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Uno/UX compiler

AppVeyor build status NPM package NPM beta License: MIT Slack Financial Contributors on Open Collective

Target platforms Host platforms

Extremely fast, native C#-dialect and powerful tooling for mobile and desktop developers.

Welcome to Uno, the core component in Fuse Open, a native app development tool suite.


$ npm install @fuse-open/uno

This will install the uno command and standard library.

Beta releases

We are currently working on beta-3.0. Releases made from this branch are tagged @beta on NPM.

Related packages


Uno is a collection of compiler and platform abstraction technologies.

Uno is used on Linux, macOS and Windows, and makes native apps for the following platforms:

Platform Build targets
Android android, android-emu
iOS ios, ios-sim
Linux native, dotnet
macOS native, dotnet
Windows native, dotnet

Uno syntax

class Program
    static void Main()
        debug_log "Hello, World!";

The Uno programming language is a fast, native dialect of C# that can cross-compile to any native platform (in theory), by emitting portable C++17 for mobile or desktop platforms, or CIL bytecode for desktop platforms (Mono/.NET) — designed for developing high-performance UI-engines, platform abstractions or integrations, and other kinds of software traditionally required written in native C/C++.

Access all APIs and features on the target platforms directly in Uno — add a snippet of foreign code, and our compiler automatically generates the glue necessary to interoperate (two-way) with a foreign language. The following foreign languages are supported:

Run-time features

  • Memory in Uno is managed semi-automatically by automatic reference counting, avoiding unpredictable GC stalls.
  • Real generics – sharing the same compiled code in all generic type instantiations, without boxing values, and with full run-time type system support – avoiding exploding code-size and compile-times (while still being fast).
  • (Opt-in) reflection on all platforms – to dynamically create objects and invoke methods based on type information only known at run-time – enabling high-level Fuse features such as live-previewing UX documents.

Please see our documentation for information about building apps.

Build Instructions

Uno is built using the command-line on Linux, macOS or Windows – or from inside an IDE.

make install
uno --version

Please see the build instructions for details on how to build the source code.


Please see the configuration reference documentation for details on how to set up uno's configuration files for your build-environment.

Command Line Reference

Please see the command-line reference documentation for details on how to use uno's command-line interface.


Please see CONTRIBUTING for details on our code of conduct, and the process for submitting pull requests to us.

Reporting issues

Please report issues here.


Code Contributors

This project exists thanks to all the people who contribute. [Contribute]

Financial Contributors

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