Cal.com is open-source scheduling: booking pages, team round-robins, routing forms and workflows, all self-hostable and deeply customizable. The free individual plan covers real client booking — including integrations and unlimited event types — without the upsell wall competitors put exactly there.
It suits developers and teams who want scheduling under their own control, whether that means white-labeling, self-hosting for compliance, or building on the API. If you just need a personal booking link with zero setup, Calendly remains the more polished default.