n-The Klaviyo API, SDKs, and Webhooks: What They Actually Cover
Klaviyo's REST API covers profiles, events, Flows, campaigns, and segments, authenticated with a private API key generated in Account > Settings > API Keys. It's well documented and genuinely the foundation almost all custom Klaviyo integration work is built on, whether that's a custom storefront feed or a CRM sync a native connector doesn't reach.
What the API and SDKs actually let you build
The core of most custom integrations is the Events API: sending a custom event (a wholesale order, a loyalty point redemption, anything Klaviyo's native integrations don't already track) onto a profile, so Flows and segments can use it the same way they'd use a native Shopify event. Profile creation and updates work the same way, pushing custom properties onto a contact record.
Official SDKs exist for several languages, which cover the common request patterns (authentication, pagination, rate limiting) so most integration work doesn't start from raw HTTP calls. Klaviyo's developer documentation is detailed enough that most of what gets built doesn't need to wait on official support, the real blocker is almost always knowing which events and properties are worth sending, not the API itself.
Webhooks run the other direction: Klaviyo can call a URL you provide when specific events happen, letting another system react to Klaviyo activity (a Flow completing, a profile unsubscribing) in real time instead of polling the API on a schedule.
Where most of the real integration work actually happens
The hard part of a Klaviyo integration is rarely the API call itself, it's deciding which events matter and designing the profile properties so segments and Flows can actually use the data meaningfully. A wholesale order synced as a generic "purchase" event with no distinguishing property is far less useful than one tagged clearly enough to separate it from a retail sale in a segment.
This is the work underneath our broader Klaviyo integrations coverage →: the API is the mechanism, but the design of what gets sent and how it's structured is what actually makes a Flow or segment worth building on top of it.
What that looks like built out
Custom events designed to actually drive Flows
A wholesale order, a loyalty redemption, or a support resolution lands as a clearly structured Klaviyo event, tagged so a Flow or segment can distinguish it from a standard retail purchase.
Webhook-driven sync back to your other systems
A Flow completing or a profile unsubscribing in Klaviyo pushes that update to your CRM or support desk in real time, instead of someone checking Klaviyo manually.
What event or property is missing from your Klaviyo profiles?
Tell us what you're trying to track, and we'll design the integration around it, not just the API call.
Sending events to Klaviyo's API but not seeing them actually drive useful segments or Flows?
Tell us what you're tracking and what you're trying to trigger off it. The gap is usually in how the event or property is structured, not the API connection itself. The Klaviyo API is one example; n-frames builds whatever integration your business actually needs.
Let's talk