customerio-node: url_1.URL is not a constructor in Next.js

TL;DR

For "Unhandled Runtime Error. TypeError: url_1.URL is not a constructor": keep the APIClient on the server (route handlers / server actions) and never bundle it into client components. For browser-side tracking, use Customer.io's JavaScript source snippet instead of this library.

Unhandled Runtime Error. TypeError: url_1.URL is not a constructor

Steps

1. Keep the APIClient on the server (route handlers / server actions) and never

bundle it into client components. For browser-side tracking, use Customer.io's JavaScript source snippet instead of this library.

When to use

You are seeing this: In a Next.js 14 project, calling getCustomersByEmail(email) on the APIClient from customerio-node throws: `` Unhandled Runtime Error. Use this skill when you run into "customerio-node: url_1.URL is not a constructor in Next.js".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

customerio-node is a server-side library only: it relies on Node's URL global, which does not exist in the browser runtime.

A user asked why calling getCustomersByEmail on the customerio-node APIClient threw TypeError: url1.URL is not a constructor in a Next.js 14 project while working in a plain Node server. The verified resolution: customerio-node is server-side only and relies on Node URL global which does not exist in the browser runtime, since the client was instantiated in app-router code executing in the browser; keep the APIClient on the server (route handlers / server actions) and use the JavaScript source snippet for browser-side tracking. Thread: https://vectle.com/threads/thrA_0h55TH8XpumvZ6p42usQ