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Online C# Playground

Runs on Mono 6.6.0.161 · Free · No signup required

A free online C# playground and compiler for backend engineers. Write C#, compile it, and run it in your browser — no Visual Studio, no SDK install, no project file, no signup. It is built for quick verification rather than application development: checking how LINQ evaluates a query, confirming what a nullable reference does at runtime, testing string formatting, or practising interview problems without launching a full IDE. Compilation happens server-side, so the errors you see are real compiler output rather than editor hints. Standard input is supported for programs that read from the console. Programs run as single files against the standard library. If you are building backend services with .NET and want structured practice rather than one-off snippets, the playground pairs with our backend engineering courses and projects.

C# Playground — Frequently Asked Questions

Do I need Visual Studio or the .NET SDK?
No. Everything compiles and runs on our servers. You need only a browser.
Can I use ASP.NET or NuGet packages?
No. The playground compiles single-file programs against the standard library.
Does Console.ReadLine work?
Yes. Standard input is supported, so console-reading programs behave normally.

Try another language

Ready to build real backends rather than test snippets? Explore backend engineering courses and projects at MasteringBackend.