Is this C# playground free?

Yes. The editor, runtime and examples are free to use, and no account or payment method is required.

Is my C# code uploaded?

No. Code runs inside this browser tab. The sandbox blocks network access, and SkillAIVibe does not receive or store the code you type.

Free browser compiler

How the sandbox works, and its honest limits, is on the code execution and security page.

Roslyn 4.14.0 compiling for .NET 10.0.12 (Mono WebAssembly, interpreted)

Press Esc then Tab to move keyboard focus out of the code editor.

stdin (one value per line, read by Console.ReadLine())

Output will appear here after you run your code.

A blank editor is the hard place to start. The C# exercises hand you a program that already runs and ask you to change one thing.

Can I run C# code online here?: Yes. This page runs C# in your browser using Roslyn 4.14.0 compiling for .NET 10.0.12 (Mono WebAssembly, interpreted). Nothing needs to be installed.
Is this C# playground free?: Yes. The editor, runtime and examples are free to use, and no account or payment method is required.
Is my C# code uploaded?: No. Code runs inside this browser tab. The sandbox blocks network access, and SkillAIVibe does not receive or store the code you type.