Perft tester

Counts the number of legal move sequences to a given depth from a FEN. Compares against reference values for the standard CPW positions and offers a per-root-move divide breakdown — the canonical way to localise a move-generation bug.

Runs in your browser using a small vanilla-JS move generator built from the project's move-generation series.

FEN

Preset positions

Depth

Show divide

Use .NET WASM engine when available

Engine: pure-JS (WASM not loaded yet)

Result

—

Divide

Per-root-move counts at depth − 1, sorted alphabetically. Compare against your engine's go perft output to find the misbehaving root.

Move	Nodes

Total —

Reference perft values

Position	1	2	3	4	5	6

From chessprogramming.org/Perft_Results.