Customer.io Install & Auth

Overview

Set up the customerio-node SDK and configure authentication for Customer.io's two API surfaces: the Track API (identify users, track events) and the App API (transactional messages, broadcasts, data queries).

Prerequisites

• Node.js 18+ with npm/pnpm
• Customer.io account at https://fly.customer.io
• Site ID + Track API Key from Settings > Workspace Settings > API & Webhook Credentials
• App API Key (bearer token) from the same page — needed for transactional messages and broadcasts

Two API Keys, Two Clients

Instructions

Step 1: Install the SDK

npm install customerio-node

The package exports TrackClient, APIClient, RegionUS, RegionEU, SendEmailRequest, and SendPushRequest.

Step 2: Configure Environment Variables

# .env — NEVER commit this file
CUSTOMERIO_SITE_ID=your-site-id-here
CUSTOMERIO_TRACK_API_KEY=your-track-api-key-here
CUSTOMERIO_APP_API_KEY=your-app-api-key-here
CUSTOMERIO_REGION=us          # "us" or "eu"

Add .env to .gitignore if not already there.

Step 3: Create the Track Client

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

function getRegion() {
  return process.env.CUSTOMERIO_REGION === "eu" ? RegionEU : RegionUS;
}

// Singleton — reuse across your app
let trackClient: TrackClient | null = null;

export function getTrackClient(): TrackClient {
  if (!trackClient) {
    const siteId = process.env.CUSTOMERIO_SITE_ID;
    const apiKey = process.env.CUSTOMERIO_TRACK_API_KEY;
    if (!siteId || !apiKey) {
      throw new Error(
        "Missing CUSTOMERIO_SITE_ID or CUSTOMERIO_TRACK_API_KEY"
      );
    }
    trackClient = new TrackClient(siteId, apiKey, { region: getRegion() });
  }
  return trackClient;
}

Step 4: Create the App API Client

// lib/customerio-app.ts
import { APIClient, RegionUS, RegionEU } from "customerio-node";

let appClient: APIClient | null = null;

export function getAppClient(): APIClient {
  if (!appClient) {
    const appKey = process.env.CUSTOMERIO_APP_API_KEY;
    if (!appKey) {
      throw new Error("Missing CUSTOMERIO_APP_API_KEY");
    }
    const region =
      process.env.CUSTOMERIO_REGION === "eu" ? RegionEU : RegionUS;
    appClient = new APIClient(appKey, { region });
  }
  return appClient;
}

Step 5: Verify Connection

// scripts/verify-customerio.ts
import { getTrackClient } from "../lib/customerio";

async function verify() {
  const cio = getTrackClient();
  try {
    // Identify a test user — if credentials are wrong, this throws
    await cio.identify("test-verify-user", {
      email: "verify@example.com",
      created_at: Math.floor(Date.now() / 1000),
    });
    console.log("Customer.io connection verified successfully");
    // Clean up: suppress the test user
    await cio.suppress("test-verify-user");
    console.log("Test user suppressed");
  } catch (err: any) {
    console.error("Connection failed:", err.statusCode, err.message);
    process.exit(1);
  }
}

verify();

Run with: npx tsx scripts/verify-customerio.ts

Region Configuration

Your region is set when you create your Customer.io account. Check Settings > Workspace Settings to confirm. EU accounts must specify RegionEU or all API calls will fail with 401.

Error Handling

Security Notes

• Store credentials in a secrets manager (GCP Secret Manager, AWS SSM, Vault) for production
• Track API Key can identify/track users but cannot send messages — lower risk
• App API Key can send messages and access data — treat as highly sensitive
• Rotate keys every 90 days via Settings > API & Webhook Credentials > Regenerate

Resources

• Managing API Credentials
• Account Regions (US and EU)
• Track API Reference
• App API Reference
• customerio-node on GitHub

Next Steps

After successful auth, proceed to customerio-hello-world for your first identify + track call.