Privacy Policy

Last updated: 18 April 2026

LeitnerBox is a local-first flashcard app. The core product runs entirely on your device and never contacts our servers. This policy explains what happens in the narrow cases where data does leave your device, and what we do (and don't do) with it.

1. Data we collect

If you never sign in: we collect nothing. Your cards, progress, and preferences live only in your browser's IndexedDB or the iOS app sandbox.

If you enable cloud sync or sign in with Apple / Google / email: we store the minimum required to let you log back in and sync:

• An opaque user ID from your identity provider (Apple sub, Google sub, or a hash of your email)
• Your email address, if you provide it
• The card content you explicitly chose to sync
• Session tokens bound to the devices you authenticated on
• Basic request metadata (IP address, user-agent) retained for 30 days for abuse prevention

2. Data we do not collect

• Behavioural analytics or event tracking
• Advertising identifiers (IDFA, GAID)
• Location data
• Contact lists, photos, or device sensors beyond what you pick in-app
• Data about what you're studying, when you study, or how you answer (unless you enable Pro analytics, which stays on our servers only)

3. Where data is stored

Cloud sync data is stored on Cloudflare (Workers + D1 + R2) in their EU and US regions. Cloudflare acts as our data processor. We don't use any other third-party services for user data.

4. Who we share data with

Nobody. We don't sell, rent, or share your data with advertisers, analytics providers, or data brokers. Law enforcement requests would require a valid legal order; we'd push back on anything overbroad and notify you if legally possible.

5. Your rights

• Export: every LeitnerBox version has a one-tap CSV export of all your cards.
• Delete: Settings → Account → Delete Account wipes every trace within 7 days (backup retention).
• Access: email [email protected] with your account email and we'll send everything we store about you within 14 days.
• Correct: edit anything in-app; cloud sync overwrites server-side.

6. Children

LeitnerBox is rated 4+ on the App Store but we don't knowingly collect data from anyone under 13. If you're a parent and believe we have, email us and we'll delete it.

7. Changes

If we change what we collect, we'll update the "last updated" date above and notify signed-in users by email at least 30 days before the change takes effect. Material changes to paid features respect the Free Sync Promise on our home page.

8. Contact

Questions, requests, or complaints: [email protected]. We read every email.