Lumichess ("we", "us") is a chess analysis and training service available at lumichess.com and through our mobile apps. This policy explains what data we handle and why.
What we collect
Account information. If you create an account, we store your email address, display name, and sign-in identifiers from the provider you choose (Google, Apple, or Lichess). Authentication and our database are operated on Supabase.
Chess platform usernames. If you connect or enter a Chess.com or Lichess username, we fetch publicly available games and statistics for that username from the platform's public API to generate your reports, insights, and training content.
Your training data. Puzzle results, ratings, training progress, and saved reports are stored against your account so your progress persists across devices.
Usage analytics. We use Google Analytics and Vercel Analytics to understand how the site is used (pages visited, approximate location, device type), plus our own basic event tracking. This data is aggregated and not used to identify you personally.
What stays in your browser
Chess engine analysis (Stockfish) runs locally in your browser or app — your moves are not sent to our servers for evaluation. Game caches, puzzle databases, and preferences are stored locally using your browser's storage.
Advertising
Where ads are shown, they are served by Google AdSense, which may use cookies or device identifiers to show relevant ads. You can learn more in Google's advertising policies.
What we don't do
We don't sell your personal data. We don't send you marketing email without consent. We don't collect more than the service needs to work.
Third-party services
We rely on: Supabase (authentication and database), Vercel (hosting and analytics), Google Analytics (usage analytics), Google AdSense (advertising, where shown), and the public APIs of Chess.com and Lichess (game data). Playing live games connects you to Lichess under Lichess's own terms and privacy policy.
Data retention and deletion
Your account data is kept while your account is active. To delete your account and associated data, contact us at lumichessofficial@gmail.com and we will remove it.
Children
Lumichess is a general-audience chess service and is not directed at children under 13. We do not knowingly collect personal information from children under 13.
Changes
If this policy changes, we will update this page and the date above.
Contact
Questions about this policy: lumichessofficial@gmail.com