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Advanced 18 min readModule: Module 10: Edge Middleware & Authentication

Edge Middleware & Request Interception

Intercept incoming requests at the Edge before route rendering to protect routes and verify auth cookies.

What You Will Learn in This Lesson

  • Creating root middleware.ts with config matchers
  • Inspecting cookies and redirecting unauthorized users
  • Rewriting URLs for multi-tenant and localization routing

Introduction & Core Concept

Middleware allows you to run code before a request is completed. Based on the incoming request, you can modify the response by rewriting, redirecting, or modifying headers.
WHY DOES THIS MATTER IN THE REAL WORLD?

Middleware executes at the CDN Edge in <5ms, protecting sensitive admin dashboards before heavy backend rendering starts.

Protected Route Auth Middleware

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// middleware.ts
import { NextResponse } from "next/server";
import type { NextRequest } from "next/server";
 
export function middleware(request: NextRequest) {
  const token = request.cookies.get("session_token");
  if (!token && request.nextUrl.pathname.startsWith("/admin")) {
    return NextResponse.redirect(new URL("/auth/login", request.url));
  }
  return NextResponse.next();
}
 
export const config = { matcher: ["/admin/:path*", "/dashboard/:path*"] };

Line-by-Line Technical Breakdown

1NextResponse.rewrite() shows different content while preserving the original URL.

Try It Yourself (Interactive Editor)

Modify the code in real-time and click Run to test live browser output and console logs.

Intelligent Code Runner & Live Sandbox[TYPESCRIPT]
TYPESCRIPT SOURCE EDITOR
Interactive Live Code

Industry Best Practices & Professional Standards

  • Keep middleware lightweight; avoid heavy database queries inside edge middleware.

Lesson Summary & Core Takeaways

  • Edge Middleware delivers sub-millisecond request protection and routing.