Privacy

Updated 26 October 2026. This notice describes the current web version of Ninefold Sudoku.

Your puzzles stay on your device

The app stores entries, pencil marks, colors, play history, completion times, hint counts, and mistake counts in your browser. Progress is not uploaded by the app. There is no account or cloud synchronization.

When the app connects

Opening the website downloads the app and its included puzzle library. Custom puzzle generation and proof checking run on your device using a downloaded WebAssembly engine. The web app does not send generation settings, entries, or play history to the server.

Website requests expose normal connection information, including your IP address and browser information, to the hosting service. The application server writes access logs containing request information. Hosting infrastructure may also keep operational logs. This app does not currently set a retention period for those infrastructure logs.

No advertising or analytics SDKs

The current app has no advertising, analytics SDK, or cross-site tracking code. Hosting infrastructure is separate from the in-app progress storage described above.

Offline files and backups

The app caches its files and published puzzles for offline use. Progress backups are files you choose to download or restore; the restore happens in your browser and does not upload the file. Keep backups private if you do not want others to see your play history.

Your controls

Use “Erase saved progress” under “App & storage” to remove this app’s saved plays from this browser. It does not erase backup files you have downloaded or server access logs. Your browser’s site-data controls can also remove progress and the offline library. Clearing one browser does not clear another device.

Contact

For privacy questions, contact sudoku@area9.dk. Information you choose to include in an email is shared with the support mailbox and its email provider.