Privacy Policy

Lingo Books

Last updated: November 4, 2026

This privacy policy explains what information the Lingo Books app ("the app") for iOS and Android collects, how it is used, and what choices you have. The app is developed by Mykola Mylashko ("I", "me"). By using the app you agree to this policy.

1. Data that stays on your device

Most of what you do in the app never leaves your device:

- Books you import (EPUB, PDF, TXT and other files) and their text.

- Your dictionary, saved words, flashcards and their review history.

- Reading progress, bookmarks, streaks, goals, achievements and settings.

- Translations and language detection. They run on your device with Google ML Kit; the text you read or translate is not sent to me or to Google. Translation models are downloaded from Google once and then work offline.

- Text-to-speech, which uses the speech engine of your device.

- Reminders, which are scheduled locally on your device.

I do not have access to this data. It is deleted when you delete the app. If your device backs up app data (iCloud or Google backup), the backup is handled by Apple or Google under their own policies.

2. Data collected automatically

To understand how the app is used, fix errors and process purchases, the app uses the following third-party services. They collect data that does not include your name, email or the content of your books.

Firebase Analytics (Google): anonymous usage events, such as app opens, onboarding steps, reading sessions (book from the built-in catalogue, duration), flashcard sessions, paywall views and subscription events, plus device model, operating system version, app version, language, country/region derived from the IP address, and an app instance identifier. On Android, the advertising ID may be read by the Firebase SDK for analytics; it is not used for advertising. The app shows no ads.

Firebase Crashlytics (Google, Android version): crash reports and error diagnostics (stack trace, device model, OS version, app version, and technical context such as the language of a failed translation download or the file type of a failed import).

Firebase Storage and Firebase App Check (Google): download the books of the built-in catalogue and, on Android, verify with Google Play Integrity that requests come from a genuine copy of the app. These requests contain technical device information but no personal content.

RevenueCat: manages subscriptions and in-app purchases. It receives an anonymous app user ID, purchase and subscription status, transaction details from the App Store or Google Play, device type, OS version and country. I never receive your payment card details; payments are processed by Apple or Google.

Privacy policies of these services:

- Google / Firebase: https://policies.google.com/privacy and https://firebase.google.com/support/privacy

- RevenueCat: https://www.revenuecat.com/privacy

- Apple: https://www.apple.com/legal/privacy/

- Google Play: https://policies.google.com/privacy

3. How the data is used

The collected data is used only to:

- provide and improve the app and its features;

- find and fix crashes and errors;

- process subscriptions and restore purchases;

- protect the app's backend from abuse.

I do not sell your data, do not use it for advertising, and do not share it with anyone other than the service providers listed above, who process it on my behalf.

4. Security

All data sent by the app is encrypted in transit (HTTPS). No method of transmission or storage is 100% secure, but I use reputable providers and collect as little data as possible.

5. Data retention and deletion

The app has no user accounts. Data on your device is removed when you delete the app. Analytics data in Firebase is kept for up to 14 months; crash reports are kept for up to 90 days. To ask for deletion of data linked to your app instance, write to the email below. You can manage or cancel subscriptions in your App Store or Google Play account settings.

6. Children

The app is not directed at children under 13, and I do not knowingly collect personal information from them. If you believe a child has provided personal information, contact me and I will delete it.

7. Your rights

Depending on where you live (for example, under the GDPR or CCPA), you may have the right to access, correct or delete your personal data, or to object to its processing. To use these rights, contact me at the email below.

8. Changes to this policy

I may update this policy from time to time. Changes take effect when they are posted on this page, and the date at the top will be updated.

9. Contact

If you have any questions about this privacy policy, contact me at flowing-bytes@proton.me.