Terms of Service

Last updated: June 2026

1. Acceptance of Terms

By accessing or using ChessMeris ("the Service"), you agree to be bound by these Terms of Service. If you do not agree, please do not use the Service.

2. Description of Service

ChessMeris is a free online platform for chess puzzle training. It offers puzzle modes, ELO tracking, streaks, achievements, and social features. All features are currently free of charge during the launch period.

3. User Accounts

You may use the Service as a guest (limited access) or by creating an account with a valid email address. You are responsible for maintaining the confidentiality of your account credentials and for all activities that occur under your account.

You must not create accounts for other people without their permission, use the Service for any unlawful purpose, or attempt to disrupt the Service.

4. User Content

You may provide a display name, country, and avatar as part of your profile. You agree not to use offensive, impersonating, or misleading display names. We reserve the right to remove any content that violates these terms.

5. Intellectual Property

The puzzle database used by ChessMeris is sourced from Lichess.org under the Creative Commons CC0 license. The ChessMeris platform, design, and code are the property of the Service operator. You may not copy, modify, or redistribute them without permission.

6. Disclaimer of Warranties

The Service is provided "as is" without warranties of any kind. We do not guarantee uninterrupted access, error-free operation, or permanent data retention. We reserve the right to modify or discontinue the Service at any time.

7. Limitation of Liability

To the fullest extent permitted by law, ChessMeris and its operator shall not be liable for any indirect, incidental, or consequential damages arising from your use of the Service.

8. Changes to Terms

We may update these Terms at any time. Continued use of the Service after changes constitutes acceptance of the new Terms. We will notify users of significant changes via email when possible.

9. Contact

For any questions regarding these Terms, please contact us at contact@chessmeris.com.

Privacy Policy

Last updated: September 2026

1. Data Controller

The data controller responsible for your personal data is:

John D.
Operating as ChessMeris
Email: contact@chessmeris.com

2. Data We Collect

When you create an account and use ChessMeris, we collect the following data:

  • Account data: email address, hashed password
  • Profile data: display name, country, avatar selection
  • Game data: ELO ratings, puzzles solved, streaks, achievements, theme statistics, sprint and survival scores, the puzzles you missed (Review mode), your Daily puzzle results (your display name, country and result appear on the public leaderboard of the day). The global leaderboards (Puzzle, Sprint, Survival) are public too: if you rank in them, anyone can see your display name, country and score there (ELO and puzzles solved, or best Sprint / Survival score). The rest of your profile stays visible only to you and your accepted friends.
  • Social data: friend relationships and requests, challenges between friends (the puzzle and both results, visible to the two players)
  • Lichess data (only if you connect Lichess): your Lichess username and puzzle rating, and the list of puzzles you missed there. You sign in on lichess.org: we never see your Lichess password, the access Lichess gives us is limited to reading your puzzle activity and is revoked right after the import — unless you turn on the weekly sync: we then keep that read-only access, encrypted, to add the puzzles you miss on Lichess to Review once a week, until you turn the sync off or disconnect Lichess in Settings (the access is then deleted and revoked). You can disconnect Lichess at any time in Settings.
  • Your own games (only if you use “Your own mistakes” in Review): your public games on Lichess and/or Chess.com are downloaded by your browser and analysed on your device; we store only the puzzles found (position and moves, the game's link and date) and which games were analysed. The usernames you type are remembered in your browser only.
  • Premium subscription (only if you subscribe): your Stripe customer and subscription identifiers, your plan, its status and renewal date. Payment is made on Stripe's secure page: we never see or store your card number.
  • Technical data: IP address (via Supabase and Vercel infrastructure), browser type, device type (via Google Analytics, only if you accept cookies)

Guest users do not create an account and no personal data is stored beyond the current session — except, to apply the free guest limit (a few puzzles a day), a keyed fingerprint of your IP address and of a random id kept in your browser, with how many puzzles and runs they played today. Neither the address nor the id is stored in clear, and these counters are deleted after two days (legitimate interest: keeping the free offer fair).

3. How We Use Your Data

  • To provide and operate the Service (account management, game progress tracking)
  • To display your profile and statistics to friends you have accepted
  • To show the public leaderboards (global and Daily)
  • To send streak reminder emails when your active streak is about to break (at most one a day; turn them off in Settings or with the link in every email)
  • To send a weekly summary of your progress on Sunday, only in weeks you played (turn it off in Settings or with the link in every email)
  • If you turn on notifications on a device (Settings): to send the streak reminder there too. We store the address your browser's push service gives us for that device, nothing else; turn it off in Settings or in your browser at any time
  • To analyse usage and improve the Service via aggregated analytics

4. Legal Basis (GDPR)

  • Contract performance: processing necessary to provide the Service you signed up for
  • Legitimate interest: service security and improvement, including error monitoring (Sentry); streak reminder and weekly summary emails to account holders, which you can turn off at any time
  • Consent: analytics cookies (Google Analytics)

5. Data Retention

Your data is retained as long as your account is active. If you delete your account, all personal data is permanently deleted within 30 days. Anonymised aggregate statistics may be retained indefinitely.

6. Third-Party Services

We use the following third-party services that may process your data:

  • Supabase (supabase.com) — database and authentication. Data stored in EU region. Privacy policy
  • Vercel (vercel.com) — hosting and infrastructure. Privacy policy
  • Google Analytics (google.com) — usage analytics, loaded only if you accept cookies. Privacy policy
  • Sentry (sentry.io) — error monitoring: when the site crashes, a technical report (error message, page, browser and device type) is sent so we can fix it. No name, email, IP address or cookie is included, no session recording. Data stored in the EU (Frankfurt). Privacy policy
  • Lichess (lichess.org) — only if you choose to connect your Lichess account, to import your puzzle rating and history (once, or every week with the weekly sync) — and, if you use “Your own mistakes”, your browser downloads your public games from Lichess. Privacy policy
  • Chess.com (chess.com) — only if you use “Your own mistakes” with a Chess.com username: your browser downloads your public games from Chess.com's public API. Privacy policy
  • Stripe (stripe.com) — payment of the Premium subscription (card, invoices, cancellation), only if you subscribe. Stripe receives your email address and payment details directly. Privacy policy
  • Resend (resend.com) — email delivery (account emails, streak reminders, weekly summaries). Privacy policy

7. Your Rights (GDPR)

As a user based in the European Economic Area, you have the following rights:

  • Right of access: request a copy of your personal data
  • Right to rectification: correct inaccurate data via your profile settings
  • Right to erasure: delete your account and all associated data via Settings → Delete account
  • Right to data portability: request an export of your data
  • Right to object: opt out of analytics (via "Cookie settings" in the footer) or email communications

To exercise any of these rights, contact us at contact@chessmeris.com.

ChessMeris uses localStorage and sessionStorage to maintain your session and preferences, and to remember your cookie choice. These are strictly necessary and do not require consent.

Google Analytics cookies (_ga, _ga_*) are used to measure how the Service is used. They are only set if you click "Accept" on the cookie banner. If you decline, Google Analytics is not loaded at all. You can change your choice at any time via "Cookie settings" at the bottom of every page; withdrawing consent deletes these cookies.

Vercel Analytics and Speed Insights, used to measure site performance, and Sentry error monitoring do not use cookies. No advertising cookies are used.

9. Data Security

We implement industry-standard security measures including encrypted connections (HTTPS), hashed passwords, and row-level security on our database. However, no system is completely secure and we cannot guarantee absolute security.

10. Contact & Complaints

For any privacy-related questions or to exercise your rights, contact: contact@chessmeris.com

You also have the right to lodge a complaint with your national data protection authority (in France: CNIL).