Online Chess Game

A chess game can end with all 32 pieces still on the board. The main objective is checkmate, not taking every opposing piece. Each turn must balance an attack on the other king with protection of your own, and the king itself is never captured.

The standard game begins on an 8 by 8 board with 16 pieces for each player. Each army has a king, a queen, two rooks, two bishops, two knights and eight pawns. White moves first, then the players alternate. Columns are called files and are labelled a to h. Rows are called ranks and are numbered 1 to 8, so a square such as e4 has the same name regardless of which player is looking at the board.

Check

The king is under attack. The next move must remove that attack without leaving the king exposed to another one.

Checkmate

The king is in check and its player has no legal response. The attacking player wins immediately.

Stalemate

The player to move has no legal move, but the king is not in check. The game is a draw, even when the opponent has many more pieces.

Piece placement matters because attacks follow different paths. A rook needs an open row or column, a bishop needs a diagonal, and a knight can jump over intervening pieces. Moving a blocker may open an attack in either direction. A piece shielding its own king is pinned when moving it would expose that king, so some otherwise ordinary moves are forbidden.

Pawns create lasting changes because they cannot move backwards. They advance straight ahead but capture diagonally, and reaching the far end of the board earns promotion to a queen, rook, bishop or knight. Castling moves a king and rook together under special conditions. En passant allows a pawn to capture an opposing pawn immediately after a particular two-square advance. Castling and en passant depend on move history as well as the visible arrangement of pieces.

A full game connects these rules across many decisions, while a small endgame makes individual ideas easier to see. A lone pawn may still become a mating piece, and a queen can accidentally leave the enemy king stalemated. Legal movement is only the starting point for a good decision. The opponent's next reply and the remaining escape squares can matter more than the piece just captured.

How to Use This Tool:

The default is an untimed two-player match from the standard position, with White at the bottom. Moves and computer choices are processed in your browser.

1. Choose Second player to share one device or Computer for a solo match. Your side sets your colour against the computer and the initial view. Playing Black lets the computer open. Choose Standard chess for a full game or a practice position for a focused exercise. Computer levels range from varied Casual moves to material-focused Balanced and one-reply Careful play.
2. Keep the suggested Replay seed or enter nonblank text of up to 80 characters, then select Start match. If starting is disabled, replace an empty or spaces-only seed. Surrounding spaces are removed when play begins.
3. Select a piece and then a highlighted destination. Click or tap the squares, or use arrow keys to move focus and Enter or Space to select. Flip board changes only the view.
   When Promote your pawn appears, choose Queen, Rook, Bishop or Knight to complete the move.
4. Review the winner or draw reason when play ends. Open Review the final position and moves to inspect the finish. Replay same seed begins again from the chosen start; it does not play the recorded moves. New seed keeps the setup, and Change setup reopens the choices.
   If a replay cannot start, try its action again or choose Change setup.

Take back revisits a decision while the match is running. Two-player play removes the last individual move. Computer play removes your move and the reply. The computer’s opening move alone cannot be taken back when you play Black, and completed matches cannot be taken back.

Interpreting Results:

Highlighted destinations are legal moves, not recommendations. A highlighted capture may still lose a piece on the next turn. If a piece will not select, check Turn and whether that piece has any legal moves. When Position shows Check, the accompanying message names the attacking pieces and their squares.

Moves and Moves played count each player's move separately. After White plays e4 and Black replies e5, the total is 2, although the move history groups both under move number 1. One such individual move is also called a halfmove or ply. Castling and promotion each count as one individual move.

Captured lists pieces taken since the selected starting position, not every piece absent from the board. A sparse practice position therefore begins with no captures recorded. The final headline gives the winner or draw, and the reason distinguishes checkmate from a draw rule or resignation.

Computer levels are unranked practice opponents, not measured ratings. A win does not establish a playing-strength rating, and match results have no monetary value.

Technical Details:

Legal movement combines a piece's movement pattern with king safety. A move cannot land on a friendly piece, capture the opposing king, or leave the moving player's king under attack. A normal capture removes an enemy piece from the destination square. En passant instead removes the adjacent pawn.

Rule Core

These movement rules apply before the king-safety restriction. Rooks, bishops and queens cannot jump over pieces.

A response to check must remove every attack on the king. Depending on the position, that may mean moving the king, capturing an attacker or blocking a line of attack. A knight's attack cannot be blocked. An enemy piece still attacks squares for king-safety purposes even when moving that piece would expose its own king.

