ChessMIKU Privacy Policy

Effective 26 September 2026

ChessMIKU is a free browser extension that reviews your finished games from chess.com: the Stockfish engine evaluates the game in your browser, and our server turns the evaluations into plain-language explanations of the worst moves. This page says what data that takes, where it goes and how long it stays.

ChessMIKU is an independent project and is not affiliated with Chess.com.

What is sent to the ChessMIKU server

Only finished games, and only when you press Review game. Nothing is sent while a game is in progress, and ChessMIKU never gives hints during a game. For the game you chose to review, the extension sends:

• the game's PGN, which contains both players' chess.com usernames and the date of the game;
• the game's chess.com number;
• the engine evaluation of every move, computed in your browser;
• the language you want the explanations in;
• an anonymous installation ID, which our server issues when the extension first contacts it. It is a random number and is not linked to your name, email or chess.com account.

What we do not collect

No accounts, passwords or email addresses, no browsing history and nothing from other websites. On chess.com game pages the extension looks only at the page address, its title and whether the game has ended, to decide when to show the Review game button.

What stays in your browser

The extension keeps the installation ID, a cache of engine evaluations, your chosen language and the review panel's settings in your browser's extension storage. None of it leaves your device, except the installation ID and the language, which travel with a review request as described above.

Other services involved

• Chess.com. The extension reads the game, player avatars and titles from chess.com's public API, directly from your browser. Chess.com's own privacy policy applies to those requests.
• Cloudflare. Our server is reached through Cloudflare Tunnel, so requests to it pass through Cloudflare's network.
• Google Gemini. To write the explanations, the server sends the game's moves and their evaluations to the Google Gemini API. We use Gemini's free tier, and Google may use data sent to it to improve its products and models, under Google's terms for the Gemini API.

IP addresses

The server uses your IP address only in memory, for rate limiting: to limit how many installation IDs one address can request, and how often a request without an installation ID can be made. It is never written to the database.

How long data is kept

Reviewed games, their evaluations and explanations, installation IDs and daily review counts are kept in our database for as long as the service runs. Reviews are a shared cache: when the same game is reviewed again, for example by your opponent, the saved explanations are reused instead of asking Gemini again. To have a game deleted, email us a link to it.

How data is used

Only to review games and to enforce the daily review limit. We do not sell data, do not share it for advertising, and do not use it to determine creditworthiness or for any purpose unrelated to reviewing games.

Changes and contact

If this policy changes, the date at the top of this page changes with it. Questions and deletion requests: support@softgene.dev.