Analyze any chess position or game: set up pieces by hand, paste a FEN or a full PGN, and step through the moves while an engine shows the evaluation bar and the best continuations.
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White to move
Set up a position: pick a piece, then tap squares (tap again to remove).
No moves yet. Make a move on the board or load a PGN.
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How to use the Chess Analysis Board
Load a game or position. Paste a PGN and press Load PGN, paste a FEN and press Load FEN, or press Set up position to place pieces by hand.
Step through the moves with the arrow buttons, by clicking a move in the list, or with the ← and → keys.
Read the evaluation. The bar and the score show who is better (positive = White); each line lists the engine's suggested continuation.
Try your own ideas by moving pieces on the board; the analysis updates instantly. Click an engine line to play its first move.
Save your work with Copy FEN, Copy PGN or Download PGN.
Reading the evaluation
Score
Meaning
Typical situation
0.00 to ±0.30
Equal
Balanced openings, symmetrical positions
±0.30 to ±0.90
Slight edge
Better development, a small structural plus
±0.90 to ±2.00
Clear advantage
An extra pawn, a strong attack
beyond ±2.00
Winning advantage
An extra minor piece or a decisive attack
#N / #-N
Forced mate
White (#N) or Black (#-N) mates in N moves with best play
Positive numbers favour White and negative numbers favour Black. One pawn is roughly 1.00; engines also count king safety, piece activity and pawn structure, so a material count and the score do not always match.
Tips for analyzing your games
Find the turning point: step through the game and watch for big jumps in the evaluation bar. A swing of more than a pawn usually marks a mistake.
Compare your move with the engine's: go back one move, look at the top lines and ask why the engine prefers them.
Try the alternative: play the engine's suggestion on the board and follow the line a few moves to see the idea.
Use several lines: with 2 or 3 lines you can see whether the best move is the only good move or one of many.
Let it think: early depths can change their mind. Wait until the depth number stops climbing in critical positions.
Frequently asked questions
Which engine analyzes the positions?
By default the board loads Stockfish 10, a free open-source chess engine, compiled to WebAssembly (or asm.js on older browsers) and running in a background thread on your device. If it cannot load, for example offline or on a blocked network, a built-in JavaScript engine with alpha-beta search takes over automatically. It is weaker but still finds tactics.
How do I read the evaluation score?
Scores are in pawns from White's point of view: +1.00 means White is about a pawn better, -2.50 means Black is two and a half pawns better, and 0.00 is equal. #3 means White can force mate in 3 moves and #-2 means Black can force mate in 2. The bar fills with white as White's advantage grows.
What does depth mean?
Depth is how many half-moves (plies) the engine searches ahead in its main line. Higher depth gives more reliable evaluations but takes longer. Depth 16 to 20 is a good balance in a browser; the built-in engine searches for about six seconds instead.
What PGN features are supported?
Standard tag pairs (including SetUp and FEN for games that start from a custom position), move numbers, comments in braces or after semicolons, numeric annotation glyphs such as $1, annotation symbols like ! and ?, and the result. Side variations in parentheses are skipped and only the main line is loaded.
What is FEN?
Forsyth–Edwards Notation describes a single position in one line: the pieces rank by rank from the 8th rank, the side to move, castling rights, the en passant square, the halfmove clock for the 50-move rule and the move number. The starting position is rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1.
Why is my position rejected in the editor?
A legal position needs exactly one king per side, no pawns on the first or last rank, and the side that is not to move must not be in check. Castling rights are kept only when the king and rook are on their original squares.
Are my games uploaded anywhere?
No. Parsing, the board and the engines all run in your browser. The only network request is downloading the Stockfish program file from a public CDN; your positions and games never leave your device.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.