01 / CLOSED WORLD
Unused means gone.
Only reachable code, data, generics, and imports survive. An unused package reference does not become deployment baggage.
Independent .NET. Built outside Microsoft.
The new Mono.
Built for Wasm.
Mono proved .NET could belong beyond one company. NetWasm brings that independent spirit to the Wasm era—compiling your reachable C# program into one standalone WebAssembly Component.
Live Playground · No account · Your browser does the compiling
C# 15 · 5 development hosts: Linux x64 and ARM64 · macOS ARM64 · Windows x64 and ARM64
hello-netwasm / Release
verified
FINAL COMPONENT
91,294
bytes
- ✓ C# application
- ✓ Precise garbage collector
- ✓ Runtime included
- ✓ Uncompressed
NO CLR.
NO MONO RUNTIME.
NO dotnet.js.
NO APP DLLs.
An independent .NET again
Mono proved .NET could be bigger than one company.
THE NEXT INDEPENDENT IMPLEMENTATION
starts with Wasm.
Mono is now part of Microsoft. NetWasm brings back an ambitious .NET implementation built independently, in public, by one developer: compiler, CoreLib, runtime, precise GC, SDK, WASI host, browser toolchain, libraries, and test integration. JetBrains gave Kotlin a portable Wasm platform. This is C#’s answer.
The runtime tax is optional
Build with .NET.
Run without .NET.
Roslyn produces CIL. NetWasm compiles the reachable program directly to Wasm, specializes its generics, and links only the runtime support it actually uses. The component is the program.
01C#Your source
02CILRoslyn
03WasmNetWasm AOT
04One fileDeploy anywhere with WASI
AOT without the traps
AOT without linker-annotation whack-a-mole.
NetWasm works out what your program needs at compile time. JSON, Regex, dependency injection, and structured logging generate ordinary code the compiler can see—so your app does not break because somebody forgot a “do not trim this constructor” annotation three libraries away.
Try the generated-code examplesVISIBLE TO THE COMPILER
01JSON serializersgenerated code
02Regex enginesgenerated code
03DI activationgenerated code
04Logger messagesgenerated code
✓ Reachability decided at compile time
Smaller by design
Pay for the code you use.
Nothing else gets a free ride.
NetWasm starts with a smaller platform contract: closed-world compilation, precise GC, and explicit host capabilities. It does not drag desktop assumptions into every deployment.
02 / C# 15
Modern C#. Native Wasm.
C# 15, generics, exceptions, async, managed memory, and precise garbage collection compile into the final artifact.
03 / WASI
Capabilities are explicit.
Programs receive the clocks, HTTP, files, and host interfaces you choose—not ambient access to the machine.
04 / BOTH ADDRESS WIDTHS
wasm32 today. Memory64 when you need it.
Ship portable wasm32 WASI Preview 2 Components, or target raw wasm32 and wasm64 core modules for advanced hosts.
Not a toy compiler
The C# loop is already here.
Build, run, publish, test, and reuse focused libraries with the commands you already know.
dotnet build·dotnet run·dotnet publish·dotnet test
15
Focused libraries
LINQ and Async LINQ, Memory, Pipelines, Web Encodings, HTTP, Regex, JSON, XML, Hashing, reflection-free dependency injection, Options, and structured logging.
Explore libraries ↗ TTests that compile too
Run TUnit through ordinary dotnet test, with source-generated discovery and a NetWasm runner.
A compiler in your browser
Edit C#, compile it locally, run the result, compare optimization settings, and download the component.
Try it now — no install ↗Local quickstart
Try the real thing.
Install .NET SDK 10.0.300 or newer, create an app, run it locally, and publish a standalone component. Use the .NET 11 SDK when your source uses C# 15.
Five supported development hosts: Linux x64, Linux ARM64, macOS ARM64, Windows x64, and Windows ARM64. NuGet downloads the pinned host tools on first restore and reuses them on later builds. No separate Emscripten, Node.js, Python, Git, LLVM, or Binaryen setup is needed.
Read the full quickstart ↗$ dotnet new install NetWasm.Templates
$ dotnet new netwasm-app -n HelloNetWasm
$ cd HelloNetWasm
$ dotnet run
42
$ dotnet publish -c Release -o publish/localStop reading. Compile something.
Your C#.
One Wasm file.
The Playground runs the compiler in your browser. Start with the C# 15 tour, then try JSON, Regex, dependency injection, generated logging, XML, HTTP, LINQ, hashing, or TUnit.
NetWasm 0.4 is ready for early adopters.
NetWasm is pre-1.0, so its API and ABI can evolve. The current profile deliberately excludes runtime reflection, dynamic, runtime assembly loading, managed threading, general managed file APIs, raw sockets, and subprocesses.