Cal.com
Open-source scheduling infrastructure — the self-hostable Calendly alternative.
About
Cal.com is the leading open-source scheduling platform: bookable event types, real-time availability across Google/Outlook/Apple calendars, round-robin and collective team scheduling, paid bookings via Stripe, and a full REST API (api.cal.com) plus webhooks — all of it self-hostable. With ~49,000 GitHub stars it is one of the most-starred open-source dev tools in existence, and the API surface is genuinely built for agents: create event types, query availability, and book meetings programmatically with OAuth2 or API keys.
One wrinkle worth knowing: the public repo was renamed to calcom/cal.diy — Cal.diy is the community-driven, 100% MIT fork with all commercial code removed, intended for self-hosters who want zero commercial dependencies. The hosted Cal.com product continues as the company's commercial offering. For most developers this is good news (a truly unencumbered fork exists), but check which codebase you're cloning.
Integrations cover Zoom, Google Meet, Teams, and dozens of calendar and payment providers, and the app-store model lets teams extend booking flows without forking. If scheduling is core to your product rather than a side feature, Cal.com is the rare tool that is both a polished SaaS and real infrastructure you can own.
What it can do
- API-first scheduling: event types, availability queries, booking create/cancel via REST
- Round-robin, collective, and managed team scheduling workflows
- Native Google Calendar, Outlook, Apple Calendar, Zoom, Meet, Teams integrations
- Paid bookings with Stripe; webhooks for booking lifecycle events
- App-store extensibility model; white-label booking pages
- Fully self-hostable MIT-licensed community edition (cal.diy)
Setup
- Use the hosted product at cal.com, or self-host:
git clone https://github.com/calcom/cal.diy.git. - Install dependencies (
yarn) and configure env (database, calendar OAuth credentials). - Run
yarn dxfor local development. - For API access, create an API key or OAuth app in settings.
Prerequisites
Node.js 18+ for self-hosting; a Postgres database. API use needs an API key or OAuth2 app; calendar integrations need Google/Outlook OAuth credentials.
Use cases
Works with
Trust score — 9/10
Scored 9/10 (verified tier, metrics-v1). Evidence: 49,017 GitHub stars (calcom/cal.diy, renamed from calcom/cal.com); pushed 2026-09-26; MIT license confirmed via GitHub API; One of the most-starred open-source dev tools; API-first scheduling verified against official docs; Repo renamed to cal.diy — the 100% MIT community fork with commercial code removed; hosted Cal.com continues as the commercial product. Manual review: scheduling infra claims (API, webhooks, 100+ integrations) verified; the cal.com/cal.diy split is recent — researchers should recheck which codebase they clone. License: MIT.
★ 49,017 GitHub stars
How the trust score is built
Full methodology →- Adoption · stars/downloads, log-scaled vs peers
- 9.0/10
- Maintenance · recency, releases, issue load
- 9.0/10
- Openness · license + docs
- 10.0/10
- Manual review · sanity read + red-flag check
- 8.0/10
- · 49,017 GitHub stars (calcom/cal.diy, renamed from calcom/cal.com); pushed 2026-09-26; MIT license confirmed via GitHub API
- · One of the most-starred open-source dev tools; API-first scheduling verified against official docs
- · Repo renamed to cal.diy — the 100% MIT community fork with commercial code removed; hosted Cal.com continues as the commercial product
- · manual review: scheduling infra claims (API, webhooks, 100+ integrations) verified; the cal.com/cal.diy split is recent — researchers should recheck which codebase they clone
Sources
Every fact above was checked against these sources. Where a claim comes from the provider and couldn't be independently verified, the text says so.