Create a Custom Klaviyo Event

What a custom event buys you

Klaviyo flows can start on metrics — not only native Shopify or form events. When you POST an event to the Events API, you create (or reuse) a metric by name and attach it to a profile. That metric can power a flow, split tests, and reporting like any other event. Common uses: back-office milestones (e.g. warranty registered), offline or partner actions, or anything Zapier can catch from another system — then pass those fields into Klaviyo as properties on the same event.

Name the metric and identify the person

metric.attributes.name is the human-readable metric name you will see in Klaviyo when building a flow (use a stable label such as EVENT NAME in the example below). profile.attributes.email (or phone with the right profile shape) ties the event to a person; Klaviyo merges on identifier. properties is a JSON object for anything else you want in the event — Zapier can map prior steps into key/value pairs here (order IDs, amounts, SKUs, pipeline stage, etc.). Start with {} and add fields as you need them.

In Klaviyo, open your account menu → Settings → API keys. Create a new private API key (not the public site key). Name it something you will recognize. Enable the scopes this integration needs — for the Events endpoint, include access to create events and read/write profiles as required by your account’s key model. Copy the key when it is shown; you typically cannot view the full secret again afterward. Store it only in secure places (password manager, server env vars) — never in frontend code or public repos. You will paste it into the curl command in the next step where it says YOUR_PRIVATE_API_KEY.

Replace YOUR_PRIVATE_API_KEY with your private key and person@yourdomain.com with the recipient. Replace EVENT NAME with the metric label you want to appear in Klaviyo. Authorization must use the prefix Klaviyo-API-Key . The revision header pins the API version — check Klaviyo’s docs if a newer revision is required. After a successful response, the metric appears under Metrics and can be selected as a flow trigger.

curl --request POST \
  --url https://a.klaviyo.com/api/events \
  --header 'Authorization: Klaviyo-API-Key YOUR_PRIVATE_API_KEY' \
  --header 'accept: application/json' \
  --header 'content-type: application/json' \
  --header 'revision: 2025-07-15' \
  --data '{
    "data": {
      "type": "event",
      "attributes": {
        "metric": {
          "data": {
            "type": "metric",
            "attributes": {
              "name": "EVENT NAME"
            }
          }
        },
        "profile": {
          "data": {
            "type": "profile",
            "attributes": {
              "email": "person@yourdomain.com"
            }
          }
        },
        "properties": {}
      }
    }
  }'

Use Zapier’s Webhooks by Zapier action (Custom Request): method POST, URL https://a.klaviyo.com/api/events, and the same headers as in the curl example. Build the JSON body from earlier Zap steps — map dynamic fields into properties and set the profile email from your trigger (e.g. CRM, spreadsheet, support tool). That way any Zap “flow” becomes a Klaviyo-visible event without a custom app. Other tools (Make, n8n, your own server) follow the same POST contract.

In Klaviyo: Flows → Create flow → trigger by metric → choose the metric name you used in the payload. Add filters on event properties if you only want certain property values to enter the flow. Send a test event from curl or Zapier, then verify the profile entered the flow in the flow’s activity view.