Why Klaviyo Webhooks Matter

Want to automate more and do less?

Klaviyo webhooks give your brand the power to send and sync real-time data across platforms — without manual work or time delays. From triggering Slack alerts to updating your CRM or inventory system, webhooks are the secret weapon for advanced email and SMS automation.

But if you’ve only used Klaviyo for email flows, you might be missing out on its full potential.

In this guide, you’ll learn:

• What Klaviyo webhooks are and how they work

• When to use them (and when not to)

• Step-by-step setup instructions

• 6 powerful use cases that drive efficiency and ROI

• Testing tips, security best practices, and troubleshooting advice

Whether you're a CRM manager, marketing ops lead, or technically curious CMO — this guide will help you unlock smarter automation using Klaviyo webhooks.

What Are Klaviyo Webhooks?

A webhook is a way for Klaviyo to send real-time data to another system the moment an event occurs, like a purchase, list subscription, or custom action. Instead of pulling data manually, webhooks push data instantly to a specific URL (called an endpoint) using a POST request with a JSON payload.

Example: When someone places an order, Klaviyo can send that info to your shipping tool or Slack.

Types of Klaviyo Webhooks

Klaviyo offers two webhook types: Flow Webhooks for automation inside flows, and System Webhooks for platform-wide event tracking. Each suits different automation needs.

When to Use Klaviyo Webhooks

Ideal Use Cases

Klaviyo webhooks send real-time POST requests when flow-triggered events occur. They are ideal for automating external systems:

1. Notify Internal Systems When a VIP Customer Purchases

• Trigger: Placed Order with a custom profile property like LTV > £500

• Webhook Destination: CRM, Slack, or internal dashboard

• Purpose: Enable sales or CX teams to take immediate action

2. Sync Loyalty Points to Rewards Platforms (Smile.io, LoyaltyLion)

• Trigger: Placed Order

• Payload Includes: Email, order total, product SKU

• Benefit: Real-time point assignment and tier upgrades

• For full integration instructions, see our Smile.io x Klaviyo Integration guide, where we walk through how to set up automated point rewards that drive repeat purchases.

3. Trigger Slack Alerts for High-Value Leads Subscribing

• Trigger: Subscribed to List with filters based on email domain or interest tags

• Webhook Destination: Slack channel or lead management tool

• Benefit: Quick notification to SDRs or growth teams

• You can identify these VIP segments using the Klaviyo RFM Segments approach — a powerful way to tailor actions by customer behaviour and frequency.

4. Update Inventory in Real Time After an Order Is Placed

• Trigger: Placed Order

• Webhook Destination: ERP or warehouse software (e.g. ShipStation, NetSuite)

• Payload Includes: Line items, quantity, SKU, order ID

• Benefit: Prevents overselling and automates restocking workflows

5. Send Transactional Data to CDPs or Analytics Tools

• Trigger: Checkout, order, or custom metric events

• Destination: Segment, BigQuery, Snowflake, etc.

• Use Case: Attribution, funnel reporting, advanced lifecycle analytics

When Not to Use Webhooks

Webhooks are powerful, but they aren’t suitable for everything:

1. Subscribing Users to Lists

• Webhooks cannot add profiles to Klaviyo lists. Use the List Subscribe API instead.

2. Bulk Data Sync or Export

• For exporting profiles or large datasets, use the Profiles API or UI export options.

3. Email/SMS Engagement Events

• Engagement events like “email opened” or “link clicked” are not flow-triggered and can’t trigger webhooks.

How to Set Up a Webhook in Klaviyo

Flow Webhook Setup (Simple)

Klaviyo allows you to configure webhook actions directly within a flow, sending live data (such as post-purchase info) to external systems. Follow the steps below: 

1. Enable Two-Factor Authentication (2FA)
Only Admin, Manager, or Owner roles can add webhook actions once 2FA is enabled.

2. Create or Open a Flow
Start a flow with supported triggers (e.g., “Placed Order”, “Subscribed to List”) .

If you're just getting started with flows, our Klaviyo Flow Triggers 101 guide explains exactly which triggers are best for different use cases.

3. Add Webhook Block
Drag in the "Webhook" action where the event should trigger.

4. Configure Webhook

• Enter a valid HTTPS endpoint URL

• Add authentication headers (like Authorization: Bearer <token>)

• Use JSON payload with variables like {{ event.$event_id }} or {{ person.email }} .

5. Test & Save
Use Klaviyo’s preview mode or send test events to ensure correct payload and headers.

Important: Only supported flow triggers can fire webhooks. Unsupported triggers like “SMS Sent” or “Email Opened” won’t work.

