Notes on chess engines
What we learned building a chess site — measured, not guessed
Chessy runs ten chess engines inside the browser and analyses your games with Stockfish. Building that turned up a lot of things we did not expect — about how engine strength limiting actually works, why brilliant moves are so hard to detect, and how a perfectly reasonable-looking rule can produce nonsense for months without anyone noticing. These are the write-ups. Everything in them was measured against real games rather than reasoned about, and where we got it wrong first, we have said so.
Your 400-rated chess bot is probably playing at 1320
Almost every chess bot on the internet runs on the same engine, and that engine has a strength floor it cannot go below. Ask for less and it does not refuse — it quietly ignores you.
ReadA brilliant sacrifice is invisible to the engine that proves it works
We spent weeks trying to make our analyser detect brilliant moves. It found nothing — not one famous sacrifice in chess history. The reason turned out to be the same reason the sacrifices are good.
ReadWe analysed 542 moves and the word “blunder” never appeared once
Including a move that walked into forced checkmate and threw away the equivalent of eighty-three pawns. Our analyser called it “good”.
ReadCheck any of it yourself
Every game referenced in these articles can be loaded into the analyser and stepped through move by move. The engines all run on your own machine, so there is nothing to install and nothing to take on trust. Open the analysis board or read our history of chess.