The FEN position analyzer evaluates a single chess position rather than a whole game. Paste a FEN string — the standard one-line text notation that describes piece placement, side to move, castling rights, and en passant square — and Stockfish returns an evaluation in centipawns along with its preferred continuations. The engine runs locally in your browser through WebAssembly, so the position never leaves your device.
FEN — Forsyth-Edwards Notation — encodes a complete chess position on a single line of text. It records where every piece stands, whose turn it is, which castling rights remain, whether an en passant capture is available, and the move counters. Because it is one line of plain text, a FEN is the standard way to move a position between chess programs, books, and puzzle collections.
Position analysis is the right tool when you already know which moment matters. Studying an endgame you keep drawing, checking whether a sacrifice you considered actually worked, or testing an idea from a book are all single-position questions. Analyzing the full game is better when you do not yet know where things went wrong.
Centipawns measure the engine's assessment of the position in hundredths of a pawn. An evaluation of +100 means White stands roughly one pawn better, and -250 means Black is about two and a half pawns ahead. A mate score is shown separately, since a forced mate is not measurable in pawns.
No. Stockfish is compiled to WebAssembly and runs inside your browser, so the evaluation happens on your own device. The position you paste is not transmitted for engine analysis.
Most chess sites and programs expose a FEN for the current position, usually near an export, share, or copy-position control. Puzzle collections and chess books also commonly print FEN strings alongside diagrams.
Use the game analysis tool for full games. This page is built for evaluating one position at a time, while the analysis tool takes a PGN and reviews every move in the game.