generated: '2026-07-28'
method: searched
source: >-
  https://docs.viator.com/partner-api/technical/ (Bookings section, BookingEvent schema) and
  https://docs.viator.com/supplier-api/technical/ (What's new - Notification Webhooks, Connectivity
  overview, Viator APIs tag), plus openapi/viator-partner-api-v2-openapi.json and
  openapi/viator-reservation-system-api-openapi.json
spec_type: none
asyncapi_published: false
asyncapi_probe:
  urls_checked:
  - https://api.viator.com/asyncapi.json
  - https://docs.viator.com/asyncapi.yaml
  finding: >-
    No AsyncAPI document is published on any Viator surface, and the docs host answers 403
    AccessDenied for any object it does not hold. Viator's event surface is real but is described
    entirely in OpenAPI and prose. Nothing was fabricated to fill this gap.
summary: >-
  Viator has three distinct event surfaces and none of them is a classic outbound HTTP webhook to a
  partner-supplied URL. On the demand side, booking events are delivered by a cursored PULL feed
  with a server-side acknowledgement cursor. On the supply side, Viator hosts inbound notification
  endpoints that a reservation system POSTs to when availability, capacity, pricing or special
  offers change - Viator's own documentation calls these "Notification Webhooks". Also on the supply
  side, the entire Reservation System API is an inverted callback contract: the operator's booking
  software implements the endpoints and Viator calls them.

surfaces:

- name: Booking event feed (demand side)
  direction: partner pulls from Viator
  transport: https
  pattern: cursored delta feed with explicit acknowledgement
  spec: openapi/viator-partner-api-v2-openapi.json
  operations:
  - operationId: bookingsModifiedSince
    method: GET
    path: /bookings/modified-since
    description: >-
      Returns booking events modified since a timestamp or cursor. Events initiated by the partner
      through the API are excluded by default - this is a feed of things that happened TO the
      partner's bookings, not an echo of its own writes.
  - operationId: bookingsModifiedSinceAcknowledge
    method: POST
    path: /bookings/modified-since/acknowledge
    description: >-
      Acknowledges a list of transactionRefs. For supplier-initiated cancellations, acknowledging
      before the event's acknowledgeBy timestamp transfers ownership of the customer-communication
      obligation to the merchant partner.
  message:
    name: BookingEvent
    schema: openapi/viator-partner-api-v2-openapi.json#/components/schemas/BookingEvent
    required: [transactionRef, eventType, acknowledgeBy, bookingRef, partnerBookingRef, lastUpdated,
      bookedItem]
    id_field: transactionRef
    id_format: PBE-<uuid>
    correlation_fields: [bookingRef, partnerBookingRef]
  event_types:
  - type: CONFIRMATION
    description: The booking was confirmed.
    acknowledgement_required: false
  - type: REJECTION
    description: The booking was rejected by the supplier.
    acknowledgement_required: false
  - type: AMENDMENT
    description: >-
      The booking was amended. Amendments actioned through the amendment endpoints are not returned.
    acknowledgement_required: false
  - type: CANCELLATION
    description: The booking was cancelled by the supplier.
    acknowledgement_required: true
    note: >-
      The only event type with an acknowledgeBy deadline; refundPercentage is always 100 because the
      supplier cancelled.
  - type: CUSTOMER_CANCELLATION
    description: >-
      The booking was cancelled by the customer. Cancellations actioned through bookingsCancel are
      not returned.
    acknowledgement_required: false
    added: '2024-07-29'
  access: >-
    Opened to all partner types on 2025-09-11; the acknowledge endpoint remains restricted to
    Full-access + Booking affiliates and merchant partners.

- name: Viator-hosted notification endpoints (supply side)
  direction: reservation system pushes to Viator
  transport: https
  pattern: inbound notification webhook hosted by Viator
  spec: openapi/viator-reservation-system-api-openapi.json
  status: beta
  viator_terminology: Notification Webhooks
  operations:
  - operationId: eventNotification
    method: POST
    path: /v2/notification/events
    description: >-
      Lets a reservation system notify Viator when pricing changes, or when capacity and
      availability change, so Viator can prevent overbookings and surface last-minute inventory.
    signals: [salability, capacity, pricing]
    sla: {p90_seconds: 1, acceptable_seconds: 2, max_monthly_error_rate: 0.5%}
  - operationId: specialOffersNotification
    method: POST
    path: /v2/notification/special-offers
    description: >-
      Notifies Viator of new or updated special offers so discounted inventory is merchandised
      correctly.
    sla: {p90_seconds: 1, acceptable_seconds: 2, max_monthly_error_rate: 0.5%}
  supersedes:
  - operationId: availabilityNotification2
    path: /availabilitynotification2
    status: deprecated

- name: Inverted callback contract (supply side)
  direction: Viator calls the reservation system
  transport: https
  pattern: >-
    The Reservation System API specification defines endpoints the operator's booking software must
    itself implement and expose for Viator to call. Functionally these are webhooks with Viator as
    the sender and a published contract, SLA and circuit breaker attached.
  spec: openapi/viator-reservation-system-api-openapi.json
  server_placeholder: https://your-reservation-system.example.com
  authentication: {scheme: apiKey, in: header, name: X-Api-Key}
  callbacks:
  - {operationId: tourList, path: /tourlist, mandatory: false, purpose: inventory mapping}
  - {operationId: availabilityCheck, path: /v2/availability/check, mandatory: true, purpose: real-time
      capacity check}
  - {operationId: calendar, path: /v2/availability/calendar, mandatory: true, purpose: long-term
      availability, pricing and offers}
  - {operationId: specialOffers, path: /v2/product/special-offers, mandatory: false, purpose: special
      offer metadata}
  - {operationId: reserve, path: /v2/reserve, mandatory: true, purpose: hold inventory and price
      during checkout}
  - {operationId: booking, path: /booking, mandatory: true, purpose: create the booking after payment}
  - {operationId: bookingAmendment, path: /booking-amendment, mandatory: false, purpose: apply
      post-confirmation changes}
  - {operationId: bookingCancellation, path: /booking-cancellation, mandatory: true, purpose: cancel
      and free inventory}
  - {operationId: redemption, path: /redemption, mandatory: true, purpose: redemption status at
      cancellation time}
  failure_handling: >-
    Failed API bookings, amendments and cancellations fall back to email notification of the
    operator. Successful API calls generate no operator email. A persistently degraded reservation
    system has its circuit breaker opened by Viator at a 70% failure rate.
  sla: lifecycle/viator-lifecycle.yml

outbound_webhooks_to_partner_urls: false
outbound_webhooks_note: >-
  Viator does not let a demand-side partner register a callback URL. Booking events must be polled
  from bookingsModifiedSince. Recorded as measured absence.