Defense (also known as the Robatsch Defence after Karl Robatsch) is a Hypermodern chess, hypermodern chess opening in which Black allows White to occupy the with pawns on d4 and e4, then proceeds to attack and undermine this "ideal" c ...

* Scandinavian Defence, etc.

Volume C:
Open Game An Open Game (or Double King's Pawn Opening) is a generic term for a family of chess openings beginning with the moves: :1. b:Chess Opening Theory/1. e4, e4 b:Chess Opening Theory/1. e4/1...e5, e5 White has moved the king's pawn two squares and Bl ...
s and the French Defence

Ruy Lopez The Ruy Lopez (; ), also called the Spanish Opening or Spanish Game, is a chess opening characterised by the moves: :1. e4 e5 :2. Nf3 Nc6 :3. Bb5 The Ruy Lopez remains one of the most popular chess openings, featuring many variations. In ...

French Defence The French Defence is a chess opening characterised by the moves: :1. e4 e6 This is most commonly followed by 2.d4 d5. Black usually plays ...c5 soon after, attacking White's and gaining on the . The French has a reputation for solidity ...

Petrov's Defence Petrov's Defence or the Petrov Defence (also called Petroff Defence, Petrov's Game, Russian Defence, or Russian Game ">/nowiki> is a chess opening characterised by the following moves: :1. e4 e5 :2. Nf3 Nf6 Though this response has a long ...

Vienna Game The Vienna Game is an opening in chess that begins with the moves: :1. e4 e5 :2. Nc3 White's second move is less common than 2.Nf3, and is also more recent. The original idea behind the Vienna Game was to play a delayed King's Gambit with f ...

* Centre Game *

King's Gambit The King's Gambit is a chess opening that begins with the moves: :1. e4 e5 :2. f4 White offers a pawn to divert the black e-pawn. If Black accepts the gambit, White may play d4 and Bxf4, regaining the gambit pawn with domination, or direc ...

Philidor Defence The Philidor Defence (or Philidor's Defence) is a chess opening characterised by the moves: :1. e4 e5 :2. Nf3 d6 The opening is named after the famous 18th-century player François-André Danican Philidor, who advocated it as an alternativ ...

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, a Romance ethnic group related to or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance languag ...

(

Giuoco Piano The (; )Hooper & Whyld (1996), p. 153. ''Giuoco Piano''. "The name means 'quiet game' and until the 19th century was often applied to any opening that was not a gambit." is a chess opening beginning with the moves: :1. e4 e5 :2. Nf3 Nc6 :3. ...

Evans Gambit The Evans Gambit is a chess opening characterised by the moves: :1. e4 e5 :2. Nf3 Nc6 :3. Bc4 Bc5 :4. b4 The Evans Gambit is an attacking line of the Giuoco Piano. White offers a pawn to divert the black bishop on c5. If Black accepts, W ...

, Hungarian Defence, and Two Knights) * Scotch Game *

Four Knights Game The Four Knights Game is a chess opening that begins with the moves: :1. e4 e5 :2. Nf3 Nc6 :3. Nc3 Nf6 This is the most common sequence, but the knights may in any order to reach the same position. The Four Knights usually leads to quiet ...

, etc. * King's Pawn Opening, etc. (covers unusual/rare 1. e4 openings such as the

Elephant Gambit The Elephant Gambit (also called the Queen's Pawn Countergambit, Englund Counterattack or Turkish Gambit) is a rarely played chess opening beginning with the moves: :1. e4 e5 :2. Nf3 d5 The Elephant Gambit is generally considered unsound, wi ...

and

Ponziani Opening The Ponziani Opening is a chess opening that begins with the moves: :1. b:Chess Opening Theory/1. e4, e4 b:Chess Opening Theory/1. e4/1...e5, e5 :2. b:Chess Opening Theory/1. e4/1...e5/2. Nf3, Nf3 b:Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc ...

Volume D: Closed Games and
Semi-Closed Game A Semi-Closed Game (or Semi-Closed Opening) is a chess opening in which White plays 1.d4 but Black does not make the symmetrical reply 1...d5.Hooper & Whyld (1996), p. 365. ''semi-close game''. (The openings starting 1.d4 d5 are the Closed Games.) ...
s

:(''including Grünfeld Defence but not other Indian Defenses'') *

Queen's Gambit The Queen's Gambit is the chess opening that starts with the moves: :1. d4 d5 :2. c4 It is one of the oldest openings and is still commonly played today. It is traditionally described as a '' gambit'' because White appears to sacrifice the ...

