Privacy Policy

Last updated: June 2026

1. Who We Are

CHESS.TRAIN is a personalized chess training platform. For questions about this policy, contact us at chess.train.app@gmail.com.

2. What Data We Collect

We collect only what is necessary to provide the service:

• Account data: username, hashed password (bcrypt), Chess.com username (optional)
• Training data: puzzle results, ELO rating, session history, streak information
• Activity logs: login timestamps, analysis events, session completions
• Server logs: IP addresses in standard web server access logs (retained max 30 days)

We do not collect: email addresses, real names, payment information, or device identifiers.

3. How We Use Your Data

• To provide personalized puzzle recommendations based on your game weaknesses
• To track your training progress and ELO rating
• To maintain login sessions (30-day session cookie)
• To generate AI coaching reports via the Anthropic Claude API (your Chess.com username and game data is sent to Anthropic for processing)

4. Third-Party Services

• Chess.com API: We fetch your public game history to analyze your play. Only publicly available data is accessed.
• Anthropic (Claude API): Your game analysis data is sent to Anthropic to generate coaching reports. Anthropic's Privacy Policy applies to this processing.
• Hetzner Cloud: Our servers are hosted in the EU (Nuremberg, Germany). Hetzner's Privacy Policy applies.
• Lichess: Puzzle data sourced from the Lichess open database. No personal data is shared with Lichess.

5. Cookies

We use a single session cookie strictly necessary for authentication. This cookie does not track you across sites, contains no personal data, and expires after 30 days of inactivity. No analytics, advertising, or third-party cookies are used.

6. Your Rights (GDPR)

If you are located in the European Union, you have the following rights:

• Right to access: Download all data we hold about you via Account Settings → "Download My Data"
• Right to deletion: Delete your account at any time via Account Settings → "Delete My Account"
• Right to portability: Your data export is provided in standard JSON format
• Right to rectification: Contact us to correct inaccurate data
• Right to complain: You may lodge a complaint with your national supervisory authority (Hungary: NAIH)

7. Data Retention

Your data is retained for as long as your account is active. When you delete your account, all profile data, puzzle results, and event logs are permanently deleted from our systems within 30 days.

8. Data Security

Passwords are hashed using bcrypt and never stored in plaintext. All connections use HTTPS. Access to the database is restricted to the application server.

9. Children

This service is not directed at children under 13. If you believe a child has registered, please contact us and we will delete the account.

10. Changes to This Policy

We may update this policy as the service evolves. Continued use after changes constitutes acceptance of the revised policy.

11. Contact

For any privacy-related requests or questions: chess.train.app@gmail.com