SAN (Standard Algebraic Notation)

SAN is how chess moves are written. Each move is one short string:

• Pawns: just the square, e.g. e4, exd5 (e-file pawn captures on d5)
• Pieces: letter then square. K=king, Q=queen, R=rook, B=bishop, N=knight. Examples: Nf3, Bb5, Ke1
• Capture: x between piece (or file for pawns) and square: Nxe5, exd5
• Castling: O-O (kingside), O-O-O (queenside)
• Promotion: add = and the new piece, e.g. e8=Q
• Check: + at the end (optional). Checkmate: # at the end (optional).

Files are a–h (left to right for White). Ranks are 1–8 (White's back rank is 1). So e4 is the pawn to the e4 square.