The Kestrel web server is Microsoft’s cross-platform HTTP server framework for ASP.NET Core runtime support. Kestrel runs on both Windows and Linux hardware to provide standardized compilation support for ASP.NET applications in production. In basic terms: Kestrel is the default web server for ASP.NET Core hosting. The open-source and cross-platform server is lightweight and fast but missing some functionality for ASP.NET Core hosting — your best bet is to pair it with IIS, NGINX, or Apache. An older ASP.NET application will work with Microsoft’s IIS web server platform, which functions similarly to Apache. The Kestrel server boasts faster performance for I/O requests when compared with IIS but does not provide solutions for tasks like port sharing, easy SSL configuration, and URL rewrites. That’s why most recommend using Kestrel with a full-service web server (like IIS, Apache, or NGINX) so it acts as a reverse proxy server for application hosting. Developers can use .NET CLI or Visual Studio to integrate Kestrel with ASP.NET Core, the .NET framework, and IIS, NGINX, or Apache according to their specific application hosting requirements.