Privacy policy

HanFlow is designed to teach Mandarin without requiring an account. Google synchronization and AI services are optional.

Effective date: 27 August 2026

Information stored locally

HanFlow stores learning answers, mastery estimates, preferences, downloaded model status, and optional provider configuration on your device. API keys remain in local application storage and are excluded from progress exports and Google synchronization.

Google account synchronization

If you explicitly connect Google synchronization, HanFlow requests only the drive.appdata scope. It stores per-device learning-progress snapshots, a random device identifier, a device label, and synchronization timestamps in the hidden Google Drive application-data folder.

HanFlow uses this information only to merge and restore your learning progress across your devices. It cannot access your ordinary Google Drive files. It does not sell, advertise with, or share Google user data with third parties.

HanFlow's use and transfer of information received from Google APIs adheres to the Google API Services User Data Policy, including its Limited Use requirements.

Optional AI providers

If you enable cloud AI, prompts needed for the selected learning feature are sent directly to the provider you configure. Google Drive synchronization does not send your progress to an AI provider. Offline learning and included adaptive activities remain available when cloud AI is disabled.

Retention and control

Local data remains until you reset HanFlow or remove the app's storage. Synchronized snapshots remain in Google Drive application data until you remove HanFlow's stored application data or delete your Google account. Disconnecting one device stops future synchronization on that device but does not erase progress from other devices.

Security

Google access tokens are short-lived and kept only in memory. HanFlow does not store Google passwords or OAuth refresh tokens. Data is transferred over HTTPS.

Advertising and purchases

After the free question allowances, HanFlow may use Google AdSense on the website and Google AdMob in the Android app. The advertising services may process IP addresses, which can estimate general location, product interactions, diagnostic information, consent choices, and device or account identifiers for advertising, analytics, measurement, and fraud prevention. Advertising never receives HanFlow learning answers or Google Drive content. Advertising requests are encrypted in transit.

Where required, Google's consent platform presents privacy choices before advertising is requested. Those choices can be reopened from HanFlow settings.

The Android app uses Google Play Billing for the optional one-time ad-free product. HanFlow stores an entitlement flag, verification time, and a one-way purchase-token hash with synchronized progress so the user's web session can honor the purchase. Payment details are handled by Google Play and are not received by HanFlow.

Contact

Questions or deletion requests: hanflow@davidkuc6.uk.