Ground truth agreesYou played Qg8+
Ground truth · Stockfishmate in 2
Chess puzzles with two answers. Pick the best move.
White to move
Play the tenTwo candidates. Choosing one inks it on the diagram and asks how sure you are; you can still switch.
White to moveRated 1564 on Lichess
How sure are you?
At 50% you are claiming nothing at all. That is a coin flip, and it would be scored as one.
At 65% you are claiming you would be wrong about once in every 3 calls like this one.
At 80% you are claiming you would be wrong about once in every 5 calls like this one.
At 95% you are claiming you would be wrong about once in every 20 calls like this one. The scale stops at 99%, because we do not offer 100%.
Pick a move first — tap A or B on the board.
Now say how sure you are — one of the four keys above.
Recorded from the moment this page opens, with no name attached: what this page records.
02 / the reading
The reading
JavaScript is off, so both outcomes are printed below, exactly as they sit in this page.
Make the call above and this fills in. Until then it is empty on purpose — an instrument with no reading on it should look like an instrument with no reading on it.
Ground truth disagreesYou played Nf7+
Ground truth · Stockfish-641 against mate in 2
Ten puzzles is about two minutes, and Stockfish has already scored every move in the deck.
03 / why it loses
Why the move you picked loses.
Every trainer shows you the best move. This one shows you what your move does — the whole line, move by move, on a board you can step through.
Stockfish checked every line before it went on the page. Anything it would not confirm was thrown out, not fixed up.
Nf7+ only trades down to level material on f1. Qg8+ is guarded by a knight, so Black must give back the rook — and the king has nowhere left to run, mate next move.
Nf7+ — the move that loses, played out
- Nf7+You throw a knight in with check, forking the king and the queen in one move.
- Rxf7Black takes the knight with the rook — but that rook is standing right where White's queen can take it back.
- Qxf7White recaptures with the queen, coming out a rook for a knight ahead — but the attack has stopped, and the queen is standing alone on the kingside.
- Nxf1The knight that had been forking the queen all along now scoops up the rook on f1 instead.
- Kxf1White's own king has to step in and take it back on f1, leaving the material level and no attack left at all.
Qg8+ — the move that wins, played out
- Qg8+You push the queen to g8, giving check — and because a knight is guarding that square, the king can't capture it.
- Rxg8Black has to recapture with the rook — and that rook, together with the bishop and pawn already there, walls the king in completely.
- Nf7#Now the other knight jumps into f7 with check, and the king has nowhere to go — it's boxed in by its own rook, bishop, and pawn, and that's mate.
04 / what we will not say
We are not going to tell you how good at chess you are.
Not from one move. Every other chess test asks how strong you think you are and then believes the answer. This one watches which move you actually play and scores it against something that cannot be flattered: an engine that has already searched the position.
Calibration — how close the confidence you state sits to how often you turn out to be right — is the number this site is named after, and it takes about twenty decisions. Ten is not twenty, so the card at the end prints the score, prints what each move you missed cost, and says how many decisions calibration is still short of.
05 / begin
Ten positions, two moves on each. Start the set.
Ten positions, ten confidence readings, about two minutes. At the end you get how many you played best, what the ones you missed cost, and a card that says what it is still waiting for.
No account, no email, no cookie banner, no third-party analytics. Your history is stored in this browser and no copy of it is sent anywhere. What is written down is on the notice, and it is written as you go.