What is a webhook?
A webhook is an automated message that one system sends to another the moment a specific event happens. Something occurs in the first tool, and it immediately tells the second tool about it, with no scheduled sync in between.
Most integrations work the other way around. They rely on polling, where one system periodically asks another whether anything has changed, then pulls down updates. That builds in delay: a system that polls every hour can be working with data 59 minutes old. Webhooks flip the model and push data outbound right after the event, so a subscription, a purchase, or another flow-triggering action can reach a connected tool as it happens.
Why webhooks matter
Customers don't operate on batch schedules. A shopper who just abandoned their cart doesn't want to hear from you tomorrow, and a subscriber who just hit VIP status shouldn't wait until next week's sync to be recognized. When data moves on a timer, the response window closes before your systems catch up, and hours-old data means missed opportunities and disconnected experiences.
A few of the benefits of pushing data as it happens:
- Faster response: When an event fires soon after it happens, you can act while the customer is still in the moment.
- A connected stack: Every tool works from the same current data instead of its own stale copy.
- Less manual work: Processes that used to need scheduled exports and manual uploads run on their own.
Why choose Klaviyo for webhooks
Klaviyo is the autonomous B2C CRM, built on one real-time customer profile, so the data that travels with each webhook can carry real context, not just a bare event. And because you add webhooks as an action in the flow builder, a single customer action can trigger a message and a system update in the same flow.
Payloads that carry real customer context
Because Klaviyo webhooks fire from inside a flow, you construct the payload with data from the customer profile and the triggering event: profile properties, event properties, and custom fields. The receiving system learns who something happened to and why it matters, so it can take the right action.
Webhooks that fire from the same flow as your messages
You add a webhook as an action in the flow builder, right beside your email and SMS steps. One customer action can move through a flow that sends a confirmation email, a text, and a webhook to your loyalty platform, all from the same flow and the same data. A high-value purchase can post to your VIP tooling as the flow runs, instead of waiting for a nightly sync.
Automatic retries when a delivery fails
When a flow reaches a webhook step, Klaviyo sends an HTTP POST to your destination URL. If a delivery fails with a retry-able error, Klaviyo automatically retries with exponential backoff, and you can review send status in your webhook analytics to catch anything that didn't go through. You control which flow triggers fire a webhook, what each payload carries, and where it goes, so nothing sends without your setup.
Key features of webhooks in Klaviyo
Feature | Description | Available with Klaviyo |
|---|---|---|
Flow-builder webhooks | Add a webhook as an action at a specific step in a flow, alongside email and SMS | ✅ |
Context-rich payloads | Build the payload from profile properties, event properties, and custom fields | ✅ |
Retry on failure | Failed, retry-able deliveries are retried automatically with exponential backoff | ✅ |
Send-status analytics | Review whether each webhook posted successfully in your webhook analytics | ✅ |
Any connected system | POST to any tool with an application programming interface (API), plus pre-built App Marketplace connections | ✅ |
How to get started with Klaviyo
To start sending real-time data with Klaviyo webhooks:
- Identify the systems that need real-time data. List the tools that should react when a customer acts, like your loyalty program, fulfillment, or customer service tools.
- Build a flow around a triggering event. Webhooks fire from inside flows, so start from an event that can trigger a flow, like a subscription, a purchase, or a segment or list entry.
- Add a webhook action to your flow. In the flow builder, set the destination URL, headers, and the data the payload should carry.
- Customize the payload. Include the profile and event properties the receiving system needs to take the right action.
- Test and check delivery. Fire a test request, confirm the success response, and watch the connected system react. Building webhook payloads works best with developer resources on hand.
With real-time connections, the moment a customer acts is the moment your flow can tell the rest of your stack. Ready to move beyond batch syncs? Get started with Klaviyo today.