This function becomes directly callable from JavaScript.

July 7, 2026 · View on GitHub

Jazzy Desktop

Build modern desktop applications with Nim and your favourite web stack.

The desktop application framework for the Nim ecosystem — powered by Jazzy Framework under the hood.

Why Jazzy? • Features • Quick Start • Core Concepts • Native OS APIs • Web Mode • Roadmap

Why Jazzy Desktop?

The Nim ecosystem has GUI libraries — but they all make you think in widgets, layouts, and signals. It's 2026. Your users expect the web. Jazzy Desktop lets you build with the tools you already know: React, Vue, Svelte, plain HTML — anything that runs in a browser — while your backend is pure, compiled, blazing-fast Nim.

	NiGui	libui-ng (nim-libui)	fidget	Jazzy Desktop
UI Model	Native widgets	Native widgets	OpenGL canvas	Web (HTML/CSS/JS)
Frontend	Nim only	Nim only	Nim only	React / Vue / Svelte / anything
Styling	OS-native	OS-native	Custom	Full CSS, animations, glassmorphism
IPC	—	—	—	Zero-config RPC + WebSockets
Web Deploy	✗	✗	✗	✓ — same binary, zero changes
Hot-Reload	✗	✗	✗	✓

Native GUI toolkits are powerful, but they come with constraints. Jazzy Desktop removes those constraints: your UI is a first-class web application backed by a native Nim process, communicating over a local Jazzy HTTP server. You get the rendering power of the browser, the raw speed of Nim, and a zero-config bridge between them.

Features

✨ Zero-Config RPC

Write a Nim function, annotate it with {.expose.}, and call it from JavaScript like a local function. The macro takes care of routing, type validation, and serialization automatically.

⚡ Blazing-Fast Native Binary

Your backend compiles to native machine code via Nim's C/C++ transpiler. Tiny memory footprint, instant startup time.

🔄 Two-Way Real-Time Events

Push data from Nim to your frontend at any time using the built-in WebSocket event bus — no polling, no complexity.

🖥️ Full Native OS Integration

Window management, system tray, native file dialogs, clipboard, single-instance lock, and Windows 11 Mica glass effect — all accessible from JavaScript.

🌐 Deploy as a Web App

Compile your desktop app into a pure web server with the --web flag. Zero code changes required.

🗄️ Built-in Local Settings Store

A built-in store.nim module persists user preferences (theme, language, window size…) in OS-appropriate config directories — AppData/Roaming on Windows, Library/Application Support on macOS, ~/.config on Linux.

🔥 Hot-Reload Development

jazzyd dev watches both your Nim backend and Vite frontend simultaneously, restarting only what changed.

Quick Start

Prerequisites

Nim >= 2.0
Node.js (for the Vite frontend)
MinGW-w64 (Windows) or a standard C++ toolchain

1. Install

nimble install jazzy_desktop

2. Create a New Project

jazzyd new my-awesome-app
cd my-awesome-app

3. Start Development

jazzyd dev

Both the Nim backend and the Vite frontend start together with Hot-Reload. Edit any file and see changes reflected instantly.

4. Build for Production

jazzyd build

Produces a single, self-contained executable with all frontend assets embedded inside via Nim's compile-time VFS.

Core Concepts

The `{.expose.}` Macro — RPC Made Trivial

This is the heart of Jazzy Desktop. Any Nim proc annotated with {.expose.} is automatically registered as an RPC endpoint callable from JavaScript — no routes, no fetch, no boilerplate.

Backend (src/app.nim):

import jazzy_desktop

# This function becomes directly callable from JavaScript.
proc greet(name: string, age: int): string {.expose.} =
  return "Hello " & name & "! You are " & $age & " years old."

# Pass `ctx: Context` to access DB, headers, sessions.
# The macro knows not to expect `ctx` from the JS payload.
proc saveSettings(ctx: Context, theme: string): bool {.expose.} =
  storeSet("theme", %theme)
  return true

startDesktopApp(
  title   = "My Awesome App",
  width   = 1200,
  height  = 800,
  devUrl  = "http://localhost:5173",
  prodDir = "../frontend/dist"
)

Frontend (frontend/src/App.jsx):

import { jazzy } from './jazzy';

// Calling Nim feels exactly like calling a local async function.
const message = await jazzy.greet("Caner", 25);
// → "Hello Caner! You are 25 years old."

await jazzy.saveSettings("dark-mode");

Two-Way Events — Pushing Data from Nim to the Frontend

Emit real-time data from a background Nim thread directly to your React components via the built-in WebSocket event bus.

