Frequently asked questions

Open the analysis board, go to the Import tab, paste your PGN and press Load PGN, then press Analyze Game. Stockfish checks every move and a progress bar shows how far it is. When it is done, the Review tab opens with accuracy, a graph and a summary of your moves. Analysis is free.

Use the analysis option on the game-over screen: your game opens in the analysis board and is analyzed automatically. Older games can be opened from the game history on your profile.

Open the analysis board, switch to the Export tab and press Copy PGN. The PGN is the text record of all moves, so you can paste it into another chess app, save it or send it to a friend. Copy FEN copies only the current position.

On the Import tab, paste the PGN and press Load PGN, or paste a FEN and press Load FEN. You can export PGN files from most chess sites and apps. If the text is not a valid PGN, you get a message and nothing is loaded.

Stockfish evaluates every position: a positive number favours White, a negative number favours Black, and the larger the number, the bigger the advantage. Accuracy shows how close your moves were to the engine's best moves; higher is better, and each player gets their own value.

Genius, Great and Best mark very strong moves, up to the engine's first choice. Excellent and Good are solid moves that lose little or nothing. Book is a known opening move. Inaccuracy, Mistake and Blunder mark growing losses, from a small slip to a serious error. Miss means you let a good chance pass.

Press Start Review and the board jumps to your first inaccuracy, mistake or blunder, so you can see what went wrong and what the engine suggests instead. If there are no such moves, you get a message that the game was clean.

Depth sets how many moves ahead the engine looks, from 8 to 22 (default 16). A higher depth gives a more reliable evaluation but takes longer; a lower depth is faster.

No. As a guest you can play casual games and play against the computer. Ranked games need a free account, so your rating and games are saved.

In a game against the computer, Back undoes your last move and Start restarts the game from the starting position. In a game against another player the buttons only let you look at earlier positions; they never change the game.

A game is drawn by stalemate, by threefold repetition, by the fifty-move rule, when neither side has enough material to checkmate, or when both players agree to a draw.

Log in, open the Tournaments page and choose a name, time control, number of players (4 to 32) and the format, Swiss or Round Robin. Creating and playing is free.

On the Puzzles page you can solve free puzzles at your own level, and a new daily puzzle is available.

In your settings you can export your data and permanently delete your account at any time.