Privacy Policy for Shelfmark

Last updated: 2026-10-03

Shelfmark ("we", "our", or "the app") is a personal book-library app. This policy explains what information the app collects, how it is used, and the choices you have. Please read it carefully. If you do not agree, do not use the app.

1. Who we are

Shelfmark is operated by an independent developer.
Contact: [email protected].

2. Information we collect

We only collect information that is necessary to operate the app.

Account information. When you create an account, we collect your email address and an encrypted password via our authentication provider (Supabase). We do not see or store your password in plain text.

Library content you create. Books, libraries, tags, loans, and notes are stored on your device. You can use the app without an account; your library then stays only on your device. If you create an account, this content is also stored on our servers so it can be backed up and synced across your devices, and it is linked to your account. Cover photos you take or choose stay on your device and are not uploaded.

Camera and photo library access.

• The app uses your device camera to scan book barcodes and, optionally, to capture cover photos. Camera frames are processed on-device and are not transmitted to us. Only photos you explicitly save as covers are stored.
• The app uses your photo library only if you choose a photo as a book cover. We do not scan or read any other photos.

Analytics. We use PostHog to understand which features are used (for example, that a book was added or a lookup succeeded). These events are anonymous: they are not linked to your account, email address, or library content, and never include book titles or ISBNs. PostHog may derive an approximate location (country or region) from your IP address. Basic technical information such as app and OS version may also be processed by the OS platform and our providers for reliability. We do not use advertising SDKs.

Purchases. If you subscribe to Shelfmark Pro, Apple processes the payment. We use RevenueCat to verify your subscription status. RevenueCat receives purchase information (such as products and transaction dates) and an app-specific identifier, which is linked to your account if you are signed in. We never receive your payment details.

3. How we use information

We use the information above to:

• Authenticate you and keep you signed in.
• Sync and back up your library across your devices.
• Provide core features (scanning, metadata lookup, search).
• Diagnose crashes and bugs, and understand anonymously which features are used.
• Verify and restore Shelfmark Pro subscriptions.

We do not sell your personal data, and we do not use it for advertising or profiling.

4. Third-party services

• Supabase — hosts our database, handles authentication, and stores your library content. See supabase.com/privacy.
• Google Books API (Google LLC) — when you scan or search for a book, the ISBN or your search text is sent to Google Books to retrieve titles, authors, publishers, and cover thumbnails. Your account identifier is not sent. See policies.google.com/privacy.
• Open Library / Internet Archive — when you scan or search for a book, the ISBN or your search text is sent to Open Library to retrieve titles, authors, and covers. Your account identifier is not sent. See archive.org/about/terms.php.
• ISBNdb — when you scan or search for a book, the ISBN may be sent to ISBNdb to retrieve book details and covers. Your account identifier is not sent. See isbndb.com/privacy-policy.
• PostHog — anonymous product analytics, hosted in the EU. See posthog.com/privacy.
• RevenueCat — subscription status and purchase restoration. See revenuecat.com/privacy.
• Apple App Store / Google Play — distribute the app and handle crash reports.

These providers are independently responsible for the data they process.

5. Data retention and deletion

Your content is retained while your account exists. You can delete your account at any time from Settings → Delete account. Deletion is immediate and permanent: your authentication record, books, libraries, tags, and loans are removed from our servers and cannot be recovered. Library content that exists only on your device is removed when you delete the app. Anonymous analytics events are not linked to you and are retained by PostHog according to its retention settings.

6. Your rights

Depending on where you live (EEA, UK, California, and others), you may have the right to access, correct, export, or delete your personal data, and to object to or restrict processing. You can exercise most of these rights directly in the app. For anything else, email us at [email protected] and we will respond within 30 days.

7. Children

Shelfmark is not directed to children under 13 (or the equivalent minimum age in your jurisdiction). We do not knowingly collect personal data from children. If you believe a child has provided us data, contact us and we will delete it.

8. Security

We use industry-standard safeguards — encrypted transport (HTTPS), encrypted password storage, and access controls on our database. No system is perfectly secure; we cannot guarantee absolute security.

9. International transfers

Your data may be processed on servers located outside your country, including in the United States. By using the app you consent to such transfers.

10. Changes to this policy

We may update this policy from time to time. Material changes will be indicated by updating the "Last updated" date at the top of this page and, where appropriate, notified in the app.

11. Contact

Questions or requests: [email protected].