Cal.com
Scheduling infrastructure for everyone.
Founded in 2021 by Peer Richelsen and Bailey Pumfleet through Y Combinator, Cal.com was built as the open-source alternative to Calendly — a tool so universally hated for its UI and business practices that it inspired an entire community of developers to build something better. Cal.com is fully open-source, self-hostable, and built with a developer-first approach that allows teams to customize every aspect of the scheduling experience. The company raised $25 million in 2022 from Openview Ventures and prominent angels, and its open-source repository has over 30,000 GitHub stars, making it one of the most popular open-source projects in the developer tools space. Cal.com is used by individual professionals, developer teams, and enterprises including Vercel and Linear who need a flexible, privacy-respecting scheduling solution.
Active Founders
Peer Richelsen
Founder / CEO
Peer Richelsen is the co-founder and CEO of Cal.com. A German developer and serial open-source contributor, he built the original version of Cal.com as an open-source Calendly alternative out of frustration with the limited customization and privacy issues of existing scheduling tools. Peer's commitment to building in public and maintaining a fully open-source codebase has made Cal.com a beloved product in the developer community and a model for how open-source companies can build sustainable businesses.
Cal.com