calcom/cal.diy

Cal.com / "cal.diy" — the open-source Calendly alternative. Scheduling infrastructure that you can self-host or use as the hosted SaaS.

What it is

A TypeScript-based scheduling app: users connect a calendar (Google Calendar, Office 365, Apple Calendar), define availability rules + event types, and share booking links. Recipients pick a slot; the app creates the calendar event, sends invites, and handles reminders. T3-stack architecture (Next.js + tRPC + Prisma + Tailwind). Hosted at cal.com (recently rebranded as cal.diy in some surfaces) or self-hostable.

Key features

• Calendar connectors: Google, Office 365, Apple/iCloud, CalDAV, Zoom, Teams, Daily, Webex.
• Event types: 1:1, group, round-robin, collective, managed.
• Routing forms — direct bookings to the right team member based on form answers.
• Payments via Stripe / Razorpay for paid bookings.
• Embed widgets for any website.
• White-label / enterprise team features in the paid tier.
• MIT-licensed.

Tech stack

• TypeScript primary; T3 stack (Next.js + tRPC + Prisma + Zod + NextAuth + Tailwind).
• Turborepo monorepo.
• Postgres for data storage.

When to reach for it

• You want a Calendly alternative without the Calendly bill.
• You need branded scheduling infrastructure as part of your own app.
• You want self-hosted scheduling for compliance / data-residency reasons.

When not to reach for it

• You want zero-setup hosted scheduling — Calendly itself is faster to start.
• You want to avoid operating a Postgres + Next.js + Redis stack.

Maturity signal

45k stars, 14k forks, MIT, actively maintained. 4+ years under Cal.com Inc.

Alternatives

• Calendly — commercial, fully managed.
• SavvyCal — Calendly competitor with stronger team scheduling.
• Rallly — use for poll-style group scheduling.

Tags

typescript, nextjs, scheduling, calendar, self-hosted, t3-stack, prisma, mit-license, trpc