What the heck is Middleware?

Middleware is like the friendly helper of your website. It's the one who makes sure everything goes smoothly when someone interacts with your website. To put it simply, middleware is like the gatekeeper at a club who checks IDs to decide who can come in.

How it works:

1. Setting Things Up: Before your website even realizes it, middleware starts getting things ready behind the scenes.

2. Custom Rules: Depending on the request (or the person at the club's door), middleware can do different things. It can change where the request goes, send it somewhere else, or adjust how your website responds.

3. File Location: To use middleware, you usually put a file called middleware.ts or middleware.js right in your project's main folder, where all the important stuff is.

Let's See an Example

Imagine someone wants to visit the "about" page on your website. With middleware, you can send them to a different page called "home" instead. Here's how you can do it:

import { NextResponse } from 'next/server'
import type { NextRequest } from 'next/server'

export function middleware(request: NextRequest) {
  return NextResponse.redirect(new URL('/home', request.url))
}

Matching Path

Middleware is like a well-organized secretary that handles different tasks in a specific order:

• First, it checks headers from next.config.js.

• Then, it follows any redirects set in next.config.js.

• Middleware does its magic, which includes rewriting and redirecting.

• It looks at special rules in next.config.js for rewriting files.

• Your website's file system, including public, static, and pages, comes into play.

• More file rewriting happens as per next.config.js.

• Dynamic routes (the ones with slugs) get their turn.

• If none of the above fits, there's one last chance to rewrite it in next.config.js.

You can tell middleware which paths to pay attention to in two ways:

1. Custom Matcher Config: You can be very specific about which paths you want
   middleware to keep an eye on. For example:

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

1. Conditional Statements: You can use code to decide. If a request starts with "/about," you do one thing, and if it starts with "/dashboard," you do something else.

import { NextResponse } from 'next/server'
import type { NextRequest } from 'next/server'

export function middleware(request: NextRequest) {
  if (request.nextUrl.pathname.startsWith('/about')) {
    return NextResponse.rewrite(new URL('/about-2', request.url))
  }

  if (request.nextUrl.pathname.startsWith('/dashboard')) {
    return NextResponse.rewrite(new URL('/dashboard/user', request.url))
  }
}

Why and When to Use Middleware

Why Use Middleware?

Middleware is a powerful tool for tailoring your website's behavior to different scenarios. You can use it to:

• Make your website safer. It's like having a guard at the door to check IDs before letting people in.

• With middleware, you can change how your website responds to each person. It's like giving each visitor a unique experience.

• You can use middleware to direct visitors to different pages based on what they want. It's like showing them the right way to go.

• It helps you with messages between your website and visitors. You can use it to set cookies or to make things more secure.

When to Use Middleware?

You should consider using middleware when:

• You need to add an extra layer of security to your website by checking user credentials before granting access to certain routes.

• You want to create a dynamic and personalized user experience by changing how your website responds to different requests.

• Redirecting users based on specific conditions is necessary, such as sending them to a different page when they hit a certain URL.

• You require control over request and response headers, like setting cookies or enhancing security measures.

Conclusion

Middleware is like your app's behind-the-scenes helper, making sure everything runs smoothly. It's a powerful tool to customize how your app behaves for different requests and situations.