Privacy Policy

This Privacy Policy describes how One Sudoku ("we", "us", or "our") handles your information when you use our applications for iPhone, iPad, and Android. We take your privacy seriously and have designed One Sudoku with a minimal data footprint.

You can play every Sudoku mode without an account. Signing in is optional. Guests can also view the leaderboards; a registered, verified account is required only to publish a score or hold a ranked position. If you never sign in, your game data stays on your device and we hold no personal information about you beyond the analytics and advertising data described in Sections 3 and 6. If you choose to sign in with Google, Apple, or an email address, we create an account for you and store your game progress on our cloud infrastructure so it can follow you across devices.

1. Information We Collect

a. Account information (only if you sign in)

If you create an account, we store:

• Your email address
• Your display name, if your sign-in provider supplies one
• A unique account identifier (Firebase UID) and the sign-in provider you used
• Account creation and last sign-in timestamps

What each sign-in method shares with us:

• Google: your email address, name, and profile photo URL from your Google account.
• Apple: your name and email address. If you choose "Hide My Email", Apple gives us an anonymous @privaterelay.appleid.com relay address instead of your real one, and we never see your actual email.
• Email & password: your email address. Your password is handled and stored in hashed form by Firebase Authentication — we never see or store your plaintext password.

b. Game data

Game progress — completed puzzles, streaks, statistics, and settings — is always stored locally on your device using standard platform storage (UserDefaults and local files on iOS, SharedPreferences and local files on Android).

If you are signed in, this game data is also synced to our cloud storage so you can continue on another device or restore it after reinstalling. It is linked to your account identifier. It contains no message content, no contacts, and no free-text you have written.

If you participate in the leaderboards, your chosen public leaderboard name, avatar, score, streak, and qualifying completion times are visible to other players. Your email address is never published on a leaderboard. Leaderboard entries can be reported in the app for review.

c. If you play as a guest

Without an account, your game data never leaves your device, except through iCloud Backup (iOS) or Google Backup (Android) — both controlled entirely by your own operating system settings, not by us.

d. What we never collect

• Your contacts, photos, files, or other device content
• Precise GPS location
• Payment or financial information

Note: our analytics and advertising partners collect certain data automatically, as described in Sections 3 and 6 below.

2. Accounts & Authentication

One Sudoku uses Firebase Authentication (a Google service) to sign you in. We support three optional methods: Sign in with Google, Sign in with Apple, and email & password.

Creating an account is entirely optional. It enables cross-device sync and lets you publish scores and hold a ranked position. Guests can play every puzzle mode and view the leaderboards without an account. You may sign out at any time, which stops all syncing, and you may delete your account permanently at any time — see Section 9.

3. Analytics (Google Firebase Analytics)

One Sudoku uses Google Firebase Analytics to understand how the app is used in aggregate, so we can fix problems and decide what to improve. Firebase Analytics automatically collects:

• A pseudonymous app instance identifier, which you can reset by reinstalling the app
• Device model, operating system version, app version, and language
• Approximate location at the country or region level, derived from your IP address
• Session information, such as when the app is opened and which screens are viewed
• In-app events, such as a puzzle being started or completed and which difficulty was chosen

We look at this data only in aggregate. We do not use it to identify you personally, we do not sell it, and we do not combine it with your account information to build a profile about you.

We may also receive anonymous, aggregated crash reports and performance data through Apple's and Google's built-in crash reporting, and through Firebase Crashlytics where enabled. This is used solely to fix bugs and improve stability.

For details, see Firebase's Privacy and Security page and Google's Privacy Policy.

4. Cloud Storage & Sync

Account information and, for signed-in users, synced game data are stored on Google Firebase infrastructure. Google acts as our data processor and processes this data on our behalf under its own security and privacy commitments.

Data is transmitted over encrypted connections (HTTPS/TLS) and encrypted at rest by Google. Access is restricted so that your synced game data is readable only by your own signed-in account and by us where necessary to operate and support the service.

