Privacy Policy

Last updated: July 13, 2026

1. Introduction

Welcome to Daily Sudoku Challenge ("dailysudoku.online"). We respect your privacy and are committed to protecting your personal data. This privacy policy explains how we collect, use, and safeguard information when you visit our website.

2. Data We Collect

We automatically collect the following information when you use our service:

  • IP address: Used to enforce our one-game-per-day rule and prevent abuse. Your IP is stored temporarily and associated with your game session for the current day only.
  • Browser fingerprint:A hash generated from your browser's canvas rendering. Used alongside IP address to identify unique players and prevent multiple game sessions per day. The raw fingerprint is never stored; only a one-way SHA-256 hash is retained.
  • Nickname: The display name you choose when starting a game. This is public and shown on the daily leaderboard.
  • Game data: Your score, completion time, number of errors, and difficulty level are stored to display the daily leaderboard.

3. How We Use Your Data

We use the collected data solely for:

  • Operating the daily puzzle and leaderboard
  • Preventing duplicate game sessions (one per day per player)
  • Displaying your nickname and score on the public leaderboard
  • Improving the game experience

4. Data Retention

All game data (scores, fingerprints, IP addresses) is automatically deleted at the start of each new day. We only maintain data for the current day's puzzle. Your nickname and browser fingerprint hash may be retained to identify returning players across sessions.

5. Third-Party Services

  • Google AdSense: We use Google AdSense to display advertisements. Google may use cookies and web beacons to serve ads based on your prior visits to our website or other websites. You can opt out of personalized advertising by visiting Google Ad Settings.
  • Neon Database: Game data is stored on Neon PostgreSQL servers located in the United States.
  • Vercel: Our website is hosted on Vercel. Vercel may collect standard web server logs including IP addresses.

6. Cookies

We use browser localStorage to store your nickname and game completion status for convenience. These are stored locally on your device and are not transmitted to our servers. Third-party cookies may be set by Google AdSense for advertising purposes.

7. Your Rights

Depending on your jurisdiction, you may have the right to access, correct, or delete your personal data. Since game data is automatically deleted daily, most data is ephemeral. To request deletion of your persistent data (nickname, fingerprint hash), please contact us.

8. Children's Privacy

Our service is not directed to children under 13. We do not knowingly collect personal information from children. If you believe a child has provided us with personal data, please contact us and we will promptly delete it.

9. Changes to This Policy

We may update this privacy policy from time to time. Changes will be posted on this page with an updated "Last updated" date.

10. Contact

If you have questions about this privacy policy, please contact us.