Privacy Policy
Northern Field Studio ("we", "us", or "our") built the Mighty Bookshelf app. This page informs you of our policies regarding the collection, use, and disclosure of personal information when you use our app.
1. Information We Collect
Mighty Bookshelf is designed to work primarily on your device. Most of what the app does — storing your library, tracking reading status, browsing your collection — never leaves your phone.
- Book data you enter: titles, authors, reading status, etc. are stored locally on your device. We do not have access to this data.
- ISBN lookups: when you search for a book by ISBN, your request is forwarded to the Google Books API to retrieve metadata. Your IP address is visible to our server during this request and is used solely for rate-limiting purposes; it is not logged or stored. The search query and its result may be cached on our server for up to 30 days to speed up repeat lookups and reduce load on Google's API — this cache is keyed by the query itself, not by you or your device, and is not linked to your identity.
- Book search: when you make a broad search from within the app, your request is forwarded to the Google Books API the same way, with the same rate-limiting and caching behavior described above for ISBN lookups.
- Cover and creative web search: when you search for a book cover or look up an author, illustrator, colourist, or letterer, the app opens your device's own browser (Chrome Custom Tabs on Android, Safari on iOS) to run that search directly with Google or your default search provider. This traffic goes straight from your device to the search provider — it never passes through our servers, and we have no visibility into it.
- Search history: the terms you've searched in-app are saved locally on your device so you can quickly reuse them. This history is never sent to us. You can delete individual entries or clear all of it at any time from the app's Settings screen.
- In-app purchases: when you buy additional book slots, your device sends us a device identifier (a random identifier generated by your operating system — not your name, email, or Google/Apple account), together with the product purchased, a purchase token, and an order ID, so we can verify your purchase and keep track of how many slots you've unlocked. We keep this record for as long as needed to honor your purchase entitlement.
- Crash reports and basic usage analytics: we use PostHog, hosted in the EU, to understand app stability and usage. This includes crash and error reports, and basic events such as app opens, screen navigation, and deep link opens, along with standard technical context (device model, OS version, app version). This does not include your book data, search history, or any content you've entered in the app. We do not use session replay, advertising identifiers, or any advertising/tracking SDKs.
- No account required: we do not collect names, email addresses, or any account credentials.
2. Third-Party Services
We use the Google Books API to retrieve book metadata when you perform an ISBN lookup or a broad search. Requests to this service are subject to Google's Privacy Policy. No personally identifiable information is included in these requests.
Cover and creative web searches are handled entirely by your device's own browser and your default search provider (typically Google), subject to their own privacy policies — we are not a party to that traffic at all.
In-app purchases are processed by Google Play Billing or Apple's In-App Purchase system, depending on your platform, and are subject to Google's or Apple's respective privacy policies. We only receive the purchase confirmation details described above — never your payment information.
We use PostHog (EU-hosted) for crash reporting and basic usage analytics, as described in Section 1. Requests to this service are subject to PostHog's Privacy Policy.
3. Data Storage and Security
Your library data lives on your device. If you use iCloud sync (iOS/macOS), your data is stored in your personal iCloud account and governed by Apple's Privacy Policy. We do not operate our own cloud database for user library data.
Our API server persists two things: your purchase records (so we can honor book-slot entitlements you've paid for), and a short-lived cache of search/ISBN results (up to 30 days, not linked to your identity) to reduce load on Google's API. It does not persist your book library, search history, or IP address. All communication between the app and our server is encrypted in transit using TLS.
4. Analytics and Tracking
We use PostHog for crash reporting and basic usage analytics — see Section 1 for what that includes. We do not use advertising identifiers, session replay, or any advertising/tracking SDKs, and we do not share any data with advertising networks or data brokers.
5. Children's Privacy
Mighty Bookshelf is not directed at children under the age of 13. We do not collect or sync personal information from children or anyone else. If you believe your child has entered personal information in the app, you can remove it yourself locally.
6. Changes to This Policy
We may update this Privacy Policy from time to time. Changes will be posted on this page with an updated "Last updated" date. We encourage you to review this page periodically.
7. Contact Us
If you have any questions about this Privacy Policy, please contact us at: contact@northernfieldstudio.app