Privacy

What stays on your device

Play without signing in and nothing changes from how this site has always worked: progress, timers, and preferences are saved only in your own browser and never leave your device. Every puzzle, every hint and the whole library are available without an account, and none of it is sent to us.

The one thing your browser does tell us is its timezone (for example “Europe/London”), held in a small cookie, so the Puzzle of the Day turns over at your midnight rather than ours. It says nothing about who you are and is not used for anything else.

If you choose to make an account

An account is entirely optional, and exists for one reason: so the puzzles you have finished and the boards you have half-solved follow you between your phone and your computer. Making one costs an email address, which is used to send you a sign-in code and nothing else. There is no password to store, because we do not use passwords.

Once you are signed in, your boards, drafts and preferences are kept in your account instead of your browser - what this browser held is moved there when you sign in, and nothing of it is left behind on the device. We keep what you would expect and nothing more: the puzzles you finished, how long each took, how many hints and checks you used, the boards still in progress, the puzzles you are making in the Sudoku Maker, your solver preferences, the name you picked, and your timezone, so the daily reminder arrives in your own morning. You can read all of it back from your account page, and download your profile, your puzzles, your boards and your drafts as a file.

None of it is public. There are no leaderboards, no profiles, and no “solved by N players” on any puzzle. No other player can see what you have played or how fast you played it. Your times are shown to you, and to nobody else.

Signing in sets one cookie, which exists to keep you signed in. It is not used for advertising and not shared with anyone. If you opt in to the daily reminder email, every one of those carries a one-click unsubscribe link, and you can turn it off in your settings at any time.

What we collect

To keep the site running we use privacy-friendly, self-hosted analytics software that counts anonymous usage without cookies and without building any profile of you, and our servers briefly log IP addresses for the sole purpose of rate-limiting abuse and keeping the website available to everyone.

The contact form

If you write through the contact form, whatever you choose to put in it is received (such as your message and any address you give) and it is only used to respond to you.

Your rights

You have the right to access, correct, or delete any personal data held about you, and to lodge a complaint with your local data protection authority. If you play anonymously, the quickest way to erase your gameplay data is to clear your browser storage - we do not have a copy.

If you have an account, both rights are buttons rather than requests: your settings page will download your account as a file - your profile, every puzzle you finished and every board still in progress - and delete your account along with every result, board and setting attached to it. Deletion is immediate and cannot be undone. For anything else, reach out through the contact form.