Privacy Policy

Last updated: October 21, 2026

This policy says what SudokuSudoku does with information when you play, when Google measures or advertises, and when you send a message.

Playing does not need an account

You do not register. Puzzle progress, settings, your own stats, and the skill ladder are stored in local storage on your device. They are not sent to a server, and they are not cookies. Clearing the site's data in your browser deletes them. Using a different browser or device starts fresh. Anonymous community stats, described next, are the exception, and only when sharing is on.

Anonymous play stats

The public stats page shows how long puzzles take and how often they are solved, given up, failed, or left unfinished. That comes from plays on this site. Sharing is on unless you turn off "Share anonymous play stats" in Settings.

A shared play sends the puzzle level, whether it is the daily, the UTC date for a daily, a hash of the puzzle seed or of the givens, the outcome, the active seconds on the timer (pause is not counted), mistakes, how many hints you used and the hardest technique among them, whether you used notes, and a device class taken from the width of the window: phone, tablet, or desktop. It does not send the puzzle itself, the solution, your name, your IP address, or the browser's user agent string. The server does not store those, and it does not build a fingerprint.

The browser keeps a random id in local storage under the key sudoku-anon-id. It is not a cookie. It exists so the same puzzle is not counted twice for the same browser. Turn "Share anonymous play stats" off and that id is deleted, along with any stats waiting to be sent. Clearing site data for sudokusudoku.com deletes it too. A new id, if you turn sharing back on, does not reconnect to the old one.

That id is storage on your device, and the stats are not required to play, so it is not strictly necessary. In the European Economic Area, the United Kingdom, and Switzerland the game does not create the id and does not send stats until Google's consent message reports that analytics storage is granted. That is the same choice as Analytics on the other pages. This page does not load that message. Use Privacy choices on another page if you want to change it. Outside those countries the Settings toggle is the control, and it starts on.

A puzzle you close and resume is the same play. Replacing it with a new game, or coming back to find the saved game gone, marks it abandoned. Hitting the four-mistake limit does not, until you leave that game, because undo continues it. A start with no finish after 24 hours is marked abandoned on the server. Groups with fewer than 20 finished plays are not shown.

Contact form

If you use the contact form, the name, email address, and message you enter are emailed to me so I can read them and reply. A hidden field is there for spam bots. If that field is filled in, the message is discarded.

The form uses Cloudflare Turnstile. Turnstile checks that a person submitted it. That check sends a token, and Cloudflare may receive connection details such as your IP address, under Cloudflare's privacy policy. I do not publish your email address on the site.

If mail delivery is not configured, the form says so and does not send anything.

Google Analytics and AdSense

This page does not load Google Analytics, the AdSense script, or the Funding Choices consent message. The game and the other pages load Google Analytics (measurement ID G-TFNKPH6DNY) and the Google AdSense script (publisher ca-pub-9345046210950956). Google may use cookies to measure visits and to serve and measure ads. How Google uses data from sites that use its services is described at Google's partner sites policy. Ad settings are at Google's Ad Settings. You can also install the Analytics opt-out add-on.

Visitors in the European Economic Area, the United Kingdom, and Switzerland get a consent message from Google's certified consent management platform. Consent Mode defaults on those visits are denied for ad storage, ad user data, ad personalization, and analytics storage until you choose. In other regions those defaults are granted. A visit is not, by itself, consent to cookies.

Privacy choices, in the footer of the other pages, reopens Google's consent message. It is not on this page. On a page that does not load the ad script, such as the links page, the control tells you to open the home page and use it there.

What this site does not do

The site is served globally through Cloudflare. It is not hosted in one country. Your saved game stays on the device. The anonymous play stats above are the gameplay fields stored on Cloudflare's D1 database, and only when sharing is on. Messages you send through the contact form are delivered as email and may be processed by Cloudflare and by whatever mail provider receives them.

The links page points at other people's sites. Their privacy practices are their own.

Children

The puzzles are fine for children. I do not knowingly collect personal information from anyone under 13. If a child sent a message through the contact form, use that same form to ask me to delete it.

Asking about your information

The personal information I receive is whatever you put in the contact form. You can ask to see it, correct it, or delete it by writing again through the contact form. There is no marketing list to opt out of.

Changes

If this policy changes, the date at the top changes with it.