Cosmopolitan WebView

one binary. every os. native GUI — from C, zero headers.

A tiny cross-platform webview library that compiles with cosmocc into a single portable APE (Actually Portable Executable).

It opens a native OS window with a WebKit/WebView2 webview — no dependencies, no package managers, no install. One binary, every OS.

// A complete hello-world webview app:
#include "webview_shim.h"

int main(void) {
    webview_shim_t w = {0};
    w.app_name = "Hello";
    w.html     = "<h1>hello world</h1>";

    if (webview_shim_init(&w) != 0) return 1;
    while (webview_shim_loop(&w, 1) == 0) {}
    webview_shim_exit(&w);
    return 0;
}

./build.sh               →  webview_demo  (768 KB APE)
./webview_demo           →  native window with your HTML

Features

• dlopen/dlsym at runtime — no system headers, no linker flags. ZERO includes.
• Portable APE — the same binary runs on macOS, Linux, and Windows (WebView2).
• JS↔C bridge — window.external.invoke(json) intercepted via WKNavigationDelegate (macOS), NavigationStarting (Windows), or WebKit user content manager (Linux). Handled via on_invoke.
• C→JS eval — call webview_shim_eval(w, "js code") to inject JavaScript.
• No malloc-churn — one allocation, one thread, no callbacks after init.

Quick start

git clone https://github.com/yourname/cosmo_webview.git
cd cosmo_webview
./build.sh
./webview_demo          # a window opens with a cute UI

API

Function	Description
webview_shim_init(w)	Create the native window + webview
webview_shim_loop(w, blocking)	Process one event loop frame
webview_shim_eval(w, js)	Execute JavaScript in the webview
webview_shim_exit(w)	Tear down everything

Structure

File	Role
webview_shim.h	Public C API (zero dependencies)
webview_shim.c	Platform dispatch + macOS / Linux / Windows backends
main.c	Demo app — shows what a real app looks like
build.sh / build.bat	Download cosmocc and compile the APE