generated: '2026-07-24'
method: searched
source: https://guides.gitbook.io/integrationguide/gateway-functionality/features/receipts-and-notifications
type: Webhooks
note: >-
  Cardstream does not publish an AsyncAPI document and has no named event catalog.
  Asynchronous notification is handled via merchant-configured callback URLs (the
  "Receipts and Notifications" feature). This artifact captures the webhook/callback
  surface; there is no streaming or pub/sub event API to model as AsyncAPI.
spec_type: none
webhooks:
  transport: HTTP POST
  content_type: application/x-www-form-urlencoded
  payload: >-
    Same URL-encoded response fields as the synchronous transaction response
    (responseCode, responseMessage, transaction identifiers, etc.).
  signing: >-
    When message signing is enabled on the Merchant Account, data POSTed to any
    callback URL is signed (SHA-512 signature field), letting the merchant verify
    authenticity and integrity.
  channels:
    - name: callbackURL
      direction: gateway-to-merchant
      description: >-
        Server-to-server notification POSTed to the merchant's configured
        callbackURL, used to update backend systems independently of the browser
        redirectURL (recommended for Hosted Integration state updates).
    - name: redirectURL
      direction: gateway-to-browser
      description: >-
        The cardholder's browser is POSTed the signed transaction result to the
        merchant's redirectURL after a Hosted Payment Page completes.
  docs: https://guides.gitbook.io/integrationguide/gateway-functionality/features/receipts-and-notifications