Chess Board Editor & FEN Builder

Set up any chess position by placing, moving and removing pieces, then get its FEN, a board diagram and a legality, check and mate check.

Need the FEN of a puzzle from a book, or want to set up an endgame to analyse? This editor builds any position from short text commands — place, move or remove pieces, starting from an empty board, the normal starting position or a FEN you paste — and returns the FEN together with a board diagram. It performs basic checks: one king each, no pawns on the back ranks, no side left in check out of turn, and whether the side to move is mated or stalemated.

How to use this tool

Choose where to start: empty board, starting position or a FEN you paste.
Type edits: Qd4 places a White queen, qd4 a Black one, e2e4 moves a piece and xd4 empties a square.
Set the side to move, castling rights and an en passant square if there is one.
Copy the FEN into your chess app or engine, and check the status line for problems.

Formula

FEN = ranks 8→1 / side to move / castling / en passant / halfmove clock / move number

Each rank lists pieces from the a-file to the h-file: uppercase is White, lowercase is Black (K king, Q queen, R rook, B bishop, N knight, P pawn), and a digit counts empty squares. "-" means no castling rights or no en passant square.

Example

Start from the standard position and enter f2f3 e7e5 g2g4 d8h4, White to move, halfmove clock 1, move 3. The editor returns rnb1kbnr/pppp1ppp/8/4p3/6Pq/5P2/PPPPP2P/RNBQKBNR w KQkq - 1 3, reports White is checkmated and 0 legal moves — the Fool's Mate.

Frequently asked questions

Why does the editor say my position is not legal?

Most often a king is missing, a pawn stands on the first or last rank, or the side that is not to move is in check. Engines and many chess sites refuse such FENs, so fix the listed problem first.

Does moving a piece here follow the rules?

No — e2e4 simply moves whatever is on e2, which is what you want when setting up a position. Use a notation converter if you need moves checked for legality.

When should I enter an en passant square?

Only right after a pawn has advanced two squares: give the square it skipped, such as e3 after e2–e4. The editor checks the double-moved pawn and skipped square; an adjacent capturing pawn is not required by FEN.

How are castling rights decided?

By default a side may castle on a wing when its king and that rook stand on their original squares. If they have moved earlier in the game, choose "No castling" or keep the rights from the FEN you loaded.

Sources

Last updated: 2026-10-30