Chess Opening Explorer
Chess opening encyclopedia. 50 major openings with ECO codes, main-line PGN, key ideas, typical plans. Search by name, ECO code, or starting moves.
Chess Opening Explorer
How to use
Search by name, ECO, or move
"Sicilian" lists all Sicilian variations. "B90" finds the Najdorf. "Bb5" finds openings featuring that move.
Filter by family
Use the family dropdown to narrow to "King's Pawn", "Sicilian", "Indian", "Queen's Gambit", "English", and more.
Study the main line
Each card shows the canonical move sequence in SAN. Copy and paste into the chess board tool to play it through.
Grab the FEN
Expand "FEN after main line" to get the position string — paste into engines or chess software.
Chess Opening Reference — 50 Major Openings + ECO Codes
The chess opening — the first 10-15 moves of a game — has been studied for centuries. This tool catalogues 50 of the most important openings in the modern game, organised by the ECO classification system (Encyclopaedia of Chess Openings) used universally across chess literature, databases, and engines.
The ECO classification system
The Encyclopaedia of Chess Openings, published in five volumes (A, B, C, D, E) by Šahovski Informator (Belgrade) since 1974, divides every chess opening into 500 codes:
- A00-A99: Flank openings — c4 (English), Nf3 (Réti), Dutch, Bird, plus oddballs
- B00-B99: Semi-Open Games — everything except 1.e4 e5 (Sicilian, French, Caro-Kann, Pirc, Alekhine, Scandinavian)
- C00-C99: Open Games — 1.e4 e5 (Ruy López, Italian, Scotch, King's Gambit, Petroff)
- D00-D99: Closed Games — 1.d4 d5 (Queen's Gambit, Slav, Semi-Slav)
- E00-E99: Indian Defences — 1.d4 Nf6 (Nimzo-Indian, King's Indian, Queen's Indian, Grünfeld, Catalan)
"The Sicilian Defence (1...c5) is statistically the most popular response to 1.e4 at every level from beginner online blitz to World Championship matches — about 25% of top-level games."
Why study openings?
An opening establishes the pawn structure (which dictates middlegame plans), the piece activity (which determines tactical chances), and your study workload (some openings have 30+ moves of pre-played theory). Modern grandmasters specialise in a small repertoire — 2-3 openings as White, 2-3 as Black — and know each one to 20+ moves deep.
Magnus Carlsen's anti-theory philosophy
Carlsen famously avoids deep theoretical lines, preferring offbeat "system" openings like the London System (1.d4 + 2.Bf4) and the Réti (1.Nf3). His logic: in classical chess, an extra hour of opening prep gives diminishing returns vs better middlegame skills. He demonstrated this in the 2018 World Championship vs Caruana, where 12 games of classical chess ended in 12 draws.
Singapore + ASEAN opening trends
Asian chess academies — particularly in India, Vietnam, and the Philippines — favour sharp tactical openings (Sicilian Najdorf, Open Sicilian, King's Indian). Singapore Chess Federation's youth program emphasises solid systems first (London, Caro-Kann) before transitioning students to sharper repertoires at master level. The ASEAN Chess Confederation Championships regularly produce IM-level games in all major openings.
Data sourcing
The opening names, ECO codes, and main-line moves are universal chess knowledge — no copyright applies. Move sequences are the standard "ECO mainlines" found in every chess database. The descriptions are original summaries, not copied from any commercial source.
10 Facts about Chess Openings
The ECO encyclopedia was first published in 1974 by Šahovski Informator (Belgrade, then-Yugoslavia). It remains the canonical opening reference, updated periodically through the 1990s.
The Sicilian Defence (1...c5) is statistically the most popular response to 1.e4 at every level — appearing in roughly 25% of all chess games from beginner blitz to World Championships.
The Ruy López (1561) is the oldest analysed opening still in regular use. Named after Spanish priest Ruy López de Segura, who wrote the first book on it.
The Queen's Gambit isn't actually a gambit — Black almost never keeps the pawn (it can be regained easily). It's really a positional opening fighting for the centre.
The longest opening line in MCO (Modern Chess Openings, 15th edition) is in the Sicilian Najdorf — 35 moves of analysis without leaving "theory".
Bobby Fischer's favourite was the Sicilian Najdorf (B90-B99) as Black and the Ruy López (C60-C99) as White. He memorised both to 25+ moves deep.
The London System, once dismissed as "boring", became Magnus Carlsen's pet opening in the 2010s. Both Carlsen and Caruana use it regularly in elite tournaments.
Hypermodern openings (Alekhine's Defence, Pirc, Modern) were developed in the 1920s by Réti, Nimzowitsch, and Tartakower, who challenged classical "control the centre with pawns" doctrine.
The Catalan (1.d4 Nf6 2.c4 e6 3.g3) was Vladimir Kramnik's primary weapon in his 2006 World Championship victory over Topalov. Long-term positional pressure.
The Italian Game (1.e4 e5 2.Nf3 Nc6 3.Bc4) saw a major revival in the 2010s — Caruana, Anand, and So all played it in elite events, replacing the Ruy López as the "main" 1.e4 e5 reply.
Frequently Asked Questions
ECO defines 500 codes, but that's codes — actual opening variations number in the thousands. This tool covers the 50 most common at club and master level. Specialised reference works (NCO, MCO) cover hundreds more.
For White: Italian Game (C50) or London System — solid, easy to learn, hard to refute. For Black vs e4: Caro-Kann (B10-B19); vs d4: Queen's Gambit Declined (D30-D69). Both are forgiving of inaccuracies and teach good principles.
The Sicilian Najdorf —
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6. ECO codes work like a hierarchy: A/B/C/D/E indicate the family, the first digit (0-9) narrows it, the second digit (0-9) further specifies. So B90-B99 are all Najdorf variations.Yes — every opening in this tool is in regular use at GM tournaments. Even "old" openings like the Italian Game and Ruy López have had recent theoretical breakthroughs in the 2020s. Chess opening theory never stops evolving.
A gambit sacrifices a pawn (sometimes more) for development, attacking chances, or initiative. Famous examples: King's Gambit (1.e4 e5 2.f4), Queen's Gambit (1.d4 d5 2.c4 — though Black usually declines), Evans Gambit (4.b4 in the Italian Game).
Both start with
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3. Najdorf continues 5...a6 (flexibility, prepare e5 or e6). Dragon continues 5...g6 (kingside fianchetto, leading to opposite-side castling and razor-sharp attacks).The dataset is hard-coded in the tool's app.js — feature requests welcome via the tool request form. The data format is simple JSON-like array, easy to extend.
For scope — 500 ECO codes × 5-10 subvariations each = thousands of lines. Specialised opening databases (Chess Tempo, Lichess Opening Explorer, ChessBase) are better for deep theoretical research. This tool gets you to the right family quickly.
Original summaries based on universally-acknowledged chess history. The opening names and main moves are universal (no copyright). The descriptions are written specifically for this tool — short overviews of key strategic ideas and historical context.
Books: Modern Chess Openings (MCO-15), Fundamental Chess Openings (FCO). Online: Lichess Opening Explorer (free, position-aware database), ChessBase / Chess.com (paid, extensive). Video: GM Daniel Naroditsky's YouTube speedruns, ChessNetwork lectures.
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