CORS error on Messenger widget in Next.js SSR

NICE CXone API & Integrations
1

Configuration is broken for some reason when embedding the widget in a Next.js 14 app.

widget:
 client_id: ${GENESYS_CLIENT_ID}
 origin: https://app.example.com
 allowed_origins: ['https://app.example.com', 'https://staging.app.example.com']

The browser blocks the fetch to /api/v2/webmessaging/v1/conversations with a 403 CORS error. The header looks correct in Postman but fails in the client-side render. What am I missing?

2

This has the hallmarks of a classic Next.js hydration mismatch. The widget script loads before the client-side origin matches the allowed origins list in your Genesys Cloud Org settings.

In Next.js 14, next/dynamic with ssr: false is mandatory for the widget script. If you render it on the server, the origin check fails because the server environment doesn’t match your allowed_origins.

Add this to your layout:

import dynamic from 'next/dynamic';

const MessengerWidget = dynamic(() => import('@/components/MessengerWidget'), {
 ssr: false,
 loading: () => <p>Loading chat...</p>,
});

export default function Layout({ children }) {
 return (
 <html>
 <body>
 {children}
 <MessengerWidget />
 </body>
 </html>
 );
}

Ensure your allowed_origins in the Genesys admin console exactly matches the runtime origin. No wildcards. Verify the client_id in your env vars. The 403 is likely the API rejecting the preflight because the script didn’t initialize with a valid token context from the correct origin. Check the network tab for the Origin header.

3

You need to ensure the origin matches the server-side request header exactly, not just the frontend URL.

{
 "client_id": "your_client_id",
 "origin": "https://app.example.com",
 "allowed_origins": [
 "https://app.example.com"
 ]
}