Privacy Policy
Last updated: April 19, 2026
At SudokuW, your privacy matters. This Privacy Policy explains what information we collect, how we use it, and your rights regarding that information. SudokuW is a free, anonymous online Sudoku game - we are committed to collecting as little data as possible while still providing a great experience.
Information We Collect
We collect minimal information necessary to operate the service. We do not require registration, email addresses, or passwords to play.
Automatically Collected
- Anonymous User ID - A randomly generated identifier (UUID) stored in a cookie on your browser. This is not linked to your real identity, email, or any personal information.
- Game Progress - Your Sudoku board state, completion times, and level progression are stored locally in your browser and on our servers to save your progress.
- Multiplayer Rating - If you play multiplayer games, an Elo rating is calculated and stored to match you with similarly skilled players.
Voluntarily Provided
- Display Name - You may optionally choose a display name for daily challenge leaderboards and multiplayer games. This is entirely optional and can be any name you choose.
We do not collect your real name, email address, phone number, physical address, payment information, or any other personally identifiable information.
Cookies
We use a single, essential cookie to operate the service:
| Cookie | Purpose | Duration | Type |
|---|---|---|---|
sudoku_anon_id |
Stores your anonymous user identifier so we can save your game progress and display name across visits. | 5 years | Essential / Functional |
Browser Local Storage
We use your browser's local storage (not cookies) to save game data directly on your device:
- Saved game board state for regular Sudoku, daily challenges, and journey mode
- Your preferred multiplayer difficulty setting
- Daily challenge participation status
How We Use Your Information
The information we collect is used solely to provide and improve the game:
- Save and restore your game progress across sessions
- Display your chosen name on leaderboards and in multiplayer games
- Calculate and display multiplayer ratings for fair matchmaking
- Track daily challenge completion and journey level progression
- Maintain multiplayer game state during live matches
Third-Party Services
We use minimal third-party services:
- Fonts - Inter and Plus Jakarta Sans are self-hosted on our servers. No third-party font service is used.
We do not use any analytics services (such as Google Analytics), advertising networks, tracking pixels, social media plugins, or any other third-party tracking tools. We do not sell, share, or transfer your data to any third party for advertising or marketing purposes.
Data Retention
- Anonymous User ID cookie: Retained for up to 5 years, or until you clear your browser cookies.
- Local storage data: Retained until you clear your browser data.
- Server-side game data (daily challenge scores, journey progress, multiplayer ratings): Retained indefinitely to preserve your progress. Since this data is linked only to an anonymous ID, it cannot be traced back to you personally.
Data Security
We implement the following measures to protect your data:
- Content Security Policy (CSP) headers to prevent cross-site scripting and injection attacks
- HttpOnly cookies that cannot be accessed by client-side scripts
- Secure cookie transmission over HTTPS in production
- Input validation and sanitization on all user-submitted data
- No storage of passwords, payment data, or sensitive personal information
Children's Privacy
SudokuW is a general-audience puzzle game that does not knowingly collect personal information from children under the age of 13 (or the applicable age in your jurisdiction). Since we do not collect personally identifiable information from any user, there is no age-restricted data to manage. If you are a parent or guardian and believe your child has provided personal information, please contact us.
Your Rights
Depending on your location, you may have certain rights regarding your data:
- Access - You can view your locally stored data in your browser's developer tools (Application > Local Storage and Application > Cookies).
- Deletion - You can delete all locally stored data by clearing your browser cookies and local storage. Server-side anonymous data can be deleted upon request.
- Opt-out - Since we do not track or profile users, there is no tracking to opt out of. You can block cookies entirely, though this will prevent game progress from being saved across visits.
- Portability - Since we store minimal, anonymous game data, we can provide an export of your server-side data upon request.
Changes to This Policy
We may update this Privacy Policy from time to time to reflect changes in our practices or for legal, operational, or regulatory reasons. When we do, we will update the "Last updated" date at the top of this page. We encourage you to review this page periodically. Your continued use of SudokuW after any changes constitutes acceptance of the updated policy.
Contact Us
If you have any questions about this Privacy Policy or wish to exercise your data rights, please contact us through our Contact page.