Privacy Policy for Sudoku

Last updated: 11 October 2026

This policy explains what information the Sudoku mobile app (“the app”) handles. It is written to describe exactly what the app’s code actually does.

The short version

The app is free, contains no advertising and no in-app purchases, and never sells your data. Most of what it stores stays on your own device.

It does use Google Firebase for three things: anonymous crash reporting, basic usage analytics that help us find bugs and see which features get used, and — only if you choose to use them — the optional online features (public leaderboard, challenges, and signing in with Google to back up your progress).

You can play the entire game, including the daily challenge, completely offline and without signing in to anything.

Information stored only on your device

The following is saved locally on your phone. If you never sign in with Google, it is never transmitted anywhere:

• Your in-progress and saved puzzles
• Your game statistics (games played, games won, best times, streaks)
• Your unlocked achievements
• Your daily challenge history
• Your preferences (board theme, sound, haptics, auto-notes, reminder time, and the display name you type in Settings)

This data is removed when you uninstall the app. You can also clear it at any time from the app’s own Settings (“Clear all saved data”), or from your device’s app settings. Deleting your account (see “Deleting your account” below) erases it too.

Analytics and crash reporting

The app includes Google Firebase Analytics and Firebase Crashlytics. These are used to fix bugs and understand which features people use. They are not advertising tools — the app contains no ad SDK, and no data is sold or shared with advertisers or data brokers.

Crash reporting (Crashlytics) collects diagnostic information when the app crashes or hits an error: the error and stack trace, the device model and operating system version, and the app version.

Usage analytics records a small, fixed set of in-app events:

• Which screen you are viewing (for example “Home”, “Game”, “Settings”)
• When a puzzle is started, including its variant and difficulty
• When a hint is used
• When a puzzle is completed, including whether it was won, the time taken, mistakes, and hints used
• When an achievement is unlocked (which achievement)
• When a setting is changed (which setting, not the value)

Firebase also automatically collects standard technical information such as an app-instance identifier, device and operating system details, app version, general region (derived from the IP address, not precise location), and session timing. Google processes this data as our service provider; see Google’s privacy policy: https://policies.google.com/privacy

The app does not request location permission, and does not access your contacts, photos, files, camera, or microphone.

Optional online features

These only transmit data if you choose to use them. Each is off or unused by default.

1. The public leaderboard. Off by default. If you switch it on, then when you finish a puzzle the app sends: the display name you chose (up to 24 characters — it does not have to be your real name), your completion time, mistakes, hints used, the difficulty, an identifier from Firebase Authentication, and the time of submission.

2. Challenge a Friend, and live 1v1 matches. When you create or join a challenge or a live match, the app sends the same categories of information as above, associated with that challenge or match code. In a live match, your progress (how many cells you have filled correctly, and your mistake count) is shared with your opponent while you play — that is the purpose of the feature.

Leaderboard entries and challenge results are publicly readable inside the app by other players. Do not put personal information in your display name.

3. Signing in with Google (optional). If you choose to sign in, Google provides the app with your name, email address, and profile information associated with that Google account. This is used to identify your account so your progress can be restored, and to claim your unique username.

4. Cloud backup (only if you sign in with Google). Once signed in, the app backs up the following to your account so it survives reinstalling: your display name, game statistics, unlocked achievements, daily challenge history, and app preferences. Your saved in-progress puzzles are not backed up.

Notifications

The optional daily reminder is scheduled locally on your device. It is off by default. It does not use push messaging, no notification token is created or sent to any server, and no information leaves your device for this feature.

Who processes this data

The app uses Google Firebase (Authentication, Cloud Firestore, Analytics, and Crashlytics), provided by Google LLC. Google processes this data as our service provider. Google’s privacy policy: https://policies.google.com/privacy

If you do not sign in with Google, the app uses Firebase anonymous authentication — a random identifier so the service can tell requests apart. It is not linked to an email address, phone number, or any other identity.

Children

The app is intended for people aged 13 and over and is not directed to children under 13. It does not knowingly collect personal information from children under

1. Because the display name is a free-text field shown to other players, we ask that players do not enter their real name or any other personal information there. If you believe a child under 13 has given personal information through the app, contact us (see “Contact” below) and we will delete it.

Your choices and rights

• Keep everything local: don’t sign in with Google, leave the leaderboard opt-in off (the default), and don’t use challenges. The game is fully playable this way.
• Turn off the reminder: Settings → Daily reminder.
• Change your display name: Settings, at any time.
• Delete your local data: Settings → “Clear all saved data”, or your device’s app settings.
• Delete your account and online data: Settings → “Delete account & online data” — see “Deleting your account” below.
• Depending on where you live, you may have additional rights over your personal data (for example under the GDPR or CCPA). Contact us to exercise them.

Deleting your account

In the app, go to Settings → Delete account & online data. You need an internet connection, and if you signed in with Google you are asked to confirm with that same Google account first. Step-by-step instructions, and how to ask for deletion if you can’t use the app, are on the account deletion page.

This permanently deletes:

• your Firebase Authentication account (anonymous or Google-linked), and the app’s access to your Google account;
• your cloud backup (stats, achievements, daily challenge history, preferences and display name) and your unique username;
• your leaderboard entries, the challenges you created, and your results in other players’ challenges;
• everything the app stores on your phone (see “Information stored only on your device”), with settings returned to their defaults and scheduled reminders cancelled.

Some records are not deleted:

• An anti-abuse counter — the time of your last score submission and a count of that day’s submissions, stored under your account’s random identifier with no name or contact details. It enforces the limit on submissions, so the app is not permitted to delete it; once your account is deleted it can no longer be linked to you.
• Live match records are stored under the match code rather than by player, so they can’t be looked up to delete individually. They are deleted automatically within 7 days of the match’s last activity.
• Other players’ results in a challenge you created are their data, not yours. They remain stored but can no longer be reached through the app once your challenge is deleted.
• Scores or challenges from an earlier identity — made before a reinstall, or before you signed in to a Google account already used on another device — were made under a different random identifier and can’t be matched to your account automatically. Contact us to have them removed.

Data retention

Locally stored data stays until you delete it or uninstall the app. Leaderboard entries, challenge records and your cloud backup are retained so those features keep working, until you delete your account or ask us to remove them. Live match records are automatically deleted after 7 days. Analytics and crash reports are not linked to your account and are kept according to Firebase Analytics and Crashlytics’ retention settings.

Security

Data in transit is encrypted using HTTPS/TLS. Access to stored leaderboard, challenge, and account data is restricted by server-side Firebase security rules.

Changes to this policy

If this policy changes, the “Last updated” date above will change and the revised policy will be posted at this same address.

Contact

Questions or deletion requests: chandradutt@kavachvpn.com (for deletion, include the display name or username you used and, if you signed in with Google, that account’s email address).