C# playground (compiler explorer) which runs entirely in a browser (via WebAssembly). Started as an alternative to SharpLab which is not maintained anymore. But it can also do some other stuff that I wanted like downloading any compiler version, and compiling Razor. Recently I've added some "IntelliSense" features to improve the editing experience.
https://lab.razor.fyi/
GitHub: https://github.com/jjonescz/DotNetLab