System Webhook Setup (Advanced API)

For account-level events (e.g. "email_opened", "sms_sent"), you’ll need to use Klaviyo's Webhooks API.

1. Ensure API Access
Requires an advanced plan or partner account with webhooks:write OAuth scope .

2. Create Subscription
Send a POST request to /api/webhooks/ with:

3. List Available Events
Use /api/webhook-topics/ to fetch supported topics and confirm event compatibility .

4. Monitor & Retry
Use Klaviyo’s dashboard to test your webhook subscription, check delivery, and review error logs .

6 Practical Use Cases for Klaviyo Webhooks

Webhooks allow Klaviyo to send real-time data to external tools directly from flows. Here are 6 proven use cases:

1. Sync Orders to Shipping Platforms

Trigger: Placed Order
Action: Send order data (SKU, quantity, address) to tools like ShipStation or EasyPost
Why it works: Reduces fulfilment delays and improves delivery accuracy

2. Slack Alerts for VIP Customers

Trigger: Placed Order
Action: Notify sales teams via Slack when an LTV-tagged customer makes a purchase
Pro tip: Use a filter in the flow for customers with LTV > £500

3. CRM Profile Sync (HubSpot, Salesforce)

Trigger: Subscribed to List, Unsubscribed, or property update
Action: Push real-time profile data to your CRM to avoid misalignment across platforms

Want a full walkthrough of syncing your CRM? Read our HubSpot x Klaviyo Integration blog to learn how to link your pipelines and automate updates with ease.

4. Loyalty Platform Integration

Trigger: Placed Order
Action: Send purchase data to Smile.io or LoyaltyLion to auto-assign reward points

5. Multi-Step Logic via Zapier or Make

Trigger: Any flow event
Action: Use platforms like Zapier or Make to:

• Create a support ticket

• Send Twilio SMS

• Log data in Google Sheets

Zapier is also covered in our Klaviyo to Google Sheets post — showing you how to export and manage data for reporting or backup.

6. Trigger Internal Ops Based on Custom Events

Trigger: Custom metric (e.g. Demo Booked)
Action: Alert internal systems or start onboarding sequences
Why it works: Keeps operations in sync with user behaviour in real time

What Events Can Trigger a Klaviyo Webhook?

Klaviyo webhooks are currently only supported within Flows, and they function by sending HTTP POST requests to external systems when triggered by specific flow events.

Supported Flow Triggers

According to Klaviyo's guide, Flow Webhooks are limited to events that can be used as flow triggers, such as:

• List Triggered: When someone joins a list (e.g. newsletter subscribers).

• Segment Triggered: When someone is added to a specific segment (e.g. VIP customers).

• Metric Triggered: Based on custom or standard metrics like:

  • Started Checkout

  • Placed Order

  • Viewed Product

  • Ordered Product

  • Cancelled Order

  • Fulfilled Order

• Price Drop Trigger (when integrated with Klaviyo’s price drop tracking)

• Date-Based Trigger (e.g. birthday, renewal date)

For an overview of key flow metrics and how to use them to trigger smart automation, read our 8 Essential Klaviyo Flows to Boost Customer Loyalty.

What Can a Webhook Do?

Within a flow, the Webhook action lets you send a custom JSON payload to a destination URL. You can include:

• Profile properties (email, phone number, custom fields)

• Event details (order value, items, time)

• Conditional logic (e.g. only fire if order > £100)

Limitations

• Webhooks are only available within flows, not for campaign-level actions.

• System-wide events (like "Email Opened", "Clicked Link", or "Unsubscribed") cannot trigger webhooks directly.

• Use Klaviyo’s APIs or event subscriptions (via custom development) if you need real-time syncs based on non-flow activity.

Testing & Validating Your Webhook

Before activating any Klaviyo webhook, you should thoroughly test it to avoid misfired requests, broken automation, or incorrect data syncs.

Tools to Test Webhooks

You can test your webhook endpoints using these tools:

• Webhook.site
  Allows you to inspect real-time HTTP POST requests sent by Klaviyo. Use it to view the exact payload structure.

• Postman
  A robust API testing tool that lets you manually simulate POST requests using your webhook payload.

• Klaviyo Flow Analytics
  In the flow editor, click on the webhook step and check “Analytics” to confirm if the webhook was sent successfully and received a 200 OK response.

Need to audit more than just webhooks? Try our Klaviyo Custom Reports guide to set up automated reporting on webhook performance and more.

What to Validate

During testing, validate the following:

• Payload Accuracy
  Ensure fields like email, event_id, order_total, or any custom data are formatted correctly in your JSON.

