Eco Code System Explained

ECO (Encyclopedia of Chess Openings) is a unique system of classifying all main chess openings by 500 codes from A00 to E99.

The Eco Code System was invented by Chess Informant in year 1966


Example: In this Game it’s  C50: Blackburne Shilling Gambit. The Main Trap mates in 7# You can see the Eco Code in any Game with a Recognized Chess Opening.


Click on Eco Codes or Interval will to go to the Openings

Eco A (without 1. e4): Irregular Openings

  • A00-A39 Irregular Openings (neither 1.d4 nor 1.e4): includes English Opening

  • A40-A44 Queens Pawn Opening without 1..d5 or 1..f5 or 1..Nf6 reply

  • A45-A49 Queens Pawn, Indian Defence 1.d4 Nf6 without 2.c4

  • A50-A79 Queens Pawn, Indian Defence  with 2.c4 but without 2..e6 or 2..g6

  • A80-A99 Queens Pawn with 1..f5 reply (Dutch Defence)

Eco B: Semi-Open Games other than the French Defence (1. e4)

  • B00-B19 Kings Pawn without 1..c5, ..1.e6 or ..1.e5 incl. Alekhine, Caro-Kann Defence

  • B20-B99 Kings Pawn with 1..c5 reply (Sicilian Defence)

Eco C: Open Games and the French Defence (1. e4)

  • C00-C19 Kings Pawn with 1..e6 reply (French Defence)

  • C20-C99 Kings Pawn with 1..e5 reply (Mutual King’s Pawn, incl. Ruy Lopez)

Eco D: Closed Games and Semi-Closed Games (1. d4)

  • D00-D05 Queens Pawn Game 1.d4 d5 without 2.c4

  • D06-D69 Queens Pawn Game 1.d4 d5 with 2.c4 (Queen’s Gambit)

  • D70-D99 Queens Pawn Indian Defence. (1.d4 Nf6, 2.c4 g6) with early ..d5 (Gruenfeld Defence)

Eco E: Indian Defences (1. d4)

  • E00-E59 Queens Pawn Indian Defence. (1.d4 Nf6) with 2.c4 e6 includes Catalan Opening

  • E60-E99 Kings Indian Defence. (1.d4 Nf6, 2.c4 g6) without early ..d5 (King’s Indian)