Best move finder
Paste a position and get one move back, with the evaluation and the line that follows. For stepping through a whole game, use the analysis board instead.
What this can and cannot tell you
A best move is an answer about one position. It is reliable for forced tactics — a mate in one or two, a hanging piece, a fork — because those are exactly what a shallow search with a capture extension finds well.
It is much weaker at quiet positions, where the right move is right for reasons that only show up ten moves later. If the evaluation is near zero and no captures are available, treat the suggestion as one reasonable option rather than the answer.
And it cannot tell you anything about your chess. Knowing the best move in a position you have already left is worth less than knowing which move you keep choosing across a hundred games and what it has cost you — which is what the report on your own history is for.
Frequently asked questions
What is a FEN string?
Forsyth–Edwards Notation: one line of text that describes a whole position — where the pieces are, whose turn it is, castling rights, en passant, and the move counters. Every chess site can export one, usually from a right-click on the board or a share menu.
Is this Stockfish?
No. This runs a negamax search with alpha-beta pruning and quiescence on the server, at a shallow depth. It finds sound moves and obvious tactics reliably, but it is not Stockfish strength and will not match a deep engine in quiet positions. The analysis board runs Stockfish in your browser if you want the stronger search.
How deep does it search?
Four plies, plus a quiescence extension that follows captures until the position is quiet. That is enough for forced tactics and mates in one or two, and not enough for long positional judgement.
Why is the evaluation different from Chess.com or Lichess?
Different engines at different depths disagree, particularly in closed positions. Treat the number as a rough reading. The move order matters more than the decimal.