Online C# Compiler

Write, run, and share code snippets - no setup required.

Program.cs

Alice
30

Output

Click Run to see the output here.

using System;

class Program {
    static void Main() {
        string name = Console.ReadLine();
        int age = int.Parse(Console.ReadLine());
        Console.WriteLine($"Hello, {name}! You are {age} years old.");
    }
}

Run C# online in your browser

A free online C# playground and compiler. Write C# in your browser, hit Run, and mcs compiles while Mono executes your program in seconds. No local .NET SDK, no Visual Studio, no dotnet CLI to set up first.

The editor is built on the same engine as VS Code, so C# syntax highlighting, autocompletion, and diagnostic squiggles all work. Code compiles with the Mono mcs compiler and runs on Mono 6.12 with the SGen garbage collector - useful for exploring LINQ, testing async/await, or prepping for a C# interview without scaffolding a csproj.

What makes this C# playground useful

Instant C# execution - write code, press Run, and see output from the online C# compiler in seconds, no dotnet CLI or csproj needed.
Full C# syntax highlighting, type-aware autocompletion, and clear mcs compile errors, powered by the same editor engine as VS Code.
Stdin input is supported. Console.ReadLine(), Console.Read(), and Console.In.ReadToEnd() all read from the playground's input box, so interactive C# programs work end-to-end. No .NET SDK, Visual Studio, Rider, or Mono on your machine.
Mono 6.12 with the mcs compiler - write C# programs, use LINQ, generics, and async/await without installing the .NET SDK.

What you can build in the C# playground

LINQ queries: Where, Select, GroupBy, Aggregate over arrays and lists, with the compiler validating your lambdas.
Classes, interfaces, generics, and pattern matching: core C# idioms you can test one method at a time.
Quick C# experiments: try an extension method, test an async Task, verify a tuple deconstruction, or confirm how a nullable type flows.

Online C# compiler FAQ

Is the online C# compiler free?

Yes, the online C# playground is free to use. No sign-up, no .NET SDK to install, and no Visual Studio license to buy - open the page and compile.

Do I need the .NET SDK or Visual Studio installed?

No install needed. You don't need dotnet, Visual Studio, Rider, or Mono on your machine. The online C# compiler compiles with mcs and runs your program on Mono 6.12 in seconds.

Does the C# playground work on mobile and Chromebooks?

Yes. The C# playground runs in any modern browser, on desktop, tablet or mobile. Good for running C# from a Chromebook or a machine where you can't install the .NET SDK.

Can I use Console.ReadLine() in the online C# compiler?

Yes. Console.ReadLine(), Console.Read(), and Console.In.ReadToEnd() all read your typed lines the same way they would when you run a compiled .exe locally at the terminal. Good for interview problems that parse lines into arrays of ints.

How do I learn C# after trying the playground?

Edit the sample C# code, press Run, and iterate. When you want something more structured, Coddy's interactive C# course covers classes, LINQ, generics, async/await, and more with hands-on exercises.

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Free, browser-based tools that pair well with the C# Playground - all part of Coddy.

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