How we protect your data.
Security features
End-to-end encryption
Your calendar content is encrypted on your device before it syncs anywhere.
- Authenticated encryption via libsodium secretbox
- Keys derived from your password on-device
- Servers store encrypted blobs plus limited sync metadata
- During normal sync, NimbleCal cannot read your event titles, notes, or descriptions in plaintext
Email invites are the main exception today. If you send an Email invite, NimbleCal stores and sends a plaintext invite summary with the event title, start/end time, timezone, organizer name/email, and any event location or description.
See: Encryption overview
Local-first architecture
Your data lives in your browser first (IndexedDB), so the app stays fast and offline-friendly.
- Local encrypted storage (RxDB / IndexedDB)
- Offline viewing and editing (syncs when you're back online)
- Import/export via ICS to avoid lock-in (note:
.icsfiles are plain text outside NimbleCal)
See: Offline mode
Privacy by design
Built from the ground up with privacy as the primary concern.
- No ads in the app
- No third-party analytics scripts in the app
- The website uses Plausible for cookie-free aggregate traffic and CTA measurement
- We do not sell your calendar content
Security practices
Defense-in-depth posture
We aim to keep the attack surface small and use reputable infrastructure providers for auth, hosting, and payments.
Responsible disclosure
There is a clear process for security researchers to report vulnerabilities responsibly.
Data-minimizing defaults
Most sensitive calendar content is encrypted end-to-end. Servers only see what is required to run accounts, billing, sync, reminders, and the invite details needed to send and show an email invite.
No calendar content recovery
Because calendar content is end-to-end encrypted, we cannot decrypt or recover it on your behalf. Quick unlock is a trusted-device local unlock helper, not recovery for a brand-new device. Password resets preserve access only when you can still unlock encryption on a trusted device; if you lose your password and every trusted-device unlock path, the fallback may be to start fresh.
Report a security issue
If you discover a security vulnerability, please report it responsibly to:
I appreciate your help in keeping NimbleCal secure for everyone.
Related: