What is Laravel middleware pipeline architecture and how does it work internally?

Laravel middleware pipeline processes HTTP requests through a layered chain before reaching controllers.

Laravel middleware is implemented as a pipeline where each middleware receives the request, performs logic, and either passes it forward or short-circuits it. Internally, Laravel uses a Pipeline class to sequentially execute middleware. This design follows the Chain of Responsibility pattern. Middleware can handle authentication, logging, CORS, throttling, and request modification. The order of middleware matters because each layer can mutate or block the request.