Why free chess analysis is always capped at one game a day

Most free chess game review gives you one game per day. Chess.com works that way, and so does almost every smaller site offering the feature. I assumed for a long time that this was just a paywall placed where it hurts. It is partly that. But there is a real cost sitting behind the cap, and once I worked out what the cost was, I built my own analysis site differently. The cost of one game review Reviewing a 40 move game means evaluating about 80 positions. Give the engine two seconds on each one and you have spent close to three minutes of CPU. None of it is cacheable, because your game is not anyone else's game. Run that on your own hardware and you pay for every minute. A thousand people reviewing one game a day is roughly 50 CPU hours daily, for a feature you are giving away. The quota is not greed. It is the number that stops the free tier from eating the company. Which raises a more interesting question than "how do I price this". What happens if you delete the cost instead of rationing it? Move the engine to the client Stockfish compiles to WebAssembly. Put it in a Web Worker and the visitor's own processor spends those three minutes. Your server ships static files and never sees a chess position. The whole free tier problem disappears, because there is no per-user cost left to control. Nothing to meter, so nothing to cap. Getting started is unremarkable: const engine = new Worker ( " stockfish.js " ); engine . postMessage ( " uci " ); engine . postMessage ( " isready " ); After that you speak UCI over postMessage . Set a position, ask the engine to think, and read results off the message stream: engine . postMessage ( `position fen ${ fen } ` ); engine . postMessage ( `go depth 15 movetime 2000` ); That is the pitch. Now the parts nobody mentions. The protocol is strings, and it is asynchronous UCI was designed for a pipe between two processes. You get that pipe, faithfully, with all of its ergonomics intact. The engine answers with lines like this: info dept