ChessyAI Chess Coach appSet up any position or paste a game and Stockfish 18 analyzes it right in your browser, with an eval bar and the engine's best lines. Free, no account, nothing to install.
What this analysis board does
This is a free chess analysis board with the Stockfish 18 engine built in. Stockfish is one of the strongest chess engines in the world, and here it runs entirely in your own browser. Your positions are not sent to a server to be analyzed, there is no account to make, and the engine keeps working even on a slow connection once the page has loaded. How fast it goes depends on your device: a recent laptop reaches a useful depth in a few seconds, and a phone takes a little longer.
How to use it
Analyze a position
Make moves on the board by dragging or tapping the pieces. The engine starts thinking straight away and updates as it searches deeper. You can step back and forward through the moves you have played and try other ideas from any point.
Set up any position with the board editor
Open the board editor to place pieces exactly where you want them. This is useful for a position from an over-the-board game, a puzzle from a book or a diagram someone sent you. Set whose turn it is and the castling rights, then go back to analysis. You can also paste a FEN, the one-line text format that describes a chess position, to load it instantly.
Load a whole game from a PGN
Paste a PGN, the standard text format for a chess game, and the board loads every move. Both Chess.com and Lichess let you copy or download the PGN of any game. Then step through it and see what the engine thinks of each move. If you would rather have the whole game graded for you, with accuracy and move labels, use the free game review instead.
Share a position
The current position is stored as a FEN in the page URL. Copy the link and anyone who opens it sees the same position on the same board. That makes it easy to ask a friend or a coach, "what should I have played here?"
Reading the engine output
The eval bar
The bar beside the board shows who is better and by how much. The number is measured in pawns, from White's point of view:
| Evaluation | What it roughly means |
|---|---|
| 0.0 to ±0.5 | About equal |
| ±0.5 to ±1.5 | One side is somewhat better |
| ±1.5 to ±3 | One side is clearly better, often about a piece's worth of advantage in practice |
| Beyond ±3 | Usually winning with good play |
| M3, −M5 and so on | A forced checkmate in that many moves (negative means Black mates) |
A positive number favors White and a negative one favors Black. These ranges are a rough guide, not a rule. A +2 position can still be hard to win for a human, and a "0.0" can hide a lot of danger for the side that has to find only moves.
Best lines (MultiPV)
Below the board the engine shows its top few candidate lines, each with its own evaluation. This is called MultiPV. It's more useful than a single best move, because you can see whether the top move is far ahead of the rest or whether three moves are all about equal. If several lines score within a few tenths of a pawn, any of them is fine, and you should pick the one you understand.
Depth
Depth is how many moves ahead the engine has searched. Higher depth means a more reliable evaluation. In quiet positions the top move can change between depths as the engine searches further, so don't treat a small difference as meaningful.
How to use an engine to actually improve
An engine tells you what is best. It doesn't tell you why, and it can't learn for you. Some habits that make engine analysis worth the time:
- Guess first, then check. Before you turn the engine on, decide what you would play and why. Then compare. The gap between your guess and the engine's answer is what you're there to learn.
- Look for the turning point. In most lost games there is one or two moves where the eval swings hard. Spend your time there, not on move 4.
- Ask what the engine's move does. Play the best line forward a few moves until the point becomes clear: a piece wins, a threat appears, a pawn falls.
- Don't chase tiny differences. A move that loses 0.2 pawns is not a mistake worth studying. A move that loses 2 pawns is.
Our guide on how to analyze your chess games covers a full review routine, and how to review games without an engine explains why your own first look matters so much. For what accuracy scores mean once a whole game is graded, see what accuracy means in chess.
Other free tools
If you want to see patterns across many games instead of one position, run the chess weakness report. To check whether your rating is about where it should be on another site, use the rating converter. And if you want a laugh, try Roast My Chess. The full list of tools and guides is in the guides section.
Chessy — AI Chess Coach app goes a step beyond the board: it analyzes every game you play, turns your own mistakes into puzzles and has a coach that can explain the engine's moves in plain words.