Privacy Policy
This policy covers the Bookyeller app for Android and its sync service at sync.bookyeller.app. In this policy, "we" and "us" mean the maker of Bookyeller. The short version:
- Your audio files and books never leave your device, unless you turn on a cloud voice (see below).
- There are no accounts. We don't ask for your name, email or phone number.
- What sync sends is encrypted on your devices with a key only your devices have. We can't read it.
- No ads, no analytics, no tracking, and we don't sell or share your information.
- You can delete everything on the sync service from the app at any time.
On your device
Bookyeller reads the folder of books you choose, using Android's folder picker: audiobooks, and text books (.txt, .epub and .pdf files) that it reads aloud. It reads the files' names, tags, chapters, text and cover pictures to build your library, and keeps your listening places, earlier places, bookmarks and settings. All of this stays on your device unless you turn on sync.
The camera is used only to scan a pairing code when you add a device, and only if you allow it. The picture is read on the device and is never saved or sent anywhere.
If Android's own backup is on, your listening places, bookmarks and settings are included in your device's backup, which Google handles under your Google account settings. Bookyeller's sync key is always left out of that backup.
Sync
Sync is optional and off until you turn it on. When it's on, your devices send these to the sync service:
- where you are in each book (the file, the time, the playback speed, when you last listened, and whether you've finished it);
- your bookmarks, including any notes you write on them;
- for each book: its title, author, length, chapter names, and short fingerprints of its audio files, so your devices can recognize the same book;
- each device's name (you can change it), that it runs Android, and whether Sync was purchased on it.
All of this is encrypted on your device (AES-256-GCM) with a key that's created on your device and shared only by pairing your own devices. The key is never sent to us. We store only the encrypted data and can't read it.
To deliver and order the encrypted data, the service necessarily sees and stores some information that isn't encrypted: a random identifier for your group of devices, random-looking identifiers for each item, what kind of item each is (a place, a bookmark, a book or a device), its size, counters, and when it was received. It doesn't identify you.
Network information
The sync service doesn't record IP addresses. It uses your IP address for a moment, without storing it, to limit how often new groups can be created from one address. It runs on Cloudflare, which processes your IP address and basic connection details to deliver traffic and protect the service from attacks, as described in Cloudflare's privacy policy. Sync always uses an encrypted (HTTPS) connection.
How long data is kept
- On your device: until you delete it in the app or uninstall Bookyeller.
- On the sync service: until you delete it, or until 12 months after any of your devices last sent anything, whichever comes first.
- When an item is deleted, a marker without its contents is kept for up to 90 days so your other devices learn it's gone.
- The service's database keeps rolling backups for up to 30 days, so deleted data is fully gone from them within 30 days.
Deleting your data
- Everything on the sync service: in the app, open Settings and choose Delete my sync data (also on the Sync screen). This erases what all your devices have synced and turns sync off on all of them. Your books, places and bookmarks on each device stay.
- Just one device: on the Sync screen, choose Turn off sync on this device. Its places and device name are removed from the service.
- Everything on a device: uninstall Bookyeller, or clear its storage in Android's settings.
Because there are no accounts and we can't read what's stored, we can't find or delete your data for you without your key. If you've lost all your devices and your recovery code, your encrypted data is deleted automatically 12 months after it was last updated.
Adding books from a computer
When you open "Add books from a computer", your device accepts files from a browser on your own network while that screen is open, after the code it shows is entered. The files go straight from your computer to your device; nothing passes through us. Bookyeller only adds the files you send to your books folder, and never changes or removes your files there. The only files it removes are its own unfinished copies: when a file is sent again from the start, or a week after a transfer was given up.
Copying books between your devices
When your devices are paired, each one can see the titles of the books on your others (this is part of the encrypted information sync already shares). To copy a book, you open "Send to my devices" on the device that has it. While that screen is open, its address on your own network goes into its encrypted sync information, and your other devices fetch the book's files straight from it over your Wi-Fi. The files are encrypted with your devices' shared key on the way and never pass through us; we can't see the address or what is copied. Bookyeller only adds the copied files to your books folder, and never changes or removes your files there (only its own unfinished copies, as above).
Scanned books
Scanned PDFs are read by text recognition on your device; their pages are never sent anywhere. English is built in. If you download another language, your device fetches that language's file from bookyeller.app. We don't keep a record of who downloaded which language.
Cloud voices (only if you turn one on)
Text books are read aloud on your device by the voices installed on it. You can instead choose a cloud voice from OpenAI, ElevenLabs, Microsoft Azure or Google Cloud with your own account's key. Then, while you listen, the text of the book you're playing is sent from your device directly to that company, which makes the speech and charges your account. It never passes through us, and that company's privacy terms apply to it.
Your key is stored encrypted on that device only. It isn't backed up, synced to your other devices or sent to us. Speech already made is kept on the device for a while so it isn't paid for twice. Forgetting the key in Settings deletes both.
Purchases
Purchases are handled by Google Play. We don't receive your payment details or your Google account. The app checks with Google Play whether Sync was bought, and your devices share that as part of the encrypted device information above.
What we don't do
- No advertising, analytics, or tracking libraries, and no third-party sign-in.
- We don't sell or share personal information, and we don't use it for advertising.
- The app doesn't upload your audio files or your library to anyone. A book's text goes only to a cloud voice you chose yourself.
If you've chosen to share usage and diagnostics data with Google on your device, Google may give us anonymous crash and performance reports through Google Play. We use them only to fix problems.
Children
Bookyeller isn't directed at children under 13, and we don't knowingly collect personal information from them.
Changes
If this policy changes, we'll update it here and change the date at the top. If a change affects what the app sends, we will say so in the app.
Contact
Questions about privacy: hello@bookyeller.com.