Effective date: October 15, 2026
VietQuest ("the App", "we", "us") is developed and operated by an independent individual developer. This Privacy Policy explains what information the App collects, how it is used, and the choices you have. By using VietQuest, you agree to the practices described here.
Your learning progress — streaks, completed levels, scores, settings, and similar data — is stored directly on your device using on-device storage. Your learning progress is never transmitted to us unless you choose to create an account (see 1.3); a few technical services described in sections 1.4, 1.7, 1.8 and 1.9 (subscription status, ads, crash reporting) do receive technical data without an account. Your phone's own backup service (iCloud or Google backup) may include the App's data if you have turned device backup on. The free version needs an internet connection to run its lessons and ads; Premium subscribers can also use the App offline. To show your daily practice reminder, the App can schedule a local notification on your device; this reminder is created and delivered by your device, and no notification token or push-notification data is sent to us. Besides the daily reminder, the App can schedule an optional evening nudge to protect your streak and, if you are on the Leaderboard, a nudge when a friend passes you; both are also created on your device.
The first time you open VietQuest, we ask what year you were born. This is used only to determine, on your device, whether you are under 13 — nothing more precise than that is ever asked or recorded. Your birth year itself is never transmitted to us or stored anywhere; the check uses the year only, so it is approximate and errs on the side of caution (for example, anyone born 13 calendar years ago is treated as under 13); only the resulting under-13/13-or-older result is saved, locally on your device, so the App can remember your answer the next time you open it. The answer is asked once, during first-run setup, and cannot be changed inside the App afterwards (this protects younger learners). If you entered it by mistake, on Android clear the App's data in your device settings (Settings > Apps > VietQuest > Storage), and on iPhone delete the App and install it again, then answer again. If your device restores app backups automatically, the old answer may come back after a reinstall; clearing the App's data (Android) avoids this. If you tell us you're under 13, VietQuest automatically: disables account creation and sign-in (see 1.3) so no email or other account data is ever collected from you, and switches advertising to Google's child-directed mode, which turns off ad personalization and restricts ad content (see 1.7). A few technical services still run for every user, including children: the subscription-status service (with an anonymous identifier), crash reporting, the App Check integrity signal and the update check (see 1.4, 1.8 and 1.9). Users who installed VietQuest before this screening existed were not asked and are not affected retroactively.
Most of VietQuest's learning content can be used without ever creating an account. If you choose to create an account — by signing in with Google, signing in with Apple, or registering with an email address and password — we collect and store the following via Google Firebase (Authentication and Cloud Firestore):
Signing in and creating an account is optional for using the App (buying Premium does require an account with a verified email address, or a Google or Apple sign-in, so that your purchase can be restored; signing out turns Premium off on that device until you sign in again), and is not available at all if you told us you're under 13 (see 1.2). If you never sign in, none of this data ever leaves your device.
If you subscribe to VietQuest Premium, our subscription management provider, RevenueCat, is started when the App opens (with an anonymous identifier, even if you never subscribe) so the App can check whether Premium is active. If you subscribe, RevenueCat receives and stores your purchase and subscription status (e.g. active/expired, renewal date) together with your account ID, so the app can verify your Premium entitlement across devices. VietQuest itself never sees or stores your payment card details — these are handled entirely by Apple or Google Play.
If you use the "Tone Match" pronunciation practice feature, the pitch of your voice is analyzed on your device. We never upload your voice recordings to our own servers. However, to check what you said, the recording is also passed to your device's built-in speech recognition (see 1.6). Recordings are only used to produce a score or check your answer.
Our Pronunciation Practice feature, Tone Match, and the "Speak" button used to answer by voice in lessons and stories use your device's built-in speech recognition (provided by Apple on iOS or Google on Android) to check how closely your spoken words match the target pronunciation. Depending on your device and operating system settings, this may involve your voice recording being processed by Apple's or Google's speech recognition service, which operates under its own privacy policy. We do not store these recordings on our own servers; the recording is only used to generate a score or to check your spoken answer. Temporary audio files may remain in the App's cache on your device until your phone clears them.