** Accepted ** Declined (

Slav The Slavs or Slavic people are groups of people who speak Slavic languages. Slavs are geographically distributed throughout the northern parts of Eurasia; they predominantly inhabit Central Europe, Eastern Europe, Southeastern Europe, and N ...

, Orthodox, Tarrasch, Tartakower,

Albin Countergambit The Albin Countergambit is a chess opening that begins with the moves: :1. d4 d5 :2. c4 e5 and the usual continuation is: :3. dxe5 d4 The opening is a gambit and an uncommon response to the Queen's Gambit. In exchange for the sacrificed ...

, etc.) *

Grünfeld Defence The Grünfeld Defence is a chess opening characterised by the moves: :1. d4 Nf6 :2. c4 g6 :3. Nc3 d5 Black offers White the possibility of 4.cxd5, which may be followed by 4...Nxd5 and 5.e4, giving White an imposing duo. If White does not ...

Queen's Pawn Game The Queen's Pawn Game is any chess opening starting with the move: : 1. d4 It is the second-most popular opening move after 1.e4 (King's Pawn Game). Terminology The term "Queen's Pawn Game" is usually used to describe openings beginning wit ...

, etc.

Volume E:
Indian Defence In the game of chess, Indian Defence or Indian Game is a broad term for a group of chess opening, openings characterised by the moves: : 1. b:Chess Opening Theory/1. d4, d4 b:Chess Opening Theory/1. d4/1...Nf6, Nf6 They are all to varying degrees ...
s

:(''other than Grünfeld Defence and Old Indian Defence'') *

Nimzo-Indian Defence The Nimzo-Indian Defence is a chess opening characterised by the moves: :1. d4 Nf6 :2. c4 e6 :3. Nc3 Bb4 Other move orders, such as 1.c4 e6 2.Nc3 Nf6 3.d4 Bb4, are also feasible. In the ''Encyclopaedia of Chess Openings'', the Nimzo-Indian ...

Queen's Indian Defence The Queen's Indian Defense (QID) is a chess opening defined by the moves: : 1. b:Chess Opening Theory/1. d4, d4 b:Chess Opening Theory/1. d4/1...Nf6, Nf6 : 2. b:Chess Opening Theory/1. d4/1...Nf6/2. c4, c4 b:Chess Opening Theory/1. d4/1...Nf6/2. c ...

King's Indian Defence The King's Indian Defence (or KID) is a common chess opening. It is defined by the following moves: : 1. d4 Nf6 : 2. c4 g6 Black intends to follow up with 3...Bg7 and 4...d6 (the Grünfeld Defence arises when Black plays 3...d5 instead and ...

Catalan Opening The Catalan Opening is a chess opening where White plays d4 and c4 and fianchettoes the white bishop on g2. A common opening sequence is 1.d4 Nf6 2.c4 e6 3.g3, although various other openings can transpose into the Catalan. The ''Encyclopaedia of ...

Bogo-Indian Defence The Bogo-Indian Defence is a chess opening characterised by the moves: :1. d4 Nf6 :2. c4 e6 :3. Nf3 Bb4+ The position after 1.d4 Nf6 2.c4 e6 is common. The traditional move for White here is 3.Nc3, threatening to set up a big pawn centre wi ...

, etc.

Main ''ECO'' codes

A

* White first moves other than 1.e4, 1.d4 (A00–A39) * 1.d4 without 1...d5, 1...Nf6 or 1...f5: 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:

(A80–A99)

B

* 1.e4 without 1...c6, 1...c5, 1...e6, 1...e5 (B00–B09) * 1.e4 c6: Caro–Kann Defence (B10–B19) * 1.e4 c5:

(B20–B99)

C

* 1.e4 e6:

(C00–C19) * 1.e4 e5: Double King Pawn games (C20–C99)

D

* 1.d4 d5: Double Queen Pawn games (D00–D69) * 1.d4 Nf6 2.c4 g6 with 3...d5:

(D70–D99)

E

* 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

Third edition

The third edition was published in the following years: * Volume A: 1999 * Volume B: 1997 * Volume C: 1997 * Volume D: 1998 * Volume E: 1998

Fourth edition

The fourth edition was published in the following years: * Volume A: 2001 * Volume B: 2002 * Volume C: 2000 * Volume D: 2004 * Volume E: 2008

Fifth edition

The fifth edition was published in the following years: * Volume C: 2006 * Volume B part 1 CO codes: B00–B49 2020 * Volume B part 2 CO codes: B50-B99 2021

References

Bibliography * * *

External links

* Publisher's site * ''ECO'' codes with names {{Chess, state=collapsed *Encyclopedia of Chess Openings Chess books Chess in Yugoslavia Chess in Serbia 20th-century encyclopedias