On the analysis board you replay a game and have every position evaluated by a chess engine. This shows you where a game turned, which move the engine would have preferred and how your own ideas work out.
Loading a game
Paste a game as PGN into the field below the board. The analysis starts by itself as soon as the text is there.
For finished games it is quicker. Correspondence games, live games and games against the chess computer have a link to the analysis board, the PGN is then already in the field.
The analysis board remembers the last game and the evaluations it has already calculated in your browser. Next time you continue where you left off. If you clear the field, the stored game is gone as well.
Moving through the game
Above the notation you find the buttons for the first move, one move back, one move forward, the end of the line, deleting a move and turning the board. You can also click any move in the notation directly.
With the keyboard it is faster.
- Arrow left and arrow right, one move back and one move forward. The keys j and k do the same
- Arrow up, to the starting position
- Arrow down, to the last move of the line
- Delete or backspace, delete the displayed move and everything after it
The numbers in the notation
Next to every move you see the evaluation of the position that is on the board after that move. One row of the notation consists of five fields.
| Field | Meaning |
|---|---|
| 12. | move number |
| Nxe5 | White's move |
| +0.3 | evaluation after White's move |
| Qh4 | Black's move |
| -1.4 | evaluation after Black's move |
The evaluation is always from White's point of view and is counted in pawns.
- +1.0 means White stands as well as if he had one pawn more.
- -1.0 means the same for Black.
- 0.0 is a balanced position. Everything between about -0.5 and +0.5 counts as equal.
- #3 means there is a forced mate in three moves.
The bar next to the board shows the same evaluation graphically, White from the bottom, Black from the top.
The colors of the numbers
The color compares the evaluation with the evaluation before the move and therefore tells you what the move changed.
- Red and bold, the move worsened your own position by at least one pawn, a blunder.
- Yellow, an inaccuracy, the loss is between half a pawn and a full pawn.
- Green and bold, your own position improved by at least one pawn.
- Grey, the move changed little about the evaluation.
The numbers that stand out are the interesting ones. Wherever the evaluation jumps by a pawn or more, a closer look pays off.
The arrows on the board
For every displayed move the board shows up to two arrows.
- The green arrow is the move the engine would have played in this position.
- The second arrow is the move that was actually played. It only appears when it differs from the suggestion and is red for a blunder, yellow for an inaccuracy and grey otherwise.
Above the notation there is a short sentence about it, either "The computer would have made this move too" or a suggestion like "The computer suggests e2-e4".
Your own moves and variations
You can move on the board at any time, for both colors. If the displayed move is the last one of the game, the line simply continues. In the middle of a game the analysis board creates a variation, which is shown below the move and evaluated as well.
The PGN field is kept up to date while you do this, so you can copy the game including your variations from there at any time. The delete button, and the delete key, take back the displayed move and everything after it.
The link "Free board" below the board opens a layer where you can move, add and remove pieces freely, without regard for the rules. It is meant for showing and trying out ideas and does not change the analysis.
Analysis depth
Below the notation you set how many half moves the engine calculates ahead. A greater depth is more precise and takes longer. After a change the game is calculated again, the setting is kept for your next visit.
The engine runs in the browser, on your own device. How long an analysis takes therefore depends on the depth and on the device. Above the notation you can watch the progress. Positions that have been calculated once are remembered, which makes a second run fast.
What the evaluation is not
The number is the assessment of an engine at the configured depth, not a final verdict about the game. Changes of one or two tenths mean nothing. An engine also evaluates a position, not the plan behind it. The best move in the eyes of the engine is not always the move a human can find at the board.