The efficiency of wasm is really impressive. An optimised build of Stockfish with POPCNT evaluates positions at ~1500kn/s on a single core of machine. By contrast, the wasm build on https://lichess.org/analysis/r4rk1/p5b1/2p2n2/1p2p3/4P2q/P1N1B3/1PP1B1Q1/2KR3n_w#0 can compute ~42kn/s in the browser for the same position!