Middleware in Laravel are filters that inspect or modify HTTP requests and responses. They perform tasks like checking user authentication, logging request details, handling CORS, and adding response headers. Common uses include authentication checks, debugging, and modifying responses. To apply middleware, define it via Artisan, register it in Kernel.php, then apply it to routes or controllers. Create custom middleware when logic repeats across routes or handles cross-cutting concerns, ensuring each middleware focuses on a single task for better organization.

In Laravel, middleware are like filters that sit between a request and the rest of your application. Their main job is to inspect or modify incoming HTTP requests before they reach your routes or controllers — or to tweak the response before it gets sent back to the user.

What do middleware actually do?

You can think of middleware as a series of checks or actions that happen every time someone visits your app. For example:

• Check if a user is logged in
• Add headers to a response
• Log request details
• Handle CORS (Cross-Origin Resource Sharing)

They help you organize logic that shouldn’t live directly in your controller — things that should run for many routes, not just one.

Common uses for middleware

Middleware shines when you need something to run across multiple routes or under certain conditions.

Authentication check

This is probably the most common use. Before letting a user access a route, middleware checks if they’re logged in or have the right permissions.

Example: You might apply an auth middleware to any route that requires login. If the user isn’t authenticated, they get redirected to the login page.

Logging or debugging

You can create middleware that logs request data — useful for debugging or monitoring traffic.

For instance:

• Record how long a request takes
• Save the user’s IP address
• Track which endpoints are used most often

These kinds of tasks don’t belong in a controller, but middleware makes them easy to manage.

Modifying responses

Sometimes you want to tweak the outgoing response. Maybe you want to add extra headers or inject some debug info in development mode.

An example would be adding a custom header like X-Powered-By: Laravel to all responses — just drop it into a middleware and apply it where needed.

How to apply middleware in Laravel

Applying middleware is straightforward once you understand the flow.

Define your middleware

First, create a middleware using Artisan:

php artisan make:middleware CheckAge

Inside the generated file, you’ll write the logic — like checking if a user is over 18.

Register it in Kernel.php

Next, register it in app/Http/Kernel.php. There, you can assign it a name like 'adult'.

Apply it to routes

Now you can apply it to specific routes:

Route::get('/movies', [MovieController::class, 'index'])->middleware('adult');

Or apply it at the controller level:

public function __construct()
{
    $this->middleware('adult');
}

You can also apply middleware conditionally — only for certain methods or with parameters.

When to create custom middleware

Creating custom middleware makes sense when you find yourself repeating logic across multiple controllers or routes.

Some signs you should make a middleware:

• You're writing the same check in multiple controller methods
• You're modifying requests or responses globally
• You're handling cross-cutting concerns like logging, security, or rate limiting

It’s not always obvious when to pull something out into middleware, but a good rule of thumb is: if it affects more than one route and isn't core business logic, consider middleware.

Also, keep each middleware focused on one thing. Don’t try to handle authentication, logging, and caching all in one — split them up so each one does one job well.

Basically, middleware in Laravel are tools that help you manage what happens before and after a request is handled. They help clean up your code and keep logic organized without cluttering controllers or routes.

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