Cal.com Has a Free API: Open-Source Scheduling That Replaces Calendly

#opensource #productivity #webdev #tutorial

What is Cal.com?

Cal.com is an open-source scheduling platform — the Calendly alternative you can self-host. It handles booking pages, team scheduling, payments, and integrations with a full REST API.

Quick Start

git clone https://github.com/calcom/cal.com
cd cal.com
npm install
npx prisma migrate deploy
npm run dev

The REST API (v2)

export CAL_URL="https://api.cal.com/v2"
export CAL_KEY="your-api-key"

Event Types

# List event types
curl -s "$CAL_URL/event-types" \
  -H "Authorization: Bearer $CAL_KEY" | jq '.data[] | {title, slug, length}'

# Create event type
curl -X POST "$CAL_URL/event-types" \
  -H "Authorization: Bearer $CAL_KEY" \
  -d '{
    "title": "30 Min Meeting",
    "slug": "30min",
    "length": 30,
    "description": "Quick sync call"
  }'

Bookings

# List bookings
curl -s "$CAL_URL/bookings" \
  -H "Authorization: Bearer $CAL_KEY" | jq '.data[] | {title, start, status}'

# Create booking
curl -X POST "$CAL_URL/bookings" \
  -H "Authorization: Bearer $CAL_KEY" \
  -d '{
    "eventTypeId": 123,
    "start": "2026-04-01T10:00:00Z",
    "responses": {
      "name": "John Doe",
      "email": "john@example.com"
    }
  }'

# Cancel booking
curl -X DELETE "$CAL_URL/bookings/BOOKING_ID" \
  -H "Authorization: Bearer $CAL_KEY"

Availability

# Get available slots
curl -s "$CAL_URL/slots/available?eventTypeId=123&startTime=2026-04-01&endTime=2026-04-07" \
  -H "Authorization: Bearer $CAL_KEY"

# Set availability
curl -X POST "$CAL_URL/schedules" \
  -H "Authorization: Bearer $CAL_KEY" \
  -d '{
    "name": "Working Hours",
    "timeZone": "America/New_York",
    "availability": [
      {"days": [1,2,3,4,5], "startTime": "09:00", "endTime": "17:00"}
    ]
  }'

Webhooks

curl -X POST "$CAL_URL/webhooks" \
  -H "Authorization: Bearer $CAL_KEY" \
  -d '{
    "subscriberUrl": "https://myapp.com/webhooks/cal",
    "eventTriggers": ["BOOKING_CREATED", "BOOKING_CANCELLED"],
    "active": true
  }'

Embed in Your App

<!-- Inline embed -->
<cal-inline calLink="username/30min"></cal-inline>
<script src="https://app.cal.com/embed/embed.js"></script>

<!-- Or popup -->
<button data-cal-link="username/30min">Book a call</button>

Features

Booking pages: Customizable public pages
Team scheduling: Round-robin, collective, managed events
Payments: Stripe integration for paid bookings
Workflows: Automated emails/SMS reminders
Calendar sync: Google, Outlook, Apple Calendar
Embeds: Inline, popup, or floating button

Cal.com vs Calendly

Feature	Cal.com	Calendly
Open source	Yes	No
Self-host	Yes	No
Free events	Unlimited	1
Team scheduling	Free	$16/user/mo
API	Full REST	REST
Custom branding	Free	Paid
Payments	Stripe (free)	Stripe (paid plan)