Webhooks overview

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Core concepts

• Endpoint — a URL you register to receive deliveries, plus the set of events it listens to. Create and manage endpoints through the V4 API (/v4/webhook_endpoints) or in Kit at app.kit.com/webhooks.
• Subscription — the link between an endpoint and an event type. One endpoint can subscribe to many events.
• Event — something that happened in the account (for example subscriber.created). Every event has a UUID id you can use to deduplicate.
• Delivery — one POST to one endpoint, carrying an array of 1 to 100 events of the same type. Most deliveries carry a single event; bulk activity batches into fewer, larger deliveries.

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What a delivery looks like

{
  "delivery_id": 123456,
  "events": [
    {
      "id": "9c2e1f3a-6b7d-4e8f-a1b2-c3d4e5f60718",
      "type": "subscriber.created",
      "created": "2026-07-29T14:32:10Z",
      "data": {
        "subscriber": {
          "id": 987654,
          "first_name": "Ada",
          "email_address": "ada@example.com",
          "state": "active",
          "created_at": "2026-07-29T14:32:10Z",
          "fields": {}
        }
      }
    }
  ]
}

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Webhook endpoints supersede the legacy webhooks API

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Next steps