Privacy Policy

The short version

You can play every mode on Sudokusama without signing up, and without giving us your email address. We do not run analytics or tracking pixels, and we never sell your data. Most of what the site remembers — your saved games, streaks and best scores — never leaves your own browser. If you choose to sign in with Google or Facebook, or to subscribe to our newsletter, we will hold your email address — those are covered below.

What stays on your device

The following is stored in your browser's local storage. It is not sent to us and we cannot read it:

• Your in-progress games, so you can close the tab and continue later
• Daily Challenge and Daily Mini streaks, and whether you finished today's puzzle
• Your Time Rush best scores
• The display name and character you last chose
• Your light/dark theme preference

Clearing your browser storage erases all of it permanently.

If you create an account

An account is optional. If you make one, we store:

• Your username and a hashed password (hashed with bcrypt — we never store or see your actual password)
• Your completed games: difficulty, time taken, number of mistakes, whether you won, and the date — used to show your profile stats and the Daily Challenge leaderboard

Signing up this way requires no email address, phone number, real name, address, or payment details. If you want your account and its stats deleted, email us and we will remove them.

Signing in with Google or Facebook

We are adding the option to sign in using your Google or Facebook account. If you choose to use it, that provider sends us a limited profile — your email address, your name, and possibly your profile picture — which we use to create and identify your account. We only ever receive what you approve on the provider's consent screen, and we never receive your Google or Facebook password. You can always create a plain username-and-password account instead, or play with no account at all.

Newsletter

We are adding an optional email newsletter. If — and only if — you actively subscribe, we store your email address for the purpose of sending it. We will not subscribe you automatically because you made an account, we will not sell or rent your address, and we will not hand it to advertisers. Every newsletter includes a one-click unsubscribe link, and you can ask us to erase your address at any time by emailing sudokusama@gmail.com.

Multiplayer

In a multiplayer room, the display name and character you pick are visible to the other players in that room — so choose a name you are comfortable sharing. Rooms live only in the memory of our realtime server and are discarded when the game ends; we do not keep a record of them.

Cookies

If you sign in, we set a single session cookie so the site knows you are logged in. It is strictly necessary for the login to work and is removed when you sign out. We do not use cookies for analytics.

Advertising

Sudokusama does not display ads today. We intend to introduce advertising through Google AdSense to keep the site free. When we do, Google and its partners may use cookies to serve ads based on your prior visits to this or other websites. You can opt out of personalised advertising in Google Ads Settings, and read how Google uses data from sites that use its services at policies.google.com/technologies/partner-sites. Visitors in the EEA and UK will be asked for consent before any personalised ads are shown. We will not run ads on our Sudoku for Kids page.

Children

Our Sudoku for Kids page is designed for younger players. It requires no account and collects no personal information, and we do not serve personalised advertising there. If you believe a child has given us personal information, email us and we will delete it.

Who else is involved

We rely on a small number of providers to run the site:

• Vercel — hosts the website and processes standard server request logs
• Railway — hosts our database and the realtime multiplayer server
• Google and Facebook — only if you choose to sign in with them (see above)
• An email delivery provider — only if you subscribe to the newsletter, to deliver it
• Google AdSense — advertising, once introduced (see above)

Your rights

Depending on where you live, you may have the right to access, correct, or delete the data we hold about you, to object to how we use it, or to withdraw consent you previously gave. The only data we hold is tied to an optional account or a newsletter subscription — email us at sudokusama@gmail.com and we will action it.

Changes

If we change this policy — for example when advertising goes live — we will update the date at the top of this page.

Contact

Questions about privacy? Email sudokusama@gmail.com, or see our contact page.