Customer.io Hello World

Overview

Create a minimal working Customer.io integration: identify a user (create/update their profile), track an event, and send a transactional email. This covers the three fundamental Customer.io operations.

Prerequisites

• customerio-node

  installed (

  npm install customerio-node

  )

• CUSTOMERIO_SITE_ID

  and

  CUSTOMERIO_TRACK_API_KEY

  configured

• CUSTOMERIO_APP_API_KEY

  configured (for transactional email example)

Instructions

Step 1: Identify a User (Create/Update Profile)

// hello-customerio.ts
import { TrackClient, RegionUS } from "customerio-node";

const cio = new TrackClient(
  process.env.CUSTOMERIO_SITE_ID!,
  process.env.CUSTOMERIO_TRACK_API_KEY!,
  { region: RegionUS }
);

// identify() creates the user if they don't exist, or updates if they do.
// The first argument is your internal user ID (immutable — use DB primary key).
await cio.identify("user-123", {
  email: "hello@example.com",          // Required for email campaigns
  first_name: "Jane",
  last_name: "Doe",
  plan: "pro",
  created_at: Math.floor(Date.now() / 1000),  // Unix seconds, NOT milliseconds
});

console.log("User identified in Customer.io");

Key rules:

• id

  (first arg) should be your immutable database ID — never use email as ID

• email

  attribute is required if you want to send email campaigns

• created_at

  must be Unix timestamp in seconds (not ms) —

  Math.floor(Date.now() / 1000)

• All custom attributes are stored on the user profile and usable in segments + Liquid templates

Step 2: Track an Event

// Track a custom event on the user's activity timeline.
// Events trigger campaigns — the event name must match exactly in the dashboard.
await cio.track("user-123", {
  name: "signed_up",                   // snake_case, matches campaign trigger
  data: {
    signup_method: "google_oauth",
    referral_source: "product_hunt",
    timestamp: Math.floor(Date.now() / 1000),
  },
});

console.log("Event tracked in Customer.io");

Key rules:

• User must be identified before tracking events (call

  identify()

  first)
• Event

  name

  is case-sensitive and must match your campaign trigger exactly
• Use

  snake_case

  for event names —

  signed_up

  , not

  Signed Up

  or

  signedUp

• data

  properties are accessible in Liquid templates as

  {{ event.property_name }}

Step 3: Track an Anonymous Event

// Track events before the user signs up — merge later on identification
await cio.trackAnonymous({
  anonymous_id: "anon-abc-123",         // Your anonymous tracking ID (cookie, device ID)
  name: "page_viewed",
  data: {
    url: "/pricing",
    referrer: "https://google.com",
  },
});

console.log("Anonymous event tracked");

When the anonymous user signs up, include

anonymous_id

identify()

await cio.identify("user-123", {
  email: "hello@example.com",
  anonymous_id: "anon-abc-123",         // Merges anonymous activity
});

Step 4: Send a Transactional Email

import { APIClient, SendEmailRequest, RegionUS } from "customerio-node";

const api = new APIClient(process.env.CUSTOMERIO_APP_API_KEY!, {
  region: RegionUS,
});

const request = new SendEmailRequest({
  to: "hello@example.com",
  transactional_message_id: "1",        // ID from Customer.io dashboard
  message_data: {                       // Populates {{ liquid }} variables
    welcome_name: "Jane",
    login_url: "https://app.example.com/login",
  },
  identifiers: { id: "user-123" },      // Links delivery to user profile
});

const response = await api.sendEmail(request);
console.log("Email queued:", response.delivery_id);

Step 5: Verify in Dashboard

1. Go to https://fly.customer.io
2. Navigate to People and search for "hello@example.com"
3. Verify the profile shows

   first_name

   ,

   plan

   , and other attributes
4. Click the Activity tab to see the

   signed_up

   event
5. Check Deliveries for the transactional email

Complete Example

// scripts/hello-customerio.ts
import {
  TrackClient, APIClient, SendEmailRequest, RegionUS
} from "customerio-node";

async function main() {
  // Track API client — identify and track
  const cio = new TrackClient(
    process.env.CUSTOMERIO_SITE_ID!,
    process.env.CUSTOMERIO_TRACK_API_KEY!,
    { region: RegionUS }
  );

  // 1. Identify
  await cio.identify("user-hello-world", {
    email: "hello@example.com",
    first_name: "Jane",
    created_at: Math.floor(Date.now() / 1000),
  });
  console.log("1. User identified");

  // 2. Track event
  await cio.track("user-hello-world", {
    name: "hello_world_completed",
    data: { sdk: "customerio-node", step: "quickstart" },
  });
  console.log("2. Event tracked");

  // 3. Clean up test user (optional)
  await cio.suppress("user-hello-world");
  console.log("3. Test user suppressed (won't receive messages)");
}

main().catch(console.error);

Run:

npx tsx scripts/hello-customerio.ts

Error Handling

401 Unauthorized

400 Bad Request

identify()

identify()

track()

transactional_message_id

Resources

• Track API Reference
• Transactional API Concepts
• customerio-node README

Next Steps

After verifying hello world works, proceed to

customerio-local-dev-loop