Privacy Policy
For the Delzo puzzle games, including Sudoku – Classic & Variants.
Last updated 13 September 2026.
What stays on your device
Saved games, pencil marks, settings, your daily streak, completion times, campaign progress and cached daily puzzles are stored only on your phone. They are never uploaded, and deleting the app deletes them.
What leaves your device
Advertising — Google AdMob
Unless you have bought the ad-free option, the games show adverts. AdMob receives your device's advertising identifier, IP address, device type and operating system, and records which adverts were shown or tapped. Whether those adverts are personalised depends on the choice you make the first time you open the game, and you can change it at any time — see Your choices.
Usage statistics — Google Analytics for Firebase
We record how the games are played so we know what to improve. This is tied to a random app instance identifier, not to you. The complete list of events is:
| Event | What it records |
|---|---|
app_open | the app was opened |
puzzle_start | mode, difficulty, variant, grid size |
puzzle_complete | time taken, hints, mistakes, difficulty, variant, hardest technique |
puzzle_abandon | time spent, cells left, difficulty, variant |
hint_used | which technique, whether an advert was watched |
ad_impression, reward_earned | that an advert was shown or a reward given |
paywall_shown, remove_ads_purchased, purchase_failed | that the ad-free option was offered, bought, or failed |
daily_streak | length of your daily streak |
cross_promo_tapped | which of our other games you tapped |
Two properties are also attached: which variant you play most, and whether you have removed adverts. Firebase additionally collects standard technical information such as device model, operating system version and approximate country. None of it identifies you by name.
Crash reports — Firebase Crashlytics
When the app crashes we receive the error, the stack trace, the device model and operating system version, and what the app was doing at the time. This is used only to fix the fault.
Purchases — RevenueCat
If you buy the ad-free option, RevenueCat records the purchase against an anonymous identifier so it can be restored on your other devices. Payment is handled entirely by Apple or Google — we never see your card details, name or billing address.
Your choices
- Adverts. In the European Economic Area and the United Kingdom you are asked before any personalised advert is loaded. Reopen that choice at any time in Settings → Privacy choices.
- Tracking on iPhone and iPad. iOS asks separately for permission to track. Declining is fine — the game is identical, the adverts are simply not personalised. Change it in iOS Settings → Privacy & Security → Tracking.
- Usage statistics. If you decline consent, analytics collection is switched off rather than merely hidden.
- Advertising identifier. You can reset or limit it in Android Settings → Privacy → Ads, or iOS Settings → Privacy & Security → Tracking.
- Remove adverts. Buying the ad-free option stops advert loading altogether, and with it everything AdMob would have received.
Deleting your data
Uninstalling the app removes everything held on your device. To have usage statistics and crash reports associated with your installation deleted, write to the address below with the approximate date and the device you used, and we will ask Google to delete them. Purchase records are kept for as long as tax and refund rules require.
Children
These games are not directed at children under 13, and we do not knowingly collect information from them. If you believe a child has provided information, write to us and it will be removed.
Who else receives data
Only the services named above: Google (AdMob, Analytics for Firebase, Crashlytics) and RevenueCat. We do not sell data, and there is no other recipient. Their own policies apply in addition to this one: Google, RevenueCat.
Changes
If this policy changes, the date at the top changes with it. Material changes will be announced in the app before they take effect.