The ASP.NET Core middleware pipeline is the backbone of every HTTP request your application processes. Yet most developers only scratch the surface—registering UseAuthentication() and UseAuthorization() without understanding what actually happens in between. This comprehensive guide takes you from fundamental concepts to advanced patterns, performance optimization, and real-world usage scenarios. What is ASP.NET Middleware? Middleware in ASP.NET Core is software that's assembled into an app pipeline to handle requests and responses. Each middleware component: Chooses whether to pass the request to the next middleware Can perform work before and after the next middleware Can short-circuit the pipeline entirely Think of it as an assembly line: each station does one specific job (logging, authentication, CORS headers, compression), and the request moves from station to station. The response then travels back through the same chain in reverse order.…