Privacy policy

1. Data controller

The data controller is the publisher of Blunderland, identified in the footer. For any question about your data, use the contact address shown at the bottom of the page.

2. Local first

By default, your data (saved usernames, generated puzzles, review progress, language preference) stays in your browser's local storage. It is neither sent to a server nor accessible to the publisher. Clearing your browser data deletes it permanently.

3. Data processed and purposes

Depending on how you use the app, the following data may be processed:

• Account: your email address, when you sign in with a one time code or via Google. Purpose: to authenticate you and save your progress. Legal basis: performance of the service you request.
• Synchronized progress: puzzles and review state, if you have an account. Purpose: to find your progress again on all your devices. Legal basis: performance of the service.
• Usage statistics (PostHog, Vercel Web Analytics): usage events, page views, technical information (browser and device type). Purpose: to understand usage and improve the app. Legal basis: legitimate interest, pseudonymized data.
• Error tracking (Sentry): technical reports in case of a bug. Purpose: to diagnose and fix problems. Legal basis: legitimate interest.

4. What we do not do

Blunderland does not sell your data, shows no advertising, does no advertising profiling, and does not share your data with third parties for commercial purposes. There is no paywall.

5. Data from chess platforms

To analyze a username, the app queries the public APIs of Chess.com and Lichess to fetch the public games associated with the username you enter. This data comes from public accounts and is processed in your browser to generate the puzzles. The Stockfish analysis runs entirely on the client side: positions are not sent to an analysis server.

6. Cookies and local storage

Blunderland uses the browser's local storage to run the app (these are not advertising trackers), a language preference cookie, and, if you sign in, authentication cookies. No third party advertising cookie is set.

7. Processors and hosting

To operate, the service relies on the following providers, acting as processors or suppliers:

• Vercel: website hosting.
• Supabase: database and authentication, only if you create an account.
• PostHog: audience measurement and usage statistics, hosted in the European Union.
• Sentry: technical error tracking.
• Google: sign in with a Google account, if you choose that option.

8. Transfers outside the European Union

Some providers (notably Vercel, Sentry and Google) may process data outside the European Union, in particular in the United States. These transfers are covered by appropriate safeguards, such as the European Commission's standard contractual clauses or the Data Privacy Framework. PostHog is hosted in the European Union.

9. Retention period

Local data: kept until you clear your browser. Account: kept as long as the account exists, then deleted on request. Usage statistics and error reports: kept for a limited period, in line with each provider's settings.

10. Your rights

Under the GDPR, you have a right of access, rectification, erasure, restriction, objection and portability over your data. You can exercise them via the contact address shown at the bottom of the page.

You also have the right to lodge a complaint with your data protection authority (in France, the CNIL, www.cnil.fr) if you believe your rights are not respected.

11. Minors

Blunderland is aimed at a broad audience. If you are under 15, ask a parent or guardian for consent before creating an account. The publisher does not knowingly collect data about children without such consent.

12. Changes

This policy may change. The last updated date appears at the top of the page; in case of a significant change, the information will be made visible in the app.