Free-tier (non-Premium) users may see ads served by Google AdMob. AdMob may collect your device's advertising identifier (IDFA on iOS, or Android Advertising ID) to serve and measure ads. On iOS, we ask your permission through Apple's App Tracking Transparency prompt before using your advertising identifier. If you allow it, AdMob may use that identifier to show ads that are more relevant to you; if you decline, you still see the same amount of ads, but they are non-personalized. On Android, outside the European Economic Area, the United Kingdom and Switzerland, AdMob may personalize ads using the Android Advertising ID by default; you can reset it or opt out of ad personalization at any time in your Android settings (Settings > Privacy > Ads). Where consent is required by law, we only request ads according to your choice in Google's consent form. The advertising software is started only after you finish the first-run setup, which includes the age question (see 1.2). If you told us you're under 13 (see 1.2), we never show the tracking prompt, ads are always non-personalized and content-restricted, and this identifier is not used to personalize ads regardless of any other setting. Premium subscribers never see ads. The advertising software may still start in the background on a Premium device (for example to read your consent status), but no ads are shown to Premium subscribers.
We do not use Facebook SDK or Google Analytics. Apart from the usage events described in section 1.10 and the technical data in sections 1.8 and 1.9, we do not run any analytics service of our own.
Like most online services, our service providers (Google Firebase, Google AdMob, RevenueCat, Sentry) automatically record certain technical information in server logs when the App communicates with their servers — such as IP address, device/OS type, and app version. This is standard technical logging used for operating, securing, and troubleshooting the service, and is not used to build an advertising profile of you beyond what is described in section 1.7. Firebase App Check may also send device-integrity signals to Google, which helps us tell genuine copies of the App from abusive traffic. To check that you are online, the App may make simple connection tests to Google and Apple servers (when you open or return to the App and, in the free version, before new lesson questions), and it contacts Expo's update service to check for app updates; these requests expose your IP address to those providers.
If the App encounters an unexpected error, technical diagnostic information (device type, OS version, app version, and the error details/stack trace) is automatically sent to our crash-reporting provider, Sentry, so we can identify and fix bugs. Sentry may also receive basic app-session information (such as app start and end) and a short trail of recent in-app events leading up to an error. We do not send your personal messages, voice recordings, or learning answers to Sentry.
If you are signed in, VietQuest records basic usage events, such as which lesson was completed or skipped, which screen offered Premium, the outcome of a purchase attempt, referral and achievement milestones, and reminder choices, using fixed event names and simple values such as a level number or a plan name. They are stored in our Google Firestore database together with your account ID, so we can see which lessons are too hard or too long and whether the app is working as intended. These events never contain free text, voice recordings or your answers. If you do not sign in, no usage events are recorded.
We do not sell your personal information to anyone, and we do not use your learning progress or voice data for advertising purposes.
We do not share your data with any other third party, and we do not sell it.
Our service providers (Google Firebase, Google AdMob, RevenueCat, Sentry) may process and store data on servers located outside your country of residence, including in the United States or other countries where they operate data centers. By using the App, you understand that your information may be transferred to and processed in countries that may have different data protection laws than your own.
If you are located in Vietnam, your personal data is processed in accordance with Decree 13/2023/NĐ-CP on Personal Data Protection in addition to the practices described throughout this Policy. By creating an account (section 1.3), you consent to the collection, processing, and — as described in section 3.1 — cross-border transfer of your personal data for the purposes described in section 2. You may withdraw this consent at any time by deleting your account (section 4.1) or by contacting us at the email in section 13, and you may exercise the other rights listed in section 4 in the same way.
Locally stored data remains on your device until you delete the app. Cloud-synced data remains linked to your account until you delete your account or ask us to delete it.
Depending on your location, you may have the right to:
You can permanently delete your VietQuest account at any time, directly within the app:
This deletes from our systems: your sign-in account and email address, learning progress, streak history, gem balance, your Leaderboard entries (the current week and up to the previous 52 weeks; older weekly entries, if any, can be removed on request), your saved Leaderboard nickname and hide setting, the feedback messages you submitted, your usage events (see 1.10), your public referral-code lookup entry and your list of invited friends, and your registered devices. This action cannot be undone. Deleting your account does not cancel an active subscription: cancel it in your Apple ID or Google Play subscriptions to stop future charges. If a part of the cleanup cannot be completed (for example because of a network problem), email us at the address in section 13 and we will remove the rest by hand.
