Cal.com vs OpenSlots
| Tagline | Scheduling infrastructure for everyone, the open-source Calendly alternative | Minimalist appointment slot booking system with email confirmation |
| Category | Scheduling & Booking | Scheduling & Booking |
| Replaces | Calendly, Acuity Scheduling | Calendly, Acuity Scheduling |
| GitHub stars | 46k | 400 |
| Language | TypeScript | PHP |
| License | AGPL-3.0 | MIT |
| Self-host difficulty | 3/5 Moderate | 2/5 Easy |
| Deploy options | One-Click Docker Docker Compose Manual | Manual Docker |
| Managed hosting | ||
| Last updated | 5 days ago | 7 months ago |
| View repo | View repo |
Where each falls short
The honest trade-offs — what you give up with each, versus the proprietary tools they replace.
Cal.com
- Some enterprise features (e.g. SAML SSO, advanced admin/insights, certain platform features) are gated behind a commercial/EE license even when self-hosting.
- Self-hosting requires PostgreSQL plus configuring numerous environment variables and OAuth credentials for calendar integrations.
- The core code is AGPL-3.0, which imposes copyleft obligations on modified network deployments.
- Upgrades between major versions occasionally require manual database migration work.
OpenSlots
- No recurring appointment or subscription booking support
- Email notifications only — no SMS or push
- No calendar sync (Google/Apple/Outlook)
Bottom line
Choose OpenSlots if you want the lower-effort setup; choose Cal.com for the larger community and ecosystem. Cal.com has seen more recent development. Open each guide below for deploy steps and the full feature gap.
Cal.com
Scheduling infrastructure for everyone, the open-source Calendly alternative