Kubun Notes ("the app") is developed by Kubun Labs. We believe your reading list, personal quotes, and private notes belong exclusively to you. Everything you capture remains stored locally on your device and backed up securely to your personal Google Drive.
Kubun Notes requires Google Sign-In to use the app. When you sign in, we collect:
This information is stored locally on your device and is never transmitted to Kubun Labs servers. The app also remembers which Google account your library was last backed up to, even after you sign out, so that signing in with a different account never overwrites that account's backup without asking you first.
Google Drive Backup: Your library (books, notes, highlights, chapters and topics, reading status, ratings, and cover photos) is automatically backed up to a hidden app-specific folder in your Google Drive using the drive.appdata scope. This folder is:
Backups remain in your personal Google Drive storage and are never accessible to Kubun Labs.
Your books, notes, reading status (Reading, Read, Want to Read), personal star ratings (1–5 stars), highlighted passages, and the chapters and topics you assign to notes are stored in a private database on your device. They are never uploaded to Kubun Labs or any unauthorized third party.
If you photograph a physical book cover, that image is stored in app-private local storage (filesDir/covers/). You can also generate local backups as JSON files exported directly to your device's Downloads/BookNotes/ directory for manual transfer or archiving. These files are plain text, so anyone with access to your device's files (for example through a computer connected by USB) can read them.
Android's own device backup, if you have it turned on, may also include the app's database and settings in the encrypted backup Google keeps for your device. Downloaded speech models are excluded from it.
Camera access is requested for three specific user actions:
Microphone access is requested exclusively to transcribe spoken notes using an embedded, 100% offline speech-to-text engine powered by whisper.cpp. Audio recording is processed locally on your device's CPU/GPU and discarded immediately after transcription. Audio data is never uploaded, streamed, or transmitted to any cloud server.
If you choose to download additional Whisper transcription models (e.g. Fast, Balanced, or Most Accurate), model weights are fetched directly from the public open-source release on Hugging Face and checked against a fixed fingerprint before use. Like any download, the request is visible to Hugging Face; Kubun Notes adds no tracking or telemetry to it.
When searching for books by title, author, or ISBN barcode, search queries route through an edge API orchestrator operated by Kubun Labs, which queries Open Library and Google Books catalogues. Only the search terms or ISBN digits you typed/scanned are transmitted to execute the search.
Searches that find no book at all are recorded, without any identifier attached, so we can see which books the catalogues are missing. Book cover images are loaded directly from Open Library and Google Books, which see the request like any website you visit.
Kubun Notes offers an opt-in AI recommendation feature ("What to read next"). This feature fires only when explicitly requested by tapping "What to read next" in your library.
When requested, the app transmits only book titles, authors, personal star ratings, reading status, and preferred filters (language, era, kind of book) to our Cloudflare edge proxy, which forwards to a commercial AI inference provider. YOUR NOTES ARE NEVER SENT. Neither is any identifier: no device ID, advertising ID, account email, or name. Like any server, our edge service sees the network address your request comes from; it is used only to limit how often requests can be made, is not stored with your request, and is never passed to the AI provider.
We use only AI providers with zero data retention policies, meaning your book data is never stored or used for AI model training.
If you hand-create a custom book that does not exist in public catalogues, Kubun Notes may offer an option to contribute the metadata (title, author, ISBN, year, page count, and cover photo) to a shared community catalogue. This is 100% optional, write-only, and explicitly prompted per book. Your notes are never included.
You have complete control over your data:
Downloads/BookNotes/ stay until you delete them.If you have any questions or feedback regarding this Privacy Policy, please contact Kubun Labs at: andrespra@gmail.com.