Qz.jsEmbeddable WinterTC Runtime

Strict C99 · Low overhead · WinterTC standard runtime

Get Started

JS API

🔌

Message-based host boundary

Host and runtime exchange JSON over `qz_post_message` / `message_cb`. Inbound is thread-safe; outbound fires on the runtime thread. No `eval`, no `tick`.

🪶

Low overhead

~2.45 MiB stripped, <5 ms startup — fits embedded and edge targets where Node/bun can't.

📦

Zero system dependencies

The runtime and all its dependencies build from source via CMake. About 2.45 MiB stripped in the minimal profile.

⚡

Strict C99

Builds as C99 alongside its dependencies. Release `qzjs -e 'console.log(1)'` starts in under 5 ms; peak RSS stays near 3 MB.

🌐

WinterTC-compatible runtime

21 modules — fetch, crypto.subtle, streams, WebSocket, BroadcastChannel, EventSource, timers, fs, serve() and more. Precompiled to bytecode, available as globals.

🔒

No global state

Per-runtime isolation through an opaque `qz_t`. Multiple independent instances run in one process.

Quick Start

bash

# Clone with all submodules
git clone --recursive https://github.com/adam-ikari/qzjs.git
cd qzjs

# Configure and build
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j$(nproc)

#include <qzjs/qzjs.h>
#include <stdio.h>

static void on_message(qz_t *rt, const char *json, size_t len, void *data) {
    (void)rt; (void)data;
    printf("received: %.*s\n", (int)len, json);
}

int main(void) {
    qz_config_t cfg = {0};
    cfg.initial_script = "postMessage({hello: 'world'});";
    cfg.message_cb = on_message;
    qz_t *rt = qz_create(&cfg);
    if (!rt) return 1;
    qz_post_message(rt, "{\"cmd\":\"echo\",\"data\":\"hi\"}", 26);
    qz_destroy(rt);
    return 0;
}