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calrs

Fast, self-hostable scheduling. Like Cal.com, but written in Rust.

calrs is an open-source scheduling platform. Connect your CalDAV calendar (Nextcloud, Fastmail, BlueMind, iCloud, Google…), define bookable meeting types, and share a link. No Node.js, no PostgreSQL, no subscription.

Key features

  • CalDAV sync — pull events from any CalDAV server for free/busy computation, with multi-VEVENT support for recurring event modifications
  • CalDAV write-back — confirmed bookings are automatically pushed to your calendar
  • Availability engine — computes free slots from availability rules + calendar events
  • Recurring events — RRULE expansion (DAILY/WEEKLY/MONTHLY with INTERVAL, UNTIL, COUNT, BYDAY, EXDATE) blocks availability correctly
  • Event types — bookable meeting templates with duration, buffers, minimum notice
  • Booking flow — public slot picker, booking form, email confirmations with .ics invites
  • Email approve/decline — approve or decline pending bookings directly from the notification email
  • HTML emails — clean, responsive HTML notifications with plain text fallback
  • Groups — combined availability with round-robin assignment
  • Timezone support — guest timezone picker with browser auto-detection
  • Authentication — local accounts (Argon2) or OIDC/SSO (Keycloak, Authentik, etc.)
  • Web dashboard — manage event types, calendar sources, pending approvals, bookings
  • Admin panel — user management, auth settings, OIDC config, SMTP status, impersonation
  • Availability troubleshoot — visual timeline showing why slots are blocked
  • SQLite storage — single-file WAL-mode database, zero ops
  • Single binary — no runtime dependencies

calrs dashboard

How it works

  1. Connect your CalDAV calendar (or multiple calendars)
  2. Sync events so calrs knows when you’re busy
  3. Create event types with your availability schedule
  4. Share your booking link (/u/yourname/meeting-slug)
  5. Guests pick a slot, fill in their details, and book
  6. Both parties get an email with a calendar invite
  7. The booking appears on your CalDAV calendar automatically

License

AGPL-3.0 — free to use, modify, and self-host.