How to set up a position
- Start from the opening position or a clear board. Use Start position or Clear (which keeps nothing, not even the kings).
- Place the pieces. Pick a piece in the tray and tap the squares where it goes. Drag a piece to move it. Pick ✕ to remove pieces.
- Set the side to move and castling. Castling boxes only switch on when the king and that rook are still on their starting squares.
- Copy the FEN, or analyse. The FEN updates as you edit. The editor checks the position before you send it to the engine.
What a FEN is
FEN (Forsyth–Edwards Notation) describes a chess position in one line of text, so you can paste it into any chess program. The starting position is:
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
| Part | In the example | Meaning |
|---|---|---|
| Pieces | rnbqkbnr/…/RNBQKBNR | The 8 ranks from Black's side (rank 8) down to White's (rank 1). Capital letters are White, small letters Black: K king, Q queen, R rook, B bishop, N knight, P pawn. A digit counts empty squares. |
| Side to move | w | w for White, b for Black. |
| Castling | KQkq | Which castling moves are still allowed: K and Q for White's king side and queen side, k and q for Black. A dash means none. |
| En passant | - | The square a pawn can be captured on en passant, if the last move was a two-square pawn push. |
| Move counters | 0 1 | Half-moves since the last capture or pawn move (for the 50-move rule), then the move number. |
Setting up a chess board correctly
- Turn the board so each player has a light square in the right-hand corner.
- Put the rooks in the corners, then the knights, then the bishops.
- The queen goes on her own colour: the white queen on the light square d1, the black queen on the dark square d8. The kings go on the e-file next to them.
- Fill the second rank with pawns for White and the seventh rank for Black. White moves first.
What the editor checks
Before a position goes to the engine, the editor checks that each side has exactly one king, no pawn is on the first or last rank, no side has more than 8 pawns or 16 pieces, and the side that is not to move is not in check (that would mean the last move was illegal). If something is wrong it says what, in plain words.