Privacy Policy

Open Book app · Effective 25 October 2026

Open Book is an app for reading books and learning English words. It runs on your device: the developer does not collect your name, email or learning data, and shares or sells no data at all. The only exception is the check of purchased books, described in section 1.

1. What the app collects

• No account; the app never asks for your name, email, phone number or date of birth.
• No advertising and no third-party analytics or tracking tools.
• The app sends none of your learning data to any server of the developer.
• Only when you download a book of the “Học nâng cao” package, the app sends your Apple-signed purchase to the app’s book server to check that you bought it. The server does not keep the signed purchase. It keeps only the original transaction ID issued by Apple (which contains no name, email or payment details), a hash of a private key the app creates on your device, the public key the app uses to prove to the server that it is the genuine app (Apple’s App Attest), and the times of downloads. Its only purpose is to let one purchase be used on up to 5 devices and 30 downloads a day, and to stop downloads once Apple reports the purchase as refunded. A device stays on the list for 180 days after its last download; download times are kept for 24 hours. This data is not used for advertising or tracking and is not shared with anyone. Payment is handled by Apple; the app never sees your card details.
• The app does not request access to location, contacts, photos, microphone or camera.

2. Data stored on your device and in your iCloud

So that you can pick up where you left off, the app stores on your device: saved words and their review schedule, reading position, finished sections, bookmarks, and reading settings.

If the device is signed in to iCloud, the app syncs this data (except text size, line spacing and voices, which are per device) through your own iCloud, so it is still there after you delete and reinstall the app, or on another device with the same Apple ID. Apple keeps it in your account; the developer cannot read it. To stop syncing: Settings › [your name] › iCloud, turn off Open Book in the list of apps using iCloud. Without iCloud the data stays on the device only.

3. Apple features used by the app

• Read-aloud runs on device: English uses the built-in iOS voices, Vietnamese uses the VieNeu-TTS voices that ship with the app. The text read aloud is not sent anywhere.
• Machine translation for passages without a translation uses Apple’s Translation framework, on device; iOS may download language files from Apple the first time.
• Dictionary uses the built-in iOS dictionary.
• If you chose to share analytics with app developers in iOS Settings, Apple may send anonymous crash reports. You can turn this off in Settings › Privacy & Security › Analytics & Improvements.

These features are provided by Apple and are covered by Apple’s privacy policy.

4. Children

The app collects no data from anyone, including children.

5. Your rights

Because the developer holds none of your learning data or identifying details, all of your learning data stays with you: you can view and edit it in the app, and delete it item by item in the app (deletions sync through iCloud too). Deleting the app removes only the copy on the device; the copy in your iCloud stays, so a reinstall brings it back. This policy is written to comply with Vietnam’s Personal Data Protection Law.

6. Changes

If the app ever changes how it handles data, this page will be updated first, with a new effective date.

7. Contact

For privacy questions, see the Support page.