ChessImager - Using FEN position notation

Here are the basics. Lower-case letters indicate black pieces: p, r, n, b, q, and k are the pawn, rook, knight, bishop, queen, and king. Upper-case letters indicate white pieces: P, R, N, B, Q, and K. A digit indicates unoccupied squares. For example, the digit 3 indicates 3 successive unoccupied squares.

Starting with the 8th rank, you simply list the pieces and unoccupied squares in order, left-to-right. Ranks are separated by the forward slash. In my image example above, the FEN string started with r3k2r/p1pp1p2/. On the eighth rank, from left to right, there’s a black rook, 3 empty squares, a black king, 2 empty squares, and a black rook. Then on the seventh rank, there’s a black pawn, an empty square, two black pawns, an empty square, a black pawn, and two empty squares.

A complete FEN string also includes game information such as the move number, who’s on the move, castling privileges, etc. ChessImager, though, only uses the position information as described above.

Here’s the FEN string for the starting position:

rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR/

The position after 1.e4:

rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR

And after the response 1…c5:

rnbqkbnr/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/RNBQKBNR

rnbqkbnr/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/RNBQKBNR
After 1…c5