Nim side:

import jazzy_desktop/events

proc runHeavyTask() {.expose.} =
  for i in 1..100:
    emit("progress", %*{"value": i})
    sleep(50)

JavaScript side:

import { jazzy } from './jazzy';

// Subscribe on component mount
jazzy.on("progress", (data) => {
  setProgress(data.value);
});

// Clean up on unmount
jazzy.off("progress");

Native OS APIs

All native capabilities are exposed to your JavaScript frontend via the window-level bridge injected by Jazzy's WebView layer.

💻 Window Management

jazzyWindowMinimize();  // Minimize to taskbar
jazzyWindowMaximize();  // Maximize window
jazzyWindowRestore();   // Restore from maximized state
jazzyWindowHide();      // Hide window and taskbar entry
jazzyWindowShow();      // Bring back to foreground
jazzyWindowCenter();    // Center on the current monitor

Build fully frameless windows with native drag support and Windows 11 Mica backdrop blur effect — no additional configuration required.

📂 Native File Dialogs

import jazzy_desktop/dialogs

# Open dialog — pick an existing file
let file = selectFileDialog(
  "Choose an Image",
  @[DialogFilter(name: "Images", extensions: "*.png;*.jpg;*.webp")],
  multiSelect = false,
  forSave     = false
)

# Save dialog — choose where to write a new file
let dest = selectFileDialog(
  "Save Export",
  @[DialogFilter(name: "PDF", extensions: "*.pdf")],
  multiSelect = false,
  forSave     = true
)

Supports open dialogs, save dialogs, folder pickers, and native OS message boxes.

🔔 System Tray

Add your app to the system tray notification area (bottom-right corner on Windows) with a fully native right-click context menu, driven from jazzy_desktop/tray.

📋 Clipboard & Browser

import jazzy_desktop/clipboard
import jazzy_desktop/browser

writeClipboard("Copied from Nim!")
let text = readClipboard()

# Open in the user's default browser, not inside the WebView
openBrowser("https://nim-lang.org")

🔒 Single Instance Lock

enforceSingleInstance()
# Prevents duplicate app launches.
# Focuses the existing window instead of opening a second one.

Web Mode

Jazzy Desktop is built on top of the Jazzy Framework — a fast, production-ready Nim web framework. When you build a Jazzy Desktop app, a local Jazzy HTTP server runs in the background, serving your RPC endpoints, handling WebSocket events, and powering the optional ORM layer.

This means your app can be deployed as a standard web application with a single CLI flag — without touching your application code.

# Develop in the browser (no native window opened)
jazzyd dev --web

# Build a standalone web server binary for deployment
jazzyd build --web

The resulting binary can run on a Linux VPS, listen on port 8080, and serve behind Nginx like any conventional web app. Your desktop UI and business logic are shared 100% between both targets.

Project Structure

my-app/
├── frontend/               # Vite-powered frontend (React / Vue / Svelte)
│   ├── src/
│   │   ├── App.jsx
│   │   └── jazzy.js        # RPC client (JS Proxy, auto-generated)
│   └── vite.config.ts
│
├── src/
│   └── app.nim             # Entry point — expose procs, start the app
│
└── my-app.nimble

Configuration

startDesktopApp(
  title           = "My App",
  width           = 1200,
  height          = 800,
  devUrl          = "http://localhost:5173",
  prodDir         = "../frontend/dist",
  port            = 7654,   # Internal HTTP server port (default: 7654)
  maxUploadSizeMb = 50      # File upload limit in MB (default: 10)
)

Roadmap

Contributing

Jazzy Desktop is a young project and there is meaningful work ahead. Contributions are very welcome — especially around macOS support, new native APIs, and async macro improvements. Check the roadmap above for good first-contribution candidates.

_{Powered by Jazzy Framework ·
Built with ❤️ and Nim ·
MIT License}