Webhooks

In the dashboard → Settings → Webhooks → + New webhook:

• URL: your address, https:// only
• Events: one or more (see section 4)
• Secret: we generate it (whsec_…) and show it once — store it safely
• Number of attempts: 1 to 10, default 5

• Sending runs every minute — an event usually arrives within a minute.
• We wait 10 s for a response; success = HTTP 2xx.
• On any other response, timeout or network error we try again: 1st attempt immediately, then after 1 min, 5 min, 30 min and 2 h (with more than 5 attempts, each further one after 2 h).
• After the last attempt the delivery is marked “failed” — in the webhook detail you can send it again with the Resend button.
• Headers: X-Rezervacia-Event, X-Rezervacia-Delivery-Id, X-Rezervacia-Signature. Retries of the same delivery have the same X-Rezervacia-Delivery-Id — use it to process the event only once.

Every request contains the X-Rezervacia-Signature header in the format sha256=<hex>. Compute the HMAC from the raw request body (not from parsed JSON) and compare it in constant time (timing-safe).

Node.js (Express)

const crypto = require('crypto');

app.post('/webhook', express.raw({ type: 'application/json' }), (req, res) => {
  const signature = req.headers['x-rezervacia-signature']; // "sha256=<hex>"
  const secret = process.env.REZERVACIA_WEBHOOK_SECRET;

  const computed = 'sha256=' + crypto
    .createHmac('sha256', secret)
    .update(req.body) // raw body Buffer — NOT parsed JSON!
    .digest('hex');

  const a = Buffer.from(signature || ''), b = Buffer.from(computed);
  if (a.length !== b.length || !crypto.timingSafeEqual(a, b)) {
    return res.status(401).send('invalid signature');
  }

  const event = JSON.parse(req.body.toString());
  // A retried delivery has the same X-Rezervacia-Delivery-Id — process it only once.
  console.log('Event:', event.event, 'Delivery:', req.headers['x-rezervacia-delivery-id'], 'Data:', event.data);
  res.status(200).send('ok');
});

Python (Flask)

import hmac, hashlib, os
from flask import Flask, request, abort

app = Flask(__name__)
SECRET = os.environ['REZERVACIA_WEBHOOK_SECRET'].encode()

@app.post('/webhook')
def webhook():
    signature = request.headers.get('X-Rezervacia-Signature', '')
    body = request.get_data()  # raw bytes — do NOT parse JSON before verification!

    computed = 'sha256=' + hmac.new(SECRET, body, hashlib.sha256).hexdigest()
    if not hmac.compare_digest(signature, computed):
        abort(401)

    event = request.get_json()
    print('Event:', event['event'], 'Data:', event['data'])
    return 'ok', 200

PHP

<?php
$secret = getenv('REZERVACIA_WEBHOOK_SECRET');
$signature = $_SERVER['HTTP_X_REZERVACIA_SIGNATURE'] ?? '';
$body = file_get_contents('php://input'); // raw — NOT $_POST!

$computed = 'sha256=' . hash_hmac('sha256', $body, $secret);
if (!hash_equals($signature, $computed)) {
    http_response_code(401);
    exit('invalid signature');
}

$event = json_decode($body, true);
error_log('Event: ' . $event['event']);
http_response_code(200);
echo 'ok';

Ruby (Sinatra)

require 'sinatra'
require 'openssl'

SECRET = ENV.fetch('REZERVACIA_WEBHOOK_SECRET')

post '/webhook' do
  signature = request.env['HTTP_X_REZERVACIA_SIGNATURE'] || ''
  body = request.body.read

  computed = 'sha256=' + OpenSSL::HMAC.hexdigest('sha256', SECRET, body)
  halt 401 unless Rack::Utils.secure_compare(signature, computed)

  event = JSON.parse(body)
  puts "Event: #{event['event']}"
  status 200
  body 'ok'
end

⚠ NEVER verify the signature from parsed JSON. Libraries serialise JSON differently (whitespace, key order) — always use the raw request body.

• BOOKING_CREATED

  New booking — from the booking form, manual entry in the dashboard or via the API

  Fields in data: id, publicReference, confirmationCode, startAt, source (web / embed / manual)

• BOOKING_CANCELLED

  Cancellation — by the customer, by the business in the dashboard or via the API

  Fields in data: id; depending on the path publicReference, reason / cancellationReason, cancelledBy, refund, cancelledAt, via

• BOOKING_RESCHEDULED

  Rescheduling — by the customer, in the dashboard or via the API

  Fields in data: id; customer: oldStartAt, newStartAt · dashboard and API: previousStartAt, startAt, endAt, via

• BOOKING_COMPLETED

  The business marks the appointment as completed, or automatically after the appointment

  Fields in data: id, publicReference; for automatic and bulk changes completedAt / markedAt, via

• BOOKING_NO_SHOW

  The business marks the customer as a no-show

  Fields in data: id, publicReference

• CUSTOMER_CREATED

  A new customer’s first booking via the booking form

  Fields in data: customer { fullName, email, phone }, firstBookingId, source

• BOOKING_PAID

  Not sent yet — it can be selected, but Terminuj does not send this event today

  Fields in data: —

Every event has the same envelope: { event, occurredAt, tenantId, data }. The content of data differs by event and by where the change came from (section 4); it always contains the booking id (for CUSTOMER_CREATED, firstBookingId).

BOOKING_CREATED (booking form)

{
  "event": "BOOKING_CREATED",
  "occurredAt": "2026-06-10T10:30:00.000Z",
  "tenantId": "business uuid",
  "data": {
    "id": "booking uuid",
    "publicReference": "BK4F2H8K9M3N7P",
    "confirmationCode": "K7M2QX",
    "startAt": "2026-06-15T14:00:00.000Z",
    "source": "embed"
  }
}

BOOKING_CANCELLED (cancelled by the customer)

{
  "event": "BOOKING_CANCELLED",
  "occurredAt": "2026-06-12T08:15:00.000Z",
  "tenantId": "business uuid",
  "data": {
    "id": "booking uuid",
    "publicReference": "BK4F2H8K9M3N7P",
    "reason": "Illness",
    "cancelledBy": "customer",
    "refund": null
  }
}

In the list of webhooks, the Test button sends a test BOOKING_CREATED with a valid signature and "test": true in the envelope — a made-up booking, nothing is saved. Useful for checking before going live.