Summary
- No advertising SDKs, behavioral profiling, cross-app tracking, or sale of personal information.
- Firebase Analytics records a small, fixed set of product events and stable puzzle IDs.
- Gameplay and settings stay on your device by default.
- Leaderboards, friends, private races, notifications, iCloud sync, Sign in with Apple, puzzle updates, and voluntary tips are optional.
Information stored on your device
Open Sudoku stores app settings, the current puzzle, pencil notes, elapsed time, mistakes, hints used, downloaded puzzle packs, and gameplay history on your device. This information supports app functionality and is not used for advertising or tracking.
Product analytics
Firebase Analytics is always enabled, with no in-app opt-out, to help the developer understand which puzzles and features are useful. It records app lifecycle information and a limited set of events for puzzle opens and completions, hint use, lesson opens, completed shares, and the voluntary-tip funnel. Puzzle events include the stable puzzle ID and may include difficulty, how the puzzle was opened, input mode, automatic-candidate setting, elapsed seconds, mistake count, hint count, or lesson technique.
Analytics does not receive puzzle grids or solutions, entered digits, pencil notes, names, email addresses, Apple or Firebase account identifiers, or a Firebase user ID. The app does not link the IDFA-capable Analytics library, disables the identifier for vendor, disables automatic screen reporting, and denies advertising storage, advertising user data, and ad personalization. Analytics data is used for aggregate product decisions, not advertising.
Optional private iCloud sync
If you enable iCloud sync, Apple’s CloudKit service synchronizes gameplay progress through your private iCloud database. Sync is off by default and is independent from the optional Open Sudoku account. You can turn sync off or request deletion of the private iCloud copy from Settings while keeping local progress intact.
Optional Sign in with Apple
If you choose Sign in with Apple, Apple provides an account identifier and, on the first authorization, may provide the name or email address you choose to share. Open Sudoku uses Firebase Authentication to verify the Apple credential and maintain the optional account. This account is reserved for app functionality and is not required for gameplay, tips, puzzle updates, or iCloud sync.
You can sign out or delete the optional account from Settings. Account deletion removes community data, revokes the Apple authorization token, and removes the corresponding Firebase Authentication account.
Optional community features
When you first use a leaderboard, friend, or race feature, Open Sudoku creates a Firebase anonymous account and reserves a player name made only from curated words and numbers, such as CalmOtter4827. The app does not accept custom public names, biographies, chat, or other free-form public profile text. Exact-name friend search has no public or fuzzy directory.
Ranked play stores the canonical puzzle ID, generated player name, server-measured completion time, result status, and finish time. Private races also store participants, entry-count progress, winner, and expiration information. Friend relationships, requests, blocks, fixed-category reports, and a small in-app inbox are stored to provide those features. Other players can see generated names and ranked results; race progress is visible only to participants.
Anonymous Firebase credentials normally keep a guest profile available on the same installation, but device identifiers and guest credentials are not promised to survive deletion and reinstallation. Linking the profile to Apple is required for reliable account recovery and cross-device use. Linking preserves the Firebase user ID and existing community data.
Ranked grids and solutions are sent to a callable server function only to validate a finish. Client access is protected with Firebase App Check. Invite links contain a random secret, are not public matchmaking links, and expire after 30 minutes.
Optional race notifications
If you explicitly enable race notifications, Apple Push Notification service and Firebase Cloud Messaging process a device notification token so Open Sudoku can notify you about friend requests and private race activity. The token is removed from the community backend when you turn notifications off or delete the community account. The in-app inbox remains available without notifications.
Optional puzzle-pack updates
When you request or receive a puzzle catalog refresh, Open Sudoku contacts Google Firebase Firestore to download published puzzle packs. The downloaded puzzles are validated and stored for offline play. Firebase may process technical service data—such as IP address, app instance or installation identifiers, device and app version, and diagnostics—as needed to deliver, measure, and secure these services. Open Sudoku does not use Firebase Advertising.
Optional tip purchases
Voluntary tips are processed by Apple through StoreKit. Apple handles payment information; Open Sudoku does not receive your card or bank details. The app receives product and transaction status needed to complete and acknowledge the tip, and Firebase Analytics records the tip funnel and verified StoreKit transaction for product measurement. Tips are consumable and unlock nothing.
Puzzle sharing
If you choose Share Puzzle, iOS presents a system share sheet with the puzzle link and a locally rendered image. Open Sudoku sends this content only to the destination you select. The privacy practices of that destination apply after you share it.
Data sharing and retention
Personal information is not sold or shared with advertisers. Data is processed by Apple and Google Firebase for the services described above. Local history remains until you delete it in Settings or remove the app. Community profile data remains until you delete the guest or Apple-linked community profile; operational reports may be retained as needed for safety and abuse prevention. Analytics, iCloud, and purchase records follow the controls and retention policies of their providers.
Children’s privacy
Open Sudoku does not knowingly collect information from children for advertising, cross-app tracking, or profiling. Analytics is limited to the product events described above; optional platform services are governed by the user’s Apple account and device settings.
Service providers
Changes to this policy
If Open Sudoku’s data practices change, this page will be updated with a new effective date. Material changes will also be reflected in the app’s privacy disclosures.
Contact
For privacy questions or requests, email Petr Persianov at persianov.petr@gmail.com.