# H5: The C# to JavaScript Compiler

Build the modern web with the language you love. H5 brings the full power, type safety, and productivity of C# directly to the browser.

# Why H5?

# 🚀 C# Power, JavaScript Reach

Write your application logic, UI components, and complex algorithms in C#. H5 compiles your code into clean, high-performance JavaScript that runs in any browser, on any device—from mobile to desktop.

# 🛡️ Real Type Safety

Eliminate "undefined is not a function" forever. Leverage C#’s strong typing, generics, and compile-time checks to catch errors before they ever reach your users.

# 📦 Seamless Ecosystem Integration

Don't choose between .NET and JavaScript. Use h5.Core to access the full DOM and ES5/6+ APIs, or integrate your favorite npm libraries like React, Vue, or jQuery with ease.

# ⚡ Built for Performance

H5 features a hosted compiler process that speeds up your development cycle. It produces human-readable, optimized JavaScript and full sourcemaps, making debugging in the browser as easy as debugging in Visual Studio.

# Write C#. Run Everywhere.

H5 transforms your C# classes into optimized JavaScript structures while maintaining the logic and behavior you expect from the .NET runtime.

# The C# Source

public class TodoItem
{
    public int Id { get; set; }
    public string Task { get; set; }
    public bool IsDone { get; set; }

    public void Toggle()
    {
        this.IsDone = !this.IsDone;
        Console.WriteLine($"Task {Id} is now {(IsDone ? "done" : "pending")}");
    }
}

# The H5 Output

H5.define("App.TodoItem", {
    props: {
        Id: 0,
        Task: null,
        IsDone: false
    },
    methods: {
        Toggle: function () {
            this.IsDone = !this.IsDone;
            System.Console.WriteLine("Task " + this.Id + " is now " + (this.IsDone ? "done" : "pending"));
        }
    }
});

# Modern Tooling for Modern Devs

H5 is built for the current .NET ecosystem, fitting perfectly into your existing workflow.

Standardized: Projects target .NET Standard 2.1, enabling compatibility with shared back-end projects.
CLI First: The compiler is distributed as a dotnet global tool, making CI/CD and automation effortless.
SDK-Style: No more legacy .csproj bloat. H5 uses modern, clean SDK-style project files.
IDE Support: Full Intellisense and statement completion in Visual Studio and VS Code.

# Powerful Extensions

Expand your capabilities with purpose-built H5 packages:

h5: Core library providing a .NET-equivalent runtime for the browser.
h5.Core: Core library providing strongly typed bindings for the HTML5 API.
h5.Newtonsoft.Json: JSON serialization support in the browser with a Newtonsoft.Json style API.
h5.WebGL2: Build high-performance 3D games and visualizations using C#.

# Get Started in Seconds

H5 is available via NuGet and the dotnet CLI.

1. Install the H5 Compiler:

dotnet tool install -g h5-compiler

2. Create a new H5 project using a .NET template:

dotnet new install h5.Template
dotnet new h5 -n MyWebProject

3. Build and Run:

dotnet tool install --global dotnet-serve
dotnet build
dotnet serve .\bin\Debug\netstandard2.1\h5\

# Ready to build?

Download H5 on NuGet | View Documentation | Explore Samples

H5: The next generation of C# web development.