# Calendly Webhooks

## When to Use This Skill

* How do I receive Calendly webhooks?
* How do I verify Calendly webhook signatures?
* How do I handle `invitee.created` or `invitee.canceled` events?
* Why is my Calendly webhook signature verification failing?
* Setting up Calendly webhook handlers and debugging replay protection

## Verification (core)

Calendly signs each webhook with the `Calendly-Webhook-Signature` header, which
contains a timestamp and a signature: `t=<timestamp>,v1=<signature>`. Compute
`HMAC-SHA256` (hex) over `{timestamp}.{raw body}` using the subscription's
signing key, compare timing-safe, and reject stale timestamps (~3 min) to
prevent replay. Calendly has no SDK verification helper — verify manually and
always use the raw request body (don't `JSON.parse` first).

```javascript
const crypto = require('crypto');

function verifyCalendlySignature(rawBody, header, signingKey, toleranceSec = 180) {
  const parts = Object.fromEntries(header.split(',').map((p) => p.split('=')));
  const timestamp = parts.t;
  const signature = parts.v1;
  if (!timestamp || !signature) return false;

  // Reject stale timestamps to prevent replay attacks
  if (Math.abs(Math.floor(Date.now() / 1000) - Number(timestamp)) > toleranceSec) return false;

  const expected = crypto
    .createHmac('sha256', signingKey)
    .update(`${timestamp}.${rawBody}`) // signed content = timestamp + "." + raw body
    .digest('hex');

  try {
    return crypto.timingSafeEqual(Buffer.from(signature, 'hex'), Buffer.from(expected, 'hex'));
  } catch {
    return false; // length mismatch = invalid
  }
}

```

> For complete handlers with route wiring, event dispatch, and tests, see:
> 
> * [examples/express/](https://github.com/hookdeck/webhook-skills/tree/main/skills/calendly-webhooks/examples/express/)
> * [examples/nextjs/](https://github.com/hookdeck/webhook-skills/tree/main/skills/calendly-webhooks/examples/nextjs/)
> * [examples/fastapi/](https://github.com/hookdeck/webhook-skills/tree/main/skills/calendly-webhooks/examples/fastapi/)

## Common Event Types

| Event | Triggered When |
| --- | --- |
| `invitee.created` | An invitee schedules an event |
| `invitee.canceled` | An invitee cancels a scheduled event |
| `invitee_no_show.created` | An invitee is marked as a no-show |
| `invitee_no_show.deleted` | A no-show mark is removed from an invitee |
| `routing_form_submission.created` | A routing form is submitted |

> For the full event reference, see [references/overview.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/calendly-webhooks/references/overview.md) and [Calendly's webhook documentation](https://developer.calendly.com/api-docs/c1ddba8ce4a0d-webhook-subscriptions).

## Environment Variables

```bash
# Signing key returned when you create the webhook subscription
CALENDLY_WEBHOOK_SIGNING_KEY=your_webhook_signing_key_here

```

## Local Development

```bash
# Start tunnel (no account needed)
npx hookdeck-cli listen 3000 calendly --path /webhooks/calendly

```

## Reference Materials

* [references/overview.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/calendly-webhooks/references/overview.md) - What Calendly webhooks are, common events
* [references/setup.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/calendly-webhooks/references/setup.md) - Creating a webhook subscription, getting the signing key
* [references/verification.md](https://github.com/hookdeck/webhook-skills/blob/main/skills/calendly-webhooks/references/verification.md) - Signature verification details and gotchas