It finds the best move in any chess position. Set up the board and choose who is to move, and Stockfish shows the best move as a green arrow, with the square to move to highlighted.

Drag pieces anywhere on the board. Add pieces from the trays above and below it, and drag a piece off the board to remove it. ‘Kings only’ clears the board, and ‘Reset board’ restores the starting position.

Press ‘Upload screenshot’. On a computer, you can also drag the image onto the page or paste it with Ctrl+V. The board copies the position and turns to match it. Check that it is right, and drag any wrong pieces into place. We don't store your screenshots or positions.

They choose whose turn it is. The engine always finds the best move for the side to move, and the turn switches automatically after each normal move.

Drag the king two squares towards the rook, or drop it onto its own rook. Castling only works when the rules allow it, and if it doesn't, a message explains why.

It plays the suggested move on the board for you, so you can follow the engine’s line one move at a time. On a phone, a ‘Play best move’ bar appears at the bottom of the screen whenever the button itself is out of view.

On a computer, ‘Pop out’ under the board opens the board in its own small window, so you can keep it open while you use other websites. It has the pieces, the best move, ‘Play best move’ and its own back and forward buttons, and it uses the same theme as the main page. In Chrome and Edge, the window floats on top of everything else, even when you click on other apps or websites. Other browsers open it as an ordinary window that you can place beside them. The moves you play there appear in the main page’s move list straight away. To bring the board back, close the small window or press ‘Bring it back here’.

Green is the suggested move: the arrow shows the move and the green square is where to go. A light wood tint shows the last move made, and a darker one shows the piece you have selected, with dots where it can go. Red shows a king in check, and the squares and arrows you mark yourself.

They show who is better, measured in pawns. A plus sign means White is better and a minus sign means Black is better, so +1.50 means White is about one and a half pawns ahead. +M3 means White can force checkmate in three moves. The bar beside the board shows the same score.

Select the piece by clicking or tapping it. The green arrow and square switch to that piece's best move, and the panel shows the move and its score. Select it again, or click an empty square, to go back to the best move on the whole board.

Yes. Right-click a square to highlight it in red, or right-click and drag between two squares to draw a red arrow. Left-click the board to clear them.

Yes. Use the arrow buttons above the move list, or click any move to jump straight to that position. The list also logs the changes you make to the board, such as adding a piece, loading a screenshot or switching who is to move, so you can step back through those too.

They're in the ‘Settings’ panel beside the board, or below it on phones. Use the link below to jump there. The panel will flash so it's easy to spot, and you can click it to open the settings.
Take me to the settings ↑

It sets how long Stockfish thinks: 0.5 seconds on Low, 3 on Medium, 10 on High and 20 on Max. The longer it thinks, the stronger the move. A move appears almost straight away and keeps improving while the green line fills up.

It shows the engine's top one, two or three moves, both as arrows and in the list beside the board. The best move has the thickest arrow, the second-best a thinner one and the third-best the thinnest. Point at a move in the list to see only its arrow. Choosing 1 lets the engine focus on the best move.

It turns the move sounds on or off. When it is on, you hear a wooden tap when a piece moves, a heavier knock for a capture, a double tap for castling and a toppling king for checkmate. This includes playing the best move and stepping backwards and forwards through the moves. Buttons and switches make a quiet tick, and reading a screenshot ends with a cheerful chime if it works or a low knock if it doesn't.

‘Theme’ switches between Light, Dark and System, which follows your device's setting. ‘Coordinates’ shows or hides the square names, such as e4, around the edge of the board.

It tells the engine whether each side can still castle. O-O means castling kingside and O-O-O means castling queenside, and the white or black rook shows which side each button is for. Castling switches off automatically once the king or that rook moves. ‘Reset’ turns it back on wherever the king and rook are still on their starting squares.

‘Rotate’ turns the board so you see it from the other side. ‘Reset board’ puts every piece back in its starting position, and it glows after a checkmate to show you can start again. ‘Kings only’ clears everything except the two kings.

It uses Stockfish, one of the strongest chess engines in the world, which runs in your own browser.

Press ‘Share’ at the top of the page. On a phone, it opens your phone's share menu so you can pick any app. On a computer, choose Facebook, Reddit, WhatsApp or X to open a post with the link already added, or copy the link.

Yes. Set up the position, press ‘Share’ and choose ‘Copy position link’. Anyone who opens the link sees the same board, with the same side to move, and Stockfish shows them the best move straight away. On a phone, ‘Share’ sends the position link automatically once you have changed the board from the starting position.

Yes. It's free and works on phones, tablets and computers, with no sign-up and nothing to install.

Yes, on a computer. Press the space bar to play the best move, and the left and right arrow keys to step backwards and forwards through the moves. F rotates the board, T switches who is to move and Esc deselects a piece.

No. Use it to study your games after they finish, to solve puzzles or to prepare openings. Using an engine during a live game counts as cheating on every chess site and can get your account banned.