5. How We Use Your Information

• To create and maintain your account and sign you in
• To sync and restore your game progress across your devices
• To understand aggregate app usage and improve the game
• To diagnose crashes and fix bugs
• To display ads that keep the app free
• To respond to your support requests

We do not sell your personal information, and we do not share your account information with advertisers.

6. Advertising (Google AdMob)

One Sudoku displays ads through Google AdMob to keep the app free. AdMob may collect:

• General location at the country or region level, estimated from the device's IP address
• App- or developer-bounded device identifiers used for functions such as frequency capping, aggregated reporting, and fraud prevention
• Advertising data, such as which ads were shown
• Product interaction, performance, crash, and other diagnostic data used to deliver, measure, and improve ads

One Sudoku requests non-personalized ads only. We do not use AdMob to track you across apps or websites, and the iOS app does not request App Tracking Transparency permission or access the IDFA. Non-personalized ads can still use contextual information and app- or developer-bounded identifiers for the limited purposes described above.

Where required by law, Google's consent form is shown before ads can load. If Google requires an ongoing privacy-choice entry point for your region, you can reopen it from Settings → Ad privacy options. Declining or withdrawing consent leaves the game fully playable without ads.

For details, see How Google uses information from sites or apps that use our services.

We do not share your account information with advertisers.

7. Third-Party Services

One Sudoku relies on the following third-party services. Each processes data under its own privacy policy:

• Google Firebase — authentication, cloud sync, and analytics. Firebase privacy
• Google AdMob — advertising. Google Privacy Policy
• Sign in with Apple — optional authentication. Apple Privacy Policy
• Apple App Store and Google Play — app distribution. Each may collect information in accordance with its own policy.

We do not integrate social media SDKs, marketing trackers, or data brokers.

8. Children's Privacy

One Sudoku is not directed at children under the age of 13, and we do not knowingly collect personal information from them. Because the app now supports optional account registration, users under 13 should not create an account without the consent of a parent or guardian.

The app contains no chat, direct messaging, social feed, likes, comments, or reposting. A registered player may choose a public name and avatar for the leaderboard; leaderboard content can be reported in the app. If you believe a child under 13 has created an account, please contact us at the address below and we will delete the account and its data promptly.

9. Your Rights & Data Deletion

You have the right to access, correct, export, and delete the personal data we hold about you, and to withdraw your consent at any time by signing out and deleting your account.

Deleting your account. Open the app and go to Settings → Account → Manage account & data → Delete account. This permanently removes your account and all game data synced to our servers. You can also email us at the address below from your account's email address and we will handle it for you. Full instructions are on our account deletion page.

Local data. Data stored on your device can be cleared at any time with "Reset All Progress" in the app's settings, or by uninstalling the app.

If you are located in the European Economic Area (EEA) or the United Kingdom, you also have the right to object to or restrict processing and to lodge a complaint with your local data protection authority. If you are a California resident, you have the right to know what personal information we collect and to request its deletion — we do not sell personal information.

To exercise any of these rights, contact us at the address below. We will respond within 30 days.

10. Data Retention

• Account and synced game data — retained for as long as your account is active. When you delete your account, it is removed from our production systems immediately and from backups within 30 days.
• Analytics data — retained in pseudonymous, aggregated form according to the retention period configured in Firebase, after which it is automatically deleted.
• Local device data — removed when you reset your progress in the app or uninstall the app.

11. International Data Transfers

Our service providers, including Google Firebase, process data on servers located in the United States and other countries. Where data is transferred out of the EEA or the UK, it is done under the safeguards provided by those providers, such as Standard Contractual Clauses.

12. Changes to This Policy

We may update this Privacy Policy from time to time. Any changes will be reflected on this page with an updated effective date. We encourage you to review this policy periodically. Continued use of the app after changes are posted constitutes your acceptance of the updated policy.

13. Contact Us

If you have any questions or concerns about this Privacy Policy, please contact us: