Not every position comes with a picture. You remember the moment your club game went wrong, a friend describes an endgame, or a forum post gives a FEN string. ChessWOW's board editor lets you place the pieces yourself, checks that the position is legal, and hands it to Stockfish 19 or to you and an opponent to play on.
When the editor is the right tool
- Over-the-board games. After a tournament or club game, set up the position where you were unsure and see what the engine says.
- Endgames and studies. Set up a textbook endgame, such as king and pawn against king, and practise it against Stockfish until the technique is automatic.
- Positions shared as text. Paste a FEN or a PGN from a website, an email or another chess program.
- Fixing a scan. If a scanned diagram needs many corrections, it is often quicker to build the position directly.
How to set up a position in four steps
- Step 1
Open the editor. Tap "Set up position". On a Mac the shortcut is ⌘B.
- Step 2
Place the pieces. Pick a piece from the tray and tap the squares where it belongs. Tap a square again to change or clear it. You can start from an empty board or from the starting position.
- Step 3
Set the details. Choose whose move it is. Enable castling rights only for a king and rook that have not moved yet, and en passant only if the last move was a pawn advancing two squares.
- Step 4
Analyze or play. Start the analysis to see the evaluation, the best move and up to three lines, or play the position against Stockfish or with a second player on the same device.
Legal positions only
An engine needs a position that could occur in a real game. ChessWOW checks this before it starts and tells you what is wrong: each side needs exactly one king, pawns cannot stand on the first or last rank, a side cannot have more than eight pawns, and it cannot have more pieces than promotions allow. The side not to move must not be in check. These checks catch most typos in hand-built positions.
- One king per side
- No pawns on rank 1 or 8
- At most eight pawns per side
- Side not to move is not in check
FEN in two minutes
FEN (Forsyth-Edwards Notation) describes a position in one line of text. The starting position looks like this:
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1- Piece placement. Ranks from 8 down to 1, separated by slashes. Capital letters are White (K king, Q queen, R rook, B bishop, N knight, P pawn), small letters are Black, digits count empty squares.
- Side to move.
worb. - Castling rights.
KandQfor White's kingside and queenside,kandqfor Black,-if none. - En passant square. The square a pawn skipped over on the last move, or
-. - Halfmove clock. Moves since the last capture or pawn move, used for the fifty-move rule.
- Move number. Starts at 1 and increases after Black's move.
In ChessWOW you can paste a FEN to load a position and copy the current position as FEN to share it. A full game in PGN works the same way: paste it, and the moves load onto the board.
From the editor to practice
A position you set up is saved like any other game. You can return to it, play it again at a different level, or compare your moves with the engine afterwards. For endgames with few pieces, the optional endgame tablebase makes Stockfish's verdict exact.
Questions and answers
Can I paste a FEN?
Yes. Paste a FEN or a whole PGN game and the position loads onto the board. You can also copy the current position as FEN.
Why does ChessWOW say my position is invalid?
Usually the wrong side is set to move, or a king is missing. Each side needs one king, pawns cannot stand on the first or last rank, and the side not to move must not be in check.
When should I enable castling rights?
Only if the king and that rook have not moved in the game. A picture or a hand-built position alone cannot prove it.
Can I play the position against someone?
Yes. Play it against Stockfish at one of five levels, or with a second player on the same device.
Is there a keyboard shortcut on the Mac?
Yes, ⌘B opens the editor.
Continue with
Try it on your next position.
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