Updated 30 October 2026

Privacy Policy

Book Duet is made by All Blue LLC. In short: the app has no account, no advertising and no third-party SDKs. To count installs and learn which of our links and ads work, it sends us a little pseudonymous usage data, tied to a random install ID. We never sell it, never share it and never use it to track you.

The app

• No account, no sign-in and no ads.
• No third-party SDKs and no tracking across other companies' apps or websites. The app never reads your device's advertising identifier and never asks for tracking permission.
• Every book, translation and word lesson is inside the app, so reading works offline. When your device is online, the app sends the usage data described below.
• Your reading position and settings stay on your device. The only settings we receive are your two languages.
• Listening uses the speech voices built into your device, so the text read aloud stays on your device.

What the app sends us

• A random install ID, made when you first open the app. Everything below is tied to this ID, which makes the data pseudonymous: it is never tied to your name, email address, or Apple or Google account.
• A few events and when they happened: opening the app, opening a book, seeing the unlock page, a purchase (which product, its price and currency) and restoring purchases.
• Technical details: the app version, your device model and type, the system version, your device's language and region settings, the country of your App Store or Google Play account, and the two languages you chose in the app.
• How you found the app, as your store reports it. On iPhone and iPad, Apple's attribution tells us whether the install came from an Apple Search Ads campaign, and Apple may send us privacy-preserving reports (SKAdNetwork) that confirm an ad led to an install without identifying you. On Android, Google Play's install referrer tells us which link or ad led to the install.
• Our app server does not store your IP address with this data; it uses it for at most a minute, to protect the service from abuse. Like any web server, our hosting's access logs may briefly record it for security.

How we use it

Only to understand and improve Book Duet: counting installs, seeing which links and ads bring readers, and learning which books and features are used. We do not sell this data, share it, use it for advertising or tracking, or combine it with data from other companies. We keep it for up to 24 months after the app was last used, then delete it or keep only aggregated counts.

Purchases

Book Duet is free to download. Its optional one-time purchases are handled by Apple (App Store) or Google (Google Play). We never receive your payment details: the app only tells us which product was bought and its price. Apple's and Google's own privacy policies cover the purchase.

This website

book-du-et.com uses no analytics, no advertising and no third-party services; its fonts and images are served from this site, and it sets no cookies for visitors. Like any web server, our hosting may briefly record technical request data such as IP addresses to keep the site running and secure. When you open one of our campaign links (book-du-et.com/go/…), we record the click (which link, the campaign named in it, the time, and whether it was opened on an iPhone, an Android device or a computer, but not your IP address) and send you on to the store.

Children

We do not knowingly collect personal information from children. The usage data described above is pseudonymous, is never sold and is never used for advertising or tracking.

Your choices

Deleting the app stops all collection, and a new install gets a new, unconnected ID. To have your data deleted, write to hello@book-du-et.com. The install ID is not shown anywhere, so tell us your device model and roughly when you installed the app; we delete what we can match.

Changes and contact

If this policy changes, the new version will appear on this page with a new date. Questions: hello@book-du-et.com.