Middleware

Learn how ASP.NET Core's middleware pipeline processes every request, and how to write your own middleware.

What is Middleware?

Middleware is a component that sits in the request pipeline, able to inspect, modify, or short-circuit a request before it reaches your controller — and do the same to the response on the way back out.

The Pipeline & Order

Middleware runs in the exact order it's registered in Program.cs — this order matters enormously.

Program.cs

app.UseHttpsRedirection();
app.UseAuthentication();
app.UseAuthorization();
app.MapControllers();

Request In

↓

HttpsRedirection

↓

Authentication

↓

Authorization

↓

Controller

↓

Response Out

Built-in Middleware

Middleware	Purpose
UseHttpsRedirection	Redirects HTTP requests to HTTPS
UseStaticFiles	Serves files from wwwroot (images, CSS, JS)
UseAuthentication	Identifies who the caller is
UseAuthorization	Checks whether that caller is allowed to proceed
UseCors	Controls which origins can call your API

Custom Middleware

You can write your own middleware for cross-cutting concerns like logging every request.

app.Use(async (context, next) =>
{
    Console.WriteLine($"Request: {context.Request.Method} {context.Request.Path}");
    await next(); // pass control to the next middleware
    Console.WriteLine($"Response: {context.Response.StatusCode}");
});

FAQs

What happens if I forget to call next()?

The pipeline short-circuits there — nothing after that middleware (including your controllers) will run for that request.

Summary

Middleware processes every request and response in a defined order.
Order matters — authentication must run before authorization, for example.
Custom middleware handles cross-cutting concerns like logging.

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