Functions API Reference

Vercel Functions use a Web Handler, which consists of the request parameter that is an instance of the web standard Request API, and for non-Next.js apps, a context parameter that represents the context of the request. Next.js extends the standard Request object with additional properties and methods.

To use a Web Handler, you must be using Node.js 18 or later. If you are using an earlier version, you must use the Node.js signature.

export const dynamic = 'force-dynamic'; // static by default, unless reading the request
 
export function GET(request: Request) {
  return new Response(`Hello from ${process.env.VERCEL_REGION}`);
}

The waitUntil() method enqueues an asynchronous task to be performed during the lifecycle of the request. You can use it for anything that can be done after the response is sent, such as logging, sending analytics, or updating a cache, without blocking the response from being sent.

To use waitUntil() in your function:

1. Install the @vercel/functions package:

pnpm i @vercel/functions

2. Import the @vercel/functions package, which exposes the waitUntil() method:

import { waitUntil } from '@vercel/functions';
 
export function GET() {
  const country = request.headers.get('x-vercel-ip-country');
  // Returns a response immediately while keeping the function alive
  waitUntil(fetch(`https://api.vercel.app/countries/?incr=${country}`));
  return new Response(`You're visiting from beautiful ${country}`);
}

waitUntil() can be also used with the Edge Runtime.

The promises passed to waitUntil() will have the same timeout as the function itself. If the function times out, the promises will be cancelled.

export const runtime = 'nodejs';
export const maxDuration = 15;