Privacy
What this app knows about you
Short version: there is no server, no account, no analytics and no cookies of ours. Everything the app remembers lives in your own browser. A few things do leave it, and they are listed here exactly.
Stored in your browser only
The app uses your browser's local storage, which nothing but this site can read. It holds: your preferences (theme, board, pieces, sounds, time control, puzzle filters); the chess.com username you last typed; cached game analyses so a reviewed game reopens instantly; your puzzle record, rating and a local pool of puzzles already fetched; your Train records; an in-progress Play game so you can resume it; cached lessons; and, if you added one, your OpenRouter API key. None of this is sent to us; there is no us to send it to.
What leaves your browser, and to whom
chess.com: the username you type is sent to chess.com's public API to fetch that account's public games and statistics, the daily puzzle, and the public leaderboards. Nothing else is sent. chess.com's own privacy policy governs what it logs.
Lichess: requests for rated puzzles and Learn examples. They carry no personal data; like any web request they include your IP address.
OpenRouter: only if you add an API key in Settings. The app then sends your key and the text of each request to OpenRouter, which forwards it to the model you chose. Those requests contain chess positions, moves and engine evaluations. When the coach reviews a game, the prompt also includes the two player usernames and ratings from that game, and the result. Play and Learn prompts contain no usernames. OpenRouter's and the model provider's policies govern their logging. Remove the key in Settings and these requests stop.
Netlify: hosts the site and, like any host, keeps standard server logs (IP address, browser, pages requested). Netlify also inserts a small script of its own into pages. Netlify's privacy policy governs this.
Stockfish runs entirely inside your browser. No position is sent anywhere to be analysed.
What we do not do
No analytics or tracking of ours. No advertising. No cookies set by the app. No account, so nothing to breach. No selling or sharing of anything, because we hold nothing.
Removing everything
Clearing this site's data in your browser removes all of it. So does this button, which deletes every item the app has stored, including a saved API key.
Questions
Reach the author on GitHub or X. Last updated 17 September 2026.