vercel-edge-functions

name	vercel-edge-functions
description	Build and deploy Vercel Edge Functions for ultra-low latency at the edge. Use when creating API routes with minimal latency, geolocation-based routing, A/B testing, or authentication at the edge. Trigger with phrases like "vercel edge function", "vercel edge runtime", "deploy edge function", "vercel middleware", "@vercel/edge".
allowed-tools	Read, Write, Edit, Bash(vercel:*), Bash(npm:*), Grep
version	1.18.0
license	MIT
author	Jeremy Longshore <[e-mail]>
tags	["saas","vercel","edge","serverless","performance"]
compatibility	Designed for Claude Code

Vercel Edge Functions

Overview

Edge Functions run on Vercel's Edge Network (V8 isolates) close to the user with no cold starts. They use Web Standard APIs (Request, Response, fetch) instead of Node.js APIs. Ideal for authentication, A/B testing, geolocation routing, and low-latency API responses.

Prerequisites

• Completed vercel-install-auth setup
• Familiarity with Web APIs (Request/Response)
• Node.js 18+ for local development

Instructions

Step 1: Create an Edge Function

// api/edge-hello.ts
// Export `runtime = 'edge'` to run on the Edge Runtime
export const config = { runtime: 'edge' };

export default function handler(request: Request): Response {
  return new Response(
    JSON.stringify({
      message: 'Hello from the Edge!',
      region: request.headers.get('x-vercel-ip-city') ?? 'unknown',
      timestamp: Date.now(),
    }),
    {
      status: 200,
      headers: { 'Content-Type': 'application/json' },
    }
  );
}

Step 2: Edge Function with Geolocation

Vercel injects geolocation headers into every edge request:

// api/geo.ts
export  config = { :  };

   ():  {
   city = request..() ?? ;
   country = request..() ?? ;
   region = request..() ?? ;
   latitude = request..();
   longitude = request..();

   .({
    : (city),
    country,
    region,
    : latitude && longitude ? { : latitude, : longitude } : ,
  });
}