Deploying to Vercel Edge

Edge Runtime brings your code closer to users. Here's how to use it effectively with Next.js.

What is Edge Runtime?

Edge functions run on Vercel's global network — not in a single region like traditional serverless. This means lower latency for users worldwide.

// app/api/geo/route.ts
export const runtime = "edge";

export function GET(request: Request) {
  const country = request.headers.get("x-vercel-ip-country") ?? "unknown";
  return Response.json({ country });
}

Edge vs Node.js Runtime

Middleware

Middleware always runs on the Edge. Use it for auth checks, redirects, and A/B testing:

// middleware.ts
import { NextResponse } from "next/server";
import type { NextRequest } from "next/server";

export function middleware(request: NextRequest) {
  const session = request.cookies.get("session");

  if (request.nextUrl.pathname.startsWith("/admin") && !session) {
    return NextResponse.redirect(new URL("/login", request.url));
  }

  return NextResponse.next();
}

export const config = {
  matcher: ["/admin/:path*"],
};

Limitations to Know

1. No native Node.js modules — fs, path, crypto (use Web Crypto instead)
2. Max 1MB bundle size per function
3. No long-running connections — WebSockets work, but with 30s timeout
4. Limited npm support — many packages depend on Node.js APIs

When to Use Edge

• Authentication / authorization middleware
• Geolocation-based content
• A/B testing
• Simple API responses (JSON)
• Header/cookie manipulation