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bun-win32

Zero-dependency Win32 FFI bindings for Bun on Windows. Each system DLL is a standalone @bun-win32/* package with full type definitions.

Install

# Per-DLL packages:
bun add @bun-win32/kernel32 @bun-win32/user32 # etc...

# Or pull the entire surface in one install:
bun add @bun-win32/all     # scoped meta-package
bun add bun-win32          # unscoped alias for the same surface

Requires Bun >= 1.1.0 and Windows 10+.

Usage

After the first call resolves the symbol via dlopen/dlsym, the native function pointer is cached directly on the class. Every subsequent call is a straight pointer invocation through Bun's FFI - no marshaling layer, no runtime type checks, no wrapper overhead. It's the same codepath as calling the C function yourself.

For hot paths, Preload() resolves symbols eagerly so even the first call pays zero binding cost:

import Kernel32 from '@bun-win32/kernel32';

const pid = Kernel32.GetCurrentProcessId();
const ticks = Kernel32.GetTickCount64();

import User32 from '@bun-win32/user32';

User32.Preload(['GetForegroundWindow', 'SetWindowPos']);

const { GetForegroundWindow, SetWindowPos } = User32;

SetWindowPos(hWnd, 0n, x, y, width, height, flags);

[!IMPORTANT]

If you destructure before binding, you capture the lazy wrapper instead of the native function.

Packages

All type definitions are provided by @bun-win32/core.

Published packages are AI-friendly. Alongside the README.md, each package includes an AI.md file that documents the binding contract, type surface, and source layout so coding agents can use the package correctly.

Graphics & Windowing

Shortened. The full README is on GitHub.