Free Online Chess – Play Chess vs Computer

Choose a level and start. Beginner looks only a couple of moves ahead and will miss things; Maximum thinks for several seconds and calculates properly. Every level obeys the same rules — the weaker ones are weaker because they see less, never because they are allowed to cheat.

You can play White or Black, take a move back, flip the board, and resign a lost position. Your win, draw and loss record is kept per level in this browser.

Chess is played by two players on an eight-by-eight board. White moves first, then the players alternate. The aim is checkmate: attacking the enemy king so that it cannot escape capture on the next move. A game can also end in a draw in several ways.

• Pawn — forward one square, or two on its first move. It captures diagonally forward, which is the only piece that moves and captures differently.
• Knight — an L-shape: two squares one way and one square across. It is the only piece that jumps over others.
• Bishop — any distance diagonally. Each bishop stays on its starting colour for the whole game.
• Rook — any distance along a rank or file.
• Queen — any distance in any straight line, so it moves like a rook and a bishop combined.
• King — one square in any direction, and it may never move into check.

Castling moves the king two squares towards a rook, and the rook hops to the far side of it. It is allowed only when the king and that rook have both never moved, the squares between them are empty, the king is not currently in check, and the king neither passes through nor lands on a square the opponent attacks. The rook may be attacked, and on the queen’s side the square beside the rook only has to be empty.

When a pawn moves two squares and lands beside an enemy pawn, that pawn may capture it as though it had only moved one — but only immediately, on the very next move. Miss the chance and it is gone.

A pawn reaching the far end of the board becomes any piece you choose except a king. A queen is usually best, but not always: promoting to a knight can deliver a check a queen cannot, and occasionally a rook avoids stalemating your opponent. Zerdly always asks rather than assuming a queen.

Your king is in check when it is attacked; you must answer it immediately by moving the king, capturing the attacker or blocking the line. Checkmate is check with no legal answer, and it ends the game.

Stalemate is the opposite trap: the player to move has no legal move at all but is not in check. That is a draw, however far ahead the other player is — one of the most common ways a winning position is thrown away.

Besides stalemate, a game is drawn by threefold repetition (the same position occurs three times with the same player to move), by the fifty-move rule (fifty moves by each side with no capture and no pawn move), when neither side has enough material to force mate, or by agreement. Zerdly detects all of these automatically.

Switch to Analysis Board to explore a position freely. Paste a FEN to load a position, play any legal moves for either side, and press Analyse to see the engine’s evaluation and the line it expects. A positive number favours White, a negative one favours Black, and the units are pawns — so +1.0 means roughly a pawn ahead.

The analysis never uses the opening book, so early positions get the engine’s real assessment rather than a memorised reply. You can copy the position as FEN or the whole game as PGN at any time.

Is Zerdly Chess free?

Yes, completely, and there is no account. Choose a difficulty and start playing — nothing to install and nothing to sign up for.

How strong is the computer?

There are six levels, from Beginner up to Maximum. Every level plays by exactly the same rules and never cheats; what changes is how far ahead it looks, how long it thinks, and how finely it can tell a good move from a slightly worse one. Maximum thinks for several seconds a move and will punish loose play. We do not quote a rating, because the engine has never been formally rated and its strength depends on how fast your device is.

Does the computer ever break the rules to win?

No. Every level uses the same rule engine and the same move generator, which is verified against the standard test positions used by chess programmers. The easier levels are weaker because they look less far ahead, not because they are allowed to do anything you cannot.

Can I play a friend on the same device?

Yes. Choose Two Players and the board simply passes the turn between White and Black. Use Flip board if you would rather turn the board around between moves.

How do I move a piece?

Tap or click the piece, then tap or click where you want it to go. Legal destinations appear as dots, and squares where you can capture are ringed. You can drag pieces on a desktop if you prefer, but you never have to.

What is the analysis board for?

It lets you set up any position — paste a FEN, or just move the pieces — and ask the engine what it thinks. It shows an evaluation in pawns, or a mate if it finds one, along with the line it expects. It never uses the opening book, so you get the engine's actual opinion.

Is anything uploaded?

No. The rules, the computer opponent and the analysis all run on your device, inside your browser. Your games and your win record are stored in this browser only, and there is no account and no server to send them to.

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