Privacy policy

What we collect

• Chess games you ask us to analyze. When you enter a username, we fetch the public games for that account from chess.com or lichess and store the games and our analysis of them so we never have to analyze the same game twice. These are already public on those platforms.
• Account details, if you sign up. Your email and a securely hashed password (or your Google profile if you use Google sign-in), your linked chess username, your Pro status, and - if you choose to sync - your practice games and drill progress.
• Basic usage analytics (Google Analytics and/or PostHog Cloud EU), if enabled, to see which features people use. Standard server logs and error records for keeping the site up.

What we send to third parties

• Anthropic (Claude): chess positions and moves from analyzed games, to generate the plain-English explanations. No personal details beyond what is in a public game record.
• Stripe: handles payments. We never see or store your card number.
• UseSend: sends password-reset and (opt-in) weekly digest emails.

Error monitoring

We use self-hosted error monitoring (Sentry) that runs on our own servers, not a third-party service. When something goes wrong, technical diagnostic data (the error message, a stack trace, your browser and device type, the page URL, and a timestamp) is sent to our own servers so we can track down and fix the bug. We do not attach personal identifying information by default, and this data is not shared with third parties.

What we don't do

• No selling or sharing of your data with advertisers. Ever.
• No tracking across other websites.
• No emails unless you asked for them (reset links, or a digest you opted into).

Cookies

One session cookie keeps you signed in. Preferences (like the jargon dial) live in your browser's local storage, not on our servers, unless you sign in and sync.

Deleting your data

Email [email protected] (or use our contact form) from your account email and we'll delete your account and synced data. Analysis of public games may be retained since it contains nothing personal.