• Authentication Headers
  If your endpoint requires a Bearer token or API key, add it in the Headers section of the webhook block.

• Response Status
  A 200 OK response confirms success. Errors like 401 (unauthorised) or 500 (server error) indicate a failed webhook.

• Retry Logic
  Klaviyo automatically retries failed webhook requests up to 5 times with exponential backoff, but it’s best to fix errors quickly to avoid issues.

Security Best Practices for Webhook Endpoints

To protect sensitive customer data and avoid misuse, Klaviyo requires secure webhook configurations. Here’s how to secure your endpoints properly:

1. Use HTTPS-Only Endpoints

All webhook URLs must use https:// to encrypt data during transmission. This prevents data from being intercepted or tampered with in transit.

2. Authenticate All Requests

For Flow Webhooks:

Use a Bearer token in the header to authenticate incoming requests.

Example Header:

Authorisation: Bearer YOUR_SECRET_TOKEN

For System Webhooks (via API):

Include a secret key when registering the webhook. You can then validate the request on your server using HMAC verification.

You can also explore how Klaviyo handles data securely in multi-platform setups via our Klaviyo x Salesforce Integration guide.

3. Whitelist Trusted IPs

If supported by your server or network setup, allow only specific IP addresses to access your webhook endpoints. This prevents unauthorised services from reaching your endpoint.

4. Validate the Payload

• Confirm all expected fields (e.g. event, profile.email, timestamp) exist before processing.

• Use schema validation to detect malformed or spoofed requests.

5. Monitor & Rate-Limit Webhook Traffic

• Log all requests for visibility and debugging

• Add rate-limiting logic to detect and stop abuse

These steps help enforce strong endpoint protection, data integrity, and request validation across your webhook integrations.

Common Errors and How to Fix Them

Even with a correct setup, Klaviyo webhooks can fail for various reasons. Below are the most common errors, their causes, and how to resolve them.

Error Table

Debugging Tips

• Test in a controlled flow: Create a simple flow with only a webhook step and trigger it manually. 

• Inspect response codes in Klaviyo Flow Analytics: Go to the flow → webhook step → View Details. 

• Use Webhook.site: Temporarily point your webhook to a webhook testing tool to view payloads and headers. 

FAQs

1. Can I use Klaviyo webhooks with Airtable or Google Sheets?

• Yes — trigger updates to Airtable rows or log events in Sheets using Zapier or Make.

2. How do I secure my Klaviyo webhook payloads?

• Use HTTPS endpoints and include an Authorization: Bearer <token> header. For advanced use, verify payloads with HMAC signatures if your server supports it.

3. What happens if the receiving server is down?

• Klaviyo retries failed webhook requests up to 5 times using exponential backoff. Always monitor responses via Flow Analytics and fix issues promptly.

4. Are webhooks supported in Klaviyo campaigns?

• No. Webhooks are only available in Flows, not for campaigns. Use APIs if you need to send data outside of flows.

5. Can I delay a webhook in Klaviyo?

• Yes. Use a “Time Delay” block before the Webhook action in your flow to control when the request is sent. You can learn more about conditional logic and timing in our Klaviyo Conditional Splits Guide.

Conclusion

Klaviyo webhooks are a powerful way to automate your marketing tech stack, syncing real-time data to CRMs, shipping tools, loyalty apps, and internal ops systems. Whether you're a growth marketer or technical lead, setting up secure and reliable webhooks can dramatically reduce manual work, improve response time, and deliver a seamless customer experience. With clear setup steps, supported triggers, and practical use cases, you’re now equipped to implement smarter automation that scales with your business.

Key Takeaways

• Webhooks enable real-time automation: Trigger external actions instantly when events occur in your Klaviyo flows.

• Two webhook types, and two different use cases: Flow Webhooks require no coding, while System Webhooks offer broader data subscriptions via API.

• Use cases span CRM syncs to inventory updates:  Automate loyalty points, notify teams, or update databases, without manual data pulls.

• Only specific triggers can fire webhooks: Metrics, segments, lists, and date triggers are supported, but email opens and unsubscribes are not.

• Testing tools are essential for debugging: Use Webhook.site, Postman, and Klaviyo Flow Analytics to confirm the correct setup and delivery.

• Security is non-negotiable: Always use HTTPS, authentication headers, and validate your payloads for data integrity.

Using Klaviyo webhooks but unsure if you’re doing it right?

We will examine your flows, triggers, and endpoint logic to guarantee you receive maximum value without any wasted requests. It’s free, quick, and customised for your business. Click here to request your free audit now.