How to play
- Moving: tap a piece, then tap where it should go. You can also drag it. The dots show every square it can reach; a ring means a capture.
- Castling: move your king two squares toward the rook, and the rook jumps over.
- Promotion: when a pawn reaches the far side, pick the piece it becomes.
- Looking back: tap any move in the list, or use the ◀ ▶ buttons (or the arrow keys) to step through the game. The board goes back to the game when you press ⏭.
- Keyboard: Tab onto the board, move around with the arrow keys, and press Enter to pick up and put down a piece.
Three ways to play
Against the computer. Level 1, the Duckling, is a simple bot that only just learned the rules: good for a first game. Levels 2 to 8 are Stockfish, one of the strongest chess programs in the world, turned down to play like a beginner, a club player, an expert and finally at full strength. You can undo moves and ask for a hint. Your record at each level is kept on this device.
Pass and play. Two people share one screen. Pick a clock if you want one; it starts after Black’s first move, and the board can turn round after every move so each player sees it from their side.
Online with a friend. Create a room and send the link (or the four-letter code). Choose the clock and who plays White, then start. If your connection drops, you have two minutes to come back to your seat. Colors swap every rematch, and anyone else who opens the link can watch.
Analyzing your game
When a game ends, press Analyze game. Stockfish looks at every position (about half a second each) and marks each move that cost you: ?! an inaccuracy, ? a mistake, ?? a blunder. Step through the moves to see the evaluation (plus means White is better, M3 means mate in 3), what you should have played instead, and the best move in each position, shown in blue on the board. The graph shows how the game swung; tap it to jump to that moment. Avg loss is how much each player’s moves fell short of the engine’s, on average, in hundredths of a pawn: lower is better.
Questions
Is it free? Yes. No account, no download, nothing to pay for.
Where does the computer think? In your browser. Stockfish runs on your own device, so the computer still plays if your connection drops, and the first game needs a one-time 7 MB download.
Which level should I pick? If you’re new to chess, start at 1 or 2. Most casual players find level 3 or 4 a fair game. Level 8 beats every human.
Does it know all the rules? Yes: castling, en passant, promotion, checkmate and stalemate, and the draws by repetition, the fifty-move rule and too few pieces to checkmate.
Can I save a game? Games against the computer and pass-and-play games are saved on this device, so you can close the page and carry on later. When a game ends, Copy moves (PGN) copies it in the standard format that other chess sites and apps can open.