Lepton

Desktop apps on the web engine your system already has. A Zig core, a Rust CLI, and no browser in the box.

$npm create lepton-app

No browser in the box.

Lepton doesn’t ship its own Chromium inside your app. It uses the web engine the operating system provides: WPE WebKit on Linux, and WebView2 on Windows in the beta. The rest is on the way, and we say which is which.

WPE WebKitLinuxworksThe engine Lepton uses today.
ServoLinuxexperimentalOptional, for those who’d rather avoid WebKit. Servo doesn’t cover the whole web yet, so it stays experimental. It is not in a release: --servo says so rather than building with WPE WebKit. Built in CI, it already serves a lepton:// page and carries the page’s calls to the core intact.
WebView2Windowsin the betaIn the 0.1.9 beta: apps build, run and package on Windows 10 and 11, without Microsoft’s loader. Chromium-based, but it comes with Windows; your app doesn’t carry it.

One event, three tracks.

Your page and the Zig core talk in binary frames over the app’s own scheme and shared memory. No JSON is parsed on the way. The core owns the window and asks the desktop for the rest.

A command is a Zig function.

Register it in main.zig, list it in lepton.config.json, call it from the page. A name the config doesn’t list is refused; a listed name with no command fails the build.

src-lepton/main.zig

pub const commands = core.webviewRegistry.checkedWith(
    AppState,
    &.{
        .{ .name = "app.name", .run = &appName },
    },
    core.webviewRegistry.pluginCommands(@import("lepton_plugins").all),
    core.webviewRegistry.permissionList(@import("build_options").permissions),
);

/// `app.name`: the product's name, as UTF-8.
fn appName(state: *AppState, _: []const u8, out: []u8) core.webviewRegistry.HandlerError!usize {
    if (state.product.len > out.len) return error.TooLarge;
    @memcpy(out[0..state.product.len], state.product);
    return state.product.len;
}

src/App.tsx

import { invoke } from "@lepton-desk/api/core";

const bytes = await invoke("app.name");
const name = new TextDecoder().decode(bytes);

lepton.config.json

{
  "productName": "hello-lepton",
  "renderPath": "webview",
  "permissions": ["app.name"]
}

One command to a running window.

This is the real output of lepton new, unedited. The CLI is a single native Rust binary; the npm package only launches it.

$ lepton new hello-lepton --template react-ts --target webview


  ◉ lepton  create an app · v0.1.9-beta.1

  ◆ Project     hello-lepton
  ◆ Frontend    React · TypeScript
  ◆ Render      webview · your page in WPE WebKit
  ◆ Plugins     none
  ◆ Identifier  hello-lepton

  ✔ Scaffolded the React · TypeScript frontend      6 files
  ✔ Added the Lepton core                           119 files
  ✔ Wired the window, commands and permissions      12 files

  Your app is ready in hello-lepton

    cd hello-lepton
    pnpm install            install the dependencies
    pnpm lepton dev         open the window, with hot reload
    pnpm lepton build       build a release binary

  docs  https://github.com/lepton-desk/lepton

$ lepton package


  ◉ lepton  package · v0.1.9-beta.1

  ▸ types          zig-0.16 build commands --release=safe -Doptimize=ReleaseSmall…
  ✔ types          10.7 s
  ◆ commands       src/lepton-commands.d.ts updated
  ▸ frontend       pnpm run build
  ✔ frontend       2.0 s
  ▸ core           zig-0.16 build --release=safe -Doptimize=ReleaseSmall -Dname=he…
  ✔ core           8.0 s
  ◆ built          src-lepton/zig-out/bin
  ◆ packaged       src-lepton/bundle/hello-lepton-0.1.0-linux-x86_64
  ◆ depends        glib2 glibc libsoup3 libxcb wayland wpewebkit
  ◆ tar.gz         src-lepton/bundle/hello-lepton-0.1.0-linux-x86_64.tar.gz  176601 bytes  sha256 2ef7df5ad2f1c47490a0dfcbd081ddc78702f50144f3fc4bad804c4e05ae8e97

176,601 bytes: the app itself. WebKit comes from the system.

Its memory while running is another matter: measured →

What works, and what doesn’t yet.

Lepton is early. This table is the honest version.

Item	State	Note
Linux (Wayland, X11)	works	Own windows, client-side title bar, its own systemd scope; the title follows document.title.
Templates	works	React, Vue, Svelte, Solid, vanilla in TypeScript, React and vanilla also in JavaScript; npm, pnpm, Yarn, Bun. New TypeScript projects pass tsc and biome check.
More templates	in the beta	Astro, Next.js, Angular, Preact and Lit, and JavaScript for every Vite template: 19 in all, each checked with biome, tsc, a package and a window. Any other framework runs with one frontend setting.
Web engine features	works	Inspector (F12) in debug builds, downloads, permission requests, notifications, links in the desktop’s browser.
Packages	works	.tar.gz, .deb and Arch, reproducible, with --verify.
Plugins	works	fs, dialog, clipboard, os.
Record and replay	works	lepton record / replay: a session’s calls to the core, run again with or without the window; a recording can be a test.
lepton update	works	Brings a project’s packages, core and src-lepton/ files to the new version and keeps your edits.
Native render path	works	Drawn by the core on the GPU with GLES 3, no web engine; shared memory without a GPU.
Windows	in the beta	WebView2 apps build, run and package as .zip and an MSI made without WiX. All four plugins were measured there. The native path runs too, drawn on the CPU with DirectWrite text; the GPU (D3D11) is next.
macOS	not supported	Signing and notarizing need a paid Apple account and Mac hardware; a single maintainer cannot keep that up.
Native UI with web tech	planned	React, HTML/CSS and JS drawn by Lepton itself, 0.2.0.
Vulkan rendering	planned	0.2.0. Its floor is measured on a Radeon R7 240: Vulkan 1.3.

Web engines use memory, and WebView RAM can be high. We know that, and we won’t pretend otherwise: on Windows the same template measured 69.4 MB as a web view app and 6.9 MB as a native one.

Try it on your machine.

Linux with WPE WebKit 2.54+, or Windows 10 or 11 in the beta; Node 20+ and Zig 0.16. lepton info tells you what is missing.

$npm create lepton-app

Getting started Star or watch on GitHub

LeptonLepton is a Lepton Desk project.MIT or Apache-2.0Türkçe GitHub