Klaviyo Webhooks

When to Use This Skill

• How do I receive Klaviyo webhooks?
• How do I verify Klaviyo webhook signatures (the Klaviyo-Signature header)?
• How do I handle Klaviyo system webhook events like event:klaviyo.opened_email?
• Why is my Klaviyo webhook signature verification failing?
• How do I secure a Klaviyo flow "Webhook" action that isn't signed?

Verification (core)

Klaviyo signs each system webhook with an HMAC-SHA256 over the raw request body concatenated with the Klaviyo-Timestamp header value, hex-encoded, using your endpoint secret (min 16 chars). The signature arrives in the Klaviyo-Signature header. Compute the same HMAC and compare timing-safe. There is no official SDK verification helper, so verify manually. Pass the raw body — don't JSON.parse first.