Mathalon for schools

What this is

Mathalon is a free competitive mental-math site — timed problems, ratings and leaderboards, in the spirit of what Lichess is for chess. It is built and run by a 15-year-old and his father in Sweden. There are no ads and nothing is sold, including data.

Personal data

Without an account (guest mode): no account, no name, no email — nothing a student enters identifies them. Like every website, the server sees IP addresses for security and rate limiting; they are not used for anything else.

With an account: an email address, a chosen username and a birth year. That is the whole list. Registration under 13 is blocked (the GDPR Article 8 age of digital consent as set by Sweden), and new accounts must verify their email address before signing in. Users can delete their own account themselves, from settings — no email to us required.

The data controller is named, with contact details, in the privacy policy.

Where the data lives

The application and its PostgreSQL database are hosted on Railway in the Netherlands (region europe-west4), inside the EU. The one processor outside the EU is listed in the next-but-one section.

Communication between students

There is no chat. Not in matches, not in rooms, not anywhere on the site. Nothing a student types is ever shown to another user — answers go to the grader, not to people.

What one user can see of another: the username, rating and leaderboard position. In a live match an opponent sees your username and score, nothing else. Friend requests exist, but accepting one only adds the person to a private leaderboard and lets them challenge you to a match — it opens no channel to write to you.

Mathalon has a community Discord server. It is a separate, voluntary platform under Discord’s own terms and age rules — it is not part of the site, is not linked from the game, and no student needs it to use anything on mathalon.app.

Ads and tracking

No ads, no data sales, no advertising or analytics cookies, and no third-party analytics of any kind — no Google Analytics, no tracking pixels, no fingerprinting. The site records gameplay events (problem started, answer submitted) in its own database to make ratings work; that data never leaves the service.

The complete list of third parties that process any user data:

• Railway — hosts the servers and database (EU, see above).
• Resend — delivers transactional email only: verification and password-reset messages. A US provider; the transfer is covered by Standard Contractual Clauses. Resend sees the email address and the message it delivers, nothing else.

That is the entire list. If it ever grows, this page changes first.

Cost

Mathalon is free, and will remain free at least until the site is many times its current size. There is no paid tier, no locked content and no plan to paywall anything a class starts depending on mid-term.

Contact

Questions from schools are answered by Peter Christer Andreas Nödtveidt, the responsible adult behind the site: [email protected]. Plain questions get plain answers — including “no” when the honest answer is no.