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Official IRC channel: #winapi on Mozilla IRC

This crate provides raw FFI bindings to all of Windows API. They are gathered by hand using the Windows 10 SDK from Microsoft. I aim to replace all existing Windows FFI in other crates with this crate through the "Embrace, extend, and extinguish" technique.

If this crate is missing something you need, feel free to create an issue, open a pull request, or contact me via other means.

This crate depends on Rust 1.6 or newer on Windows. On other platforms this crate is a no-op and should compile with Rust 1.2 or newer.

Frequently asked questions

How do I create an instance of a union?

Use std::mem::zeroed() to create an instance of the union, and then assign the value you want using one of the variant methods.

Why am I getting errors about unresolved imports?

Each module is gated on a feature flag, so you must enable the appropriate feature to gain access to those items. For example, if you want to use something from winapi::um::winuser you must enable the winuser feature.

How do I know which module an item is defined in?

You can use the search functionality in the documentation to find where items are defined.

Why is there no documentation on how to use anything?

This crate is nothing more than raw bindings to Windows API. If you wish to know how to use the various functionality in Windows API, you can look up the various items on MSDN which is full of detailed documentation.

Can I use this library in no_std projects?

Yes, absolutely! By default the std feature of winapi is disabled, allowing you to write Windows applications using nothing but core and winapi.

Why is winapi's HANDLE incompatible with std's HANDLE?

Because winapi does not depend on std by default, it has to define c_void itself instead of using std::os::raw::c_void. However, if you enable the std feature of winapi then it will re-export c_void from std and cause winapi's HANDLE to be the same type as std's HANDLE.

Should I still use those -sys crates such as kernel32-sys?

No. Those crates are a legacy of how winapi 0.2 was organized. Starting with winapi 0.3 all definitions are directly in winapi itself, and so there is no longer any need to use those -sys crates.



winapi = { version = "0.3", features = ["winuser"] }

#[cfg(windows)] extern crate winapi;
use std::io::Error;

fn print_message(msg: &str) -> Result<i32, Error> {
    use std::ffi::OsStr;
    use std::iter::once;
    use std::os::windows::ffi::OsStrExt;
    use std::ptr::null_mut;
    use winapi::um::winuser::{MB_OK, MessageBoxW};
    let wide: Vec<u16> = OsStr::new(msg).encode_wide().chain(once(0)).collect();
    let ret = unsafe {
        MessageBoxW(null_mut(), wide.as_ptr(), wide.as_ptr(), MB_OK)
    if ret == 0 { Err(Error::last_os_error()) }
    else { Ok(ret) }
fn print_message(msg: &str) -> Result<(), Error> {
    println!("{}", msg);
fn main() {
    print_message("Hello, world!").unwrap();

Financial Support

Do you use winