Chess FEN Viewer & Editor
View any chess FEN as a board, edit the position square by square, and validate all six fields.
- Side to move
- White to move
- Castling
- White: kingside, queenside · Black: kingside, queenside
- En passant target
- None
- Halfmove clock
- 0
- Fullmove number
- 1
- Pieces on board
- 32
- White material
- 39
- Black material
- 39
- Balance
- Even
Everything runs in your browser — the FEN you paste is never uploaded, logged or stored.
How it works
A FEN (Forsyth–Edwards Notation) string records a complete chess position in six
space-separated fields: piece placement from rank 8 down to rank 1, the side to move
(w or b), castling rights (KQkq), the en passant target
square, the halfmove clock used for the fifty-move rule, and the fullmove number. Paste a FEN
and the board redraws instantly; every field is checked, so a rank that does not add up to
eight squares or a stray character is reported straight away.
It is also an editor. Pick a piece from the palette and click (or tab to and press Enter on) any square to place it, choose “Empty” to clear a square, and adjust the side to move, castling rights, en passant square and move counters — the FEN box rewrites itself as you go. Material is scored with the classic values pawn 1, knight 3, bishop 3, rook 5, queen 9 (kings are not counted), so the starting position reads 39 for each side. Legality warnings — missing or duplicate kings, pawns on the back rank, an en passant square on the wrong rank, castling rights with no rook to match — appear below the board without blocking your edits, because puzzle and study positions are often deliberately odd.
Frequently asked questions
What is a FEN string in chess?
FEN (Forsyth–Edwards Notation) records a whole position in six space-separated fields: piece placement from rank 8 down to rank 1, the side to move (w or b), castling rights (KQkq), the en passant target square, the halfmove clock for the fifty-move rule, and the fullmove number. The starting position is rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1.
Why does my FEN show an error?
Every field is checked as you type. The usual causes are a rank that does not add up to eight squares, a letter outside KQRBNPkqrbnp, a side-to-move field that is not w or b, or an en passant square on a rank other than 3 or 6. The message names the exact rank or field so you can fix it in one edit.
Can I edit the position and get a new FEN?
Yes. Choose a piece from the palette and click any square to place it, or choose Empty to clear one, and adjust the side to move, castling rights, en passant square and move counters — the FEN box rewrites itself instantly and you can copy or download the result.