Cal.com

Cal.com launched in 2021 as an explicit open-source alternative to Calendly, but it has grown into something broader: scheduling infrastructure that teams can host, embed, white-label, and extend rather than simply subscribe to. The core is AGPL-licensed TypeScript, deployable via Docker against a PostgreSQL database, and the repository is one of the most actively contributed scheduling codebases on GitHub with over 33,000 stars.

The feature set maps closely to Calendly's — booking pages, round-robin team scheduling, routing forms, reminder workflows, and deep integrations with Zoom, Google Meet, Outlook, Stripe, and HubSpot. Where it diverges is in what you can control. On self-hosted instances, white-label branding is unrestricted, per-seat pricing disappears entirely, and data stays on your own infrastructure. For scheduling-as-a-product use cases — a marketplace platform embedding booking for its vendors, or a SaaS tool adding appointment scheduling — that distinction is significant.

The managed cloud free tier is generous for individual use: unlimited one-on-one event types and the core integrations at no cost. Paid cloud plans layer on team features, routing, and priority support. The main self-hosting consideration is the footprint of the Next.js monorepo — it is a substantial application, and upgrades between versions require some care. For teams with the infrastructure appetite, the trade-off against per-seat perpetual licensing is usually straightforward.