C# is a statically typed, object-oriented language developed by Microsoft and built to run on the .NET platform. Modern C# supports a mix of programming styles, including object-oriented and functional patterns, along with features like async/await for asynchronous code, LINQ for querying collections, and nullable reference types to catch null-related bugs at compile time. Since .NET became cross-platform and open source, C# code now runs natively on Windows, Linux, and macOS, which has broadened its use well beyond the Windows desktop and enterprise software it was historically associated with.
The language is commonly used for backend services, desktop applications, game development through engines like Unity and Godot, and enterprise line-of-business software. Its combination of strong typing, a large standard library, and a mature tooling ecosystem, including Visual Studio and the dotnet CLI, makes it a practical choice for teams that want compiled performance with a more approachable syntax than C or C++. Async support in particular makes C# well suited to I/O-heavy backend services that need to handle many concurrent requests efficiently.
Open-source projects using C# tend to be either .NET ecosystem tools themselves or applications that benefit from cross-platform desktop or server deployment. Jellyfin, the self-hosted media server featured on this page, is built primarily in C# and runs its backend across Windows, Linux, macOS, and even lower-powered devices like the Raspberry Pi. Ansible, primarily written in Python, also includes small C# and related .NET helper utilities used by some of its Windows automation modules.