ServiceStack vs ASP.NET Core: What are the differences?
ServiceStack: A configuration free, code-first, light-weight framework *. It is a configuration free, code-first, light-weight framework built on top of ASP.NET for building services and web applications. As the name suggests, it is a stack of services. It provides with just everything that one needs for building end-to-end web services; *ASP.NET Core:** A cross-platform .NET framework for building modern cloud-based web applications on Windows, Mac, or Linux. A free and open-source web framework, and higher performance than ASP.NET, developed by Microsoft and the community. It is a modular framework that runs on both the full .NET Framework, on Windows, and the cross-platform .NET Core.
ServiceStack and ASP.NET Core belong to "Frameworks (Full Stack)" category of the tech stack.
ASP.NET Core is an open source tool with 13.6K GitHub stars and 3.34K GitHub forks. Here's a link to ASP.NET Core's open source repository on GitHub.