What is it

Middleware intercepts request or response before they are passed to application's core code.

• e.g. authentication to verify a user's identity before granting access.

Then, based on the incoming request, you can modify the response by rewriting, redirecting, modifying the request or response headers, or responding directly

• Middleware runs before cached content and routes are matched

How is it used

You can set CORS headers in Middleware to allow cross-origin requests

• including preflight and simple requests

Where to Place it

Use the file middleware.ts in the root of your project to define Middleware

• For example, at the same level as pages or app, or inside src if applicable

matcher

matcher allows you to filter Middleware to run on specific paths

• you can also use regex

export const config = {
  matcher: [
    '/about/:path*', 
    '/dashboard/:path*'
  ],
}