Castling, en passant and promotion

Castling requires the king and the chosen rook to retain their castling rights, with every intervening square empty. The king cannot castle while in check, cross an attacked square or finish on one. It moves two squares towards the rook, and the rook moves to the square the king crossed. For White, kingside castling moves the king from e1 to g1 and the rook from h1 to f1. Queenside castling uses e1 to c1 and a1 to d1. Black uses the corresponding squares on rank 8. Moving a king or rook away and back does not restore its lost right.

En passant is available only on the immediate reply to an adjacent enemy pawn's two-square advance. The capturing pawn moves diagonally into the square that pawn passed over, and the advanced pawn is removed. For example, a white pawn on e5 can capture on d6 immediately after a black pawn advances from d7 to d5. The capture is forbidden if the resulting position exposes the capturing player's king.

Promotion is mandatory on the last rank: rank 8 for White or rank 1 for Black. The pawn becomes a queen, rook, bishop or knight of its own colour as part of that move, including a capturing move. The choice is not restricted to previously captured pieces, and the new piece's attacks take effect immediately.

Automatic endings and their order

After a completed move, the following conditions are checked in order. The first matching condition ends the match, so checkmate takes precedence over a draw counter reached on the same move.

Repetition compares the pieces and their squares, the player to move, castling rights and any legally available en passant capture. The occurrences need not be consecutive. Identical-looking boards can differ if castling rights have changed, while different move counters do not prevent a repetition. Pawn moves and captures reset the fifty-move count to zero.

Automatic threefold and fifty-move endings are deliberate casual rules. Tournament rules distinguish claims at three occurrences or 50 moves by each player from automatic draws at five occurrences or 75 moves by each player. Matches here end at the earlier thresholds without a claim.

The material check does not detect every dead position, meaning a position where neither player can ever deliver mate through any legal continuation. Blocked positions outside the listed material cases may continue. In two-player play, Agree draw can end any active match after confirmation that both players agree. Computer matches do not offer that agreement control.

Resign applies to the player whose turn it is in a two-player match, or to the human player against the computer. After confirmation, the opponent wins unless that opponent has only a king or the position meets the listed insufficient-material test. Those exceptions produce a draw. This resignation check is material-based, not an exhaustive test of every possible mating continuation.

Formula Core: material evaluation

Material evaluation compares the pieces remaining for each player. The computer's weighted total is reduced by its opponent's weighted total.

Each V is the sum of the remaining piece weights: pawn 100, knight 320, bishop 330, rook 500 and queen 900. Kings contribute zero to this material calculation because they are not exchangeable pieces. M is positive when the computer has more weighted material. These integer values guide move selection; they are not a displayed match score or a rating.

• Casual uses seeded variation among legal moves without preferring captures, material gains or checkmate.
• Balanced prefers the highest material balance immediately after its candidate move.
• Careful examines every legal immediate opponent reply to each candidate. It compares the worst resulting material balance for each candidate and chooses the most favourable of those worst cases.

Balanced and Careful both give an immediately delivered checkmate priority over material and treat an immediate stalemate as neutral. Careful gives no extra penalty to an opponent reply that would deliver checkmate, because its reply comparison uses material alone. Neither level searches a long tactical line or assesses a complete positional plan.

When several moves have the same preference, the seed chooses between them. The same setup, seed and player moves reproduce the same computer replies under the same rules. After a takeback, repeating the same move produces the same reply. A new seed can still produce the same reply, particularly when one move is clearly preferred, and it does not randomise the selected starting board.

Move notation and position records

Standard Algebraic Notation (SAN) records a move by its piece and destination, with extra marks for captures, promotion and check. Pawn moves omit the piece letter.

When multiple pieces of the same kind can legally reach a destination, the notation adds the starting file, rank or both to identify the mover. En passant uses ordinary pawn-capture notation without a separate suffix.

Forsyth–Edwards Notation (FEN) describes a position in six fields: piece placement, player to move, castling rights, en passant target, halfmove count and fullmove number. An en passant target can be recorded after a two-square pawn move even when no legal capture is available. FEN describes the position rather than its complete history, so it cannot by itself establish threefold repetition.

Worked Examples:

Choose Second player for these examples so the computer does not make any of the moves.

FAQ:

References:

• FIDE Laws of Chess taking effect from 1 January 2023, International Chess Federation, 2023.
• Portable Game Notation Specification and Implementation Guide, Steven J. Edwards, coordinator, 1994.