To help keep the referral program consistent (other users' referral records and reward payments refer to these records) and to keep billing records accurate, a few small technical records are kept after deletion, linked only to your former anonymous account ID and containing no email address, name or nickname: the record of gems already granted, your referral program record (invite code, the code you redeemed, the account ID of the person who invited you, and the reward-paid markers, which are needed so that other users' referral records and reward payments stay consistent and are not paid twice), a Leaderboard rate-limit marker, a moderation marker if your Leaderboard access was ever restricted for an offensive nickname, any older referral-reward records from an earlier version of the referral program (these contain only anonymous account IDs), and your subscription entitlement record (which stores whether your Premium subscription is active). Once your sign-in account is deleted, these cannot be used to sign in or to identify you from the App. If you would like them removed as well, email us at the address in section 13 and we will delete them by hand within 30 days (removing the moderation marker, if one exists, also lifts the Leaderboard restriction). Purchase records held by Apple, Google or RevenueCat follow their own policies.
For security, deleting an account may ask you to confirm your identity first: Google and Apple users sign in again with their provider, and email users type their password in the App.
To exercise any other rights above, email us at the address in section 13 — we will respond and act on your request within a reasonable time.
VietQuest is not directed or marketed to children under the age of 13. As described in section 1.2, the App asks every new user what year they were born and automatically disables account creation/sign-in and switches to child-directed, non-personalized advertising for anyone who tells us they are under 13 — we do not knowingly collect email addresses, nicknames, or other account data from a user who tells us they are under 13. This screening relies on what you tell us; it cannot independently verify your age. Accounts and Premium subscriptions are available only to users aged 13 or older. If we become aware that we have inadvertently collected personal information from a child under 13 without appropriate consent, we will delete it promptly. If you believe this has happened, please contact us at the email below.
We use industry-standard practices (including Firebase Security Rules and encrypted connections) to protect the data we hold. However, no method of transmission or storage is 100% secure, and we cannot guarantee absolute security.
The free version of VietQuest shows ads from Google AdMob. On iOS, the App asks for your permission through Apple's App Tracking Transparency prompt (once, before the first ad). If you allow tracking, ads may be personalized; if you decline, ads are non-personalized. You can change this at any time in Settings > Privacy & Security > Tracking. On Android, ads follow Google's consent form where it is required and your Android advertising settings otherwise (see 1.7). If you are in the European Economic Area (EEA), the United Kingdom or Switzerland, you first see a consent form from Google where you can accept or refuse the use of data for ads. Because the consent status is checked when the App starts, the form may also appear to Premium subscribers in these regions, although Premium subscribers never see ads. Even for non-personalized ads, AdMob may use device identifiers to deliver ads, limit how often you see them, measure results and prevent fraud.
We process your personal data on these legal bases:
You have the right to access, correct, delete and export your data, to restrict or object to its processing, and to complain to your local data protection authority. Our service providers may process data outside your country, including in the United States, under the safeguards described in their own privacy policies (for example standard contractual clauses). To use a right, email us at the address in section 13.
We do not sell your personal information. If you allow tracking on iOS, or consent to personalized ads where asked, AdMob may use your advertising identifier for personalized ads, which some laws treat as sharing for cross-context behavioral advertising; you can decline or change this at any time as described in section 8. California residents may ask what personal information we hold about them, ask us to delete or correct it, and will not be treated differently for using these rights. We do not collect sensitive personal information. To make a request, email us at the address in section 13.
If you still have the App, use Settings > Delete account (see section 4.1). If you have uninstalled the App or cannot sign in, email support.vietquest@gmail.com with the subject "Delete my VietQuest data", from the email address linked to your account (or tell us the nickname you used). We will confirm your request and delete your account and cloud data within 30 days. Technical records that the in-app deletion keeps (see section 4.1) are deleted by hand on request, within the same 30 days. Purchase records held by Apple or Google follow their own policies.
We may update this Privacy Policy from time to time. Material changes will be reflected by updating the "Effective date" above. Continued use of the App after changes take effect constitutes acceptance of the updated policy.
Your use of the App is also governed by our Terms of Use.
If you have any questions about this Privacy Policy, please contact us at:
support.vietquest@gmail.com