In short: the documents you read and the notes you write stay on your device. DuoPage has no accounts and no ads, doesn’t use the advertising identifier and doesn’t track you across other companies’ apps or websites. To understand how the app is used, fix crashes, send optional notifications and manage DuoPage Pro, it collects a limited amount of anonymous technical data through Firebase (Google) and RevenueCat. We never sell this data or use it for advertising.
Your documents and notes
The documents you add (PDF, ePub, Word, text, Markdown, web pages and photos) are copied into the app’s private storage on your device and are never uploaded to us or anyone else. Your highlights, handwriting, page notes, notebooks, covers, reading progress and the questions you ask the study tools are stored the same way. Removing a book deletes its file and notes from the app; deleting the app removes everything it stored.
No analytics event, crash report or purchase record ever contains a book title, file name, the text of a document, your notes or your questions.
What we collect, and why
The data below is tied only to random identifiers generated on your device — never to your name, email address or Apple Account.
Usage statistics — Firebase Analytics (Google)
- Events from DuoPage: a book was added (file type only, such as “pdf”), a book was opened (file type and page count), the Pro screen was shown, Pro was purchased or restored, a study tool was used (which tool, and whether it ran on Apple Intelligence or an offline model), and an offline model was downloaded (which model).
- Collected automatically by Firebase: app opens, sessions and screen views; in-app purchase events (product, price and currency); device model, iOS version, app version, language, and an approximate country or region derived from a masked IP address; and a random app-instance ID.
- Why: to see which features are used and where the app needs improving.
Crash reports — Firebase Crashlytics (Google)
- When the app quits unexpectedly: the technical details of the crash (stack trace and app state), device model and iOS version. We also record certain handled errors — for example, a file that couldn’t be imported — with the type of error only.
- Why: to find and fix bugs.
Remote settings — Firebase Remote Config (Google)
- The app downloads a few settings we can change without an update, such as the number of books on the free shelf or the server offline models are downloaded from. Firebase receives the country, language, time zone and iOS version needed to deliver the right settings.
Notifications — Firebase Cloud Messaging (Google)
- So that we can announce new features, the app registers a push token together with device model, language, time zone and iOS and app version. Notifications are only shown if you allow them in Settings → Notifications inside DuoPage, and you can turn them off at any time in the iOS Settings app.
Purchases — RevenueCat
- DuoPage Pro is sold through the App Store and paid for through Apple. RevenueCat, our purchase service, keeps your purchase history (product, date, price and store transaction) under an anonymous user ID so that Pro can be verified and restored on your devices. It also receives your locale, currency and app version, and the Firebase app-instance ID so purchase events appear in our statistics.
- We never receive your name, Apple Account or payment details.
What we don’t do
- No accounts or sign-in.
- No advertising, no advertising identifier (IDFA) and no tracking across other companies’ apps or websites.
- No selling or sharing of data with data brokers or advertisers.
- No access to the contents of your books, notes or questions.
Other features that use the network
Offline AI models
If you choose to download an offline model (Settings → Offline AI), the app fetches the model file from Hugging Face or from our own download server. The request carries no information about you or your books — only what any download needs, such as your IP address. The model then runs entirely on your device.
Saving a web page
When you save a web page for offline reading, DuoPage downloads that page directly from the website you entered, like a browser would. That website’s own privacy policy applies to the request.
Features provided by Apple
Some features use system services built into iOS and are governed by Apple’s Privacy Policy:
- Apple Intelligence summaries, questions and flashcards run on your device.
- Face ID / Touch ID for locked books is handled by iOS; DuoPage never receives your biometric data.
- Look up, translation, text recognition and read aloud use Apple’s system frameworks.
- Widgets show your current book’s cover and progress using data shared only between DuoPage and its widget on your device.
Service providers
Firebase is provided by Google LLC and RevenueCat by RevenueCat, Inc.; both process data on our behalf, mainly in the United States. Their own policies apply: Privacy and Security in Firebase and RevenueCat Privacy Policy.
How long data is kept
- Usage statistics: up to 14 months.
- Crash reports: 90 days.
- Purchase records: for as long as needed to provide DuoPage Pro and to meet legal and accounting obligations.
Your choices
- Notifications: allow or block them in Settings → Notifications in DuoPage, or in the iOS Settings app.
- Start fresh: deleting the app removes your random identifiers; a new install gets new ones that can’t be linked to the old data.
- Access or deletion: email us and we’ll help where we can. Because the data isn’t tied to your name, please tell us roughly when you used the app and on which device.
Backups
App data may be included in your device’s iCloud or computer backups according to your settings. Those backups are managed by Apple, not by us. Downloaded offline AI models are excluded from backups.
Children
DuoPage is rated 4+. It doesn’t ask anyone for personal information, and the technical data described above is collected the same way for every user and never used for advertising.
Contacting support
If you email us, we use your address and message only to reply to you, and we don’t add you to any mailing list. You can ask us to delete our correspondence at any time.
Changes to this policy
If this policy changes, we’ll update this page and the date above. Significant changes will also be described in the app’s release notes.
Contact
Questions about privacy: support@halogroup.tech