Fen Viewer

The tool accepts a FEN string and outputs a visual 2D chessboard along with a parsed state that captures piece placement, side to move, castling rights, and en passant status. It is designed for players, coaches, analysts, and educators who need quick position verification without specialized software. Conceptually, the system tokenizes the FEN, validates syntax, maps each character to a board square, and establishes a coordinate-based representation that can be rendered or consumed by AI agents for further processing. Unique value lies in its immediate, machine-friendly outputs, robust error diagnostics, and no-dependency setup. Core features include a standards-compliant parser, square-based board construction, active color and rights extraction, and optional export of the board as SVG or FEN. Use cases cover puzzle verification, game commentary preparation, teaching demonstrations, and rapid position sharing across teams. The tool is beneficial for both beginners and advanced players seeking reliable, portable position visualization. Advanced users can leverage the machine-readable state for automated analysis pipelines. Exports to SVG enable reproducible visuals for reports; parsing results can feed external evaluators or chess engines. The approach prioritizes correctness, performance, and clear error messages to accelerate learning and collaboration.