NimbleCal
Last reviewed Jan 22, 2026

NimbleCal is a modern web app. If you're using a recent version of Safari, Firefox, or a Chromium-based browser (Chrome, Edge, Brave, etc.), you're in a good place.

What NimbleCal needs from your browser

NimbleCal depends on a few browser capabilities:

  • Browser storage (IndexedDB + local/session storage) for local-first data (fast + works offline).
  • WebAssembly (WASM) for end-to-end encryption (libsodium).
  • Web Crypto API for secure key handling (requires HTTPS or localhost).
  • Cookies (first-party) for sign-in.
  • Notifications (optional) for reminders.

If any of these are disabled by your browser (or an extension), NimbleCal can feel "broken" even though nothing is wrong with your account.

NimbleCal does not rely on third-party cookies, but it does need first-party cookies on the app domain to keep you signed in.

Any modern desktop browser works well. This includes privacy-focused browsers like Brave, Mullvad Browser, LibreWolf, etc.

Mobile web limitations

Mobile browsers have platform limitations
NimbleCal works best on desktop. Mobile browsers (iOS Safari, Android Chrome) can be used for basic viewing, but key features like reminders and background sync don't work reliably due to platform restrictions. iOS and Android apps are in development.

What doesn't work well on mobile web:

  • Reminders — Mobile browsers can't wake up the app in the background to show notifications
  • Background sync — Events won't sync unless the app is open
  • Storage persistence — iOS may clear your data after 7 days of non-use

For the full experience, use NimbleCal on a desktop browser.

Private browsing and aggressive blocking

Private browsing modes and some privacy/enterprise settings can block storage or cookies.

Privacy-focused browsers are welcome. If your browser clears site data on close or blocks all cookies/storage by default, you may need to allow site data for NimbleCal to stay signed in and save offline data.

If you're stuck on a loading screen (or your data won't save), try:

  1. Open a normal (non-private) window.
  2. Temporarily disable ad/script blockers for app.nimblecal.com.
  3. Reload.

Reminders and notifications

Reminders rely on browser notifications. If reminders are not showing:

Installing NimbleCal gives you a dedicated icon and a standalone window.

See: Install NimbleCal (app)