Privacy policy
This page explains what happens to your data on Sudoku Luna. The site is run from Switzerland and has visitors from the EU, so it follows both the Swiss Data Protection Act and the GDPR — where the two differ, the stricter rule applies.
Last updated: August 2026
Who is responsible
The operator named in the imprint is the controller for the processing described here. Write to the e-mail address given there for any question about your data, including access, correction and deletion.
The short version
You can play, print and learn without an account and without consenting to anything. Statistics and advertising only run if you allow them. Nothing on this site is sold to data brokers.
Data needed to run the site
A session cookie keeps you signed in. Your language, colour theme, settings and the puzzle you are currently solving are stored in your browser's local storage — they never reach our servers. This is what makes the site work at all, so it needs no consent, and it disappears when you clear your browser data.
If you create an account
We store your e-mail address, your display name and a hash of your password — never the password itself. Added to that are the things an account exists for: solved puzzles, times, streak, badges, learning progress, tournament entries and duels. You can delete your account by writing to us, and the data goes with it.
Server logs
Like every web server, ours records the requested address, time, browser type and IP address. These entries protect against attacks and let us find faults. They are deleted after 30 days at the latest and are not combined with anything else.
Statistics (only with consent)
If you allow it, we count which pages are visited using a self-hosted analytics service. It sets no advertising cookie, builds no profile across sites and does not pass data to third parties. We use it to see which pages help and which are ignored. Without your consent this script is not loaded at all.
Advertising (only with consent)
Advertising pays for hosting and development. With your consent, Google may set cookies to select and measure ads; that involves transferring data to Google and possibly to the United States. Without consent we show no personalised advertising and Google's advertising signals stay switched off. The game works fully either way.
Your consent, and how to take it back
The banner asks separately for statistics and advertising, and refusing is exactly as easy as accepting. Your choice is stored locally in your browser, together with the date, and is not a cookie. You can change it at any time through the “Cookie settings” link in the footer — withdrawal takes effect immediately.
Contact form and e-mail
What you write in the contact form — name, e-mail address, subject, message — is sent to us by e-mail so we can answer. We keep such messages as long as the matter is open and delete them afterwards.
Reading a puzzle from a photo
The solver can read a printed puzzle from a photo. If you use it, your browser first shrinks the image and re-encodes it, which also removes the camera's metadata such as the location where the photo was taken. The reduced image is then sent to our server and passed to a recognition service to read the digits. We do not store the photo: it exists in memory for the moment of recognition and is gone afterwards, and only the 81 digits are returned to your browser. If you never use this button, no image leaves your device.
Your rights
You may ask what data we hold about you, have it corrected or deleted, restrict its processing, receive it in a portable form and object to processing. Consent, once given, can be withdrawn without giving reasons. A request costs nothing; write to the address in the imprint.
Complaints
If you believe we handle your data unlawfully, you may complain to the Swiss Federal Data Protection and Information Commissioner (FDPIC), or, if you live in the EU, to the supervisory authority of your country.
Changes to this policy
If the site starts processing data in a new way, this page changes with it and the date above is updated. If the change needs your consent, the banner asks again instead of assuming an answer you never gave.
Cookie settings
Decide for each purpose. You can change this at any time through the link in the footer.