Cal.com

Cal.com is the open source scheduling tool that actually matches Calendly feature-for-feature, which is rare in the open source world. The self-hosted version removes all premium restrictions — you get multiple calendars, event types, team scheduling, round-robin assignment, and integrations with Zoom, Google Meet, and Teams without paying a dime. The interface is polished and the booking flow is smooth for both hosts and guests. What makes Cal.com special is how it handles the full scheduling lifecycle: availability management, timezone handling, conflict detection, and automated reminders all work seamlessly. The API is well-documented, making it easy to integrate with other tools. The trade-off is the setup complexity: self-hosting requires a database, caching layer, and email service configuration. It's not a five-minute install. But if you're tired of Calendly's per-user pricing or need features locked behind their enterprise plan, Cal.com gives you everything for free.

Best for users who are comfortable following setup instructions or running a self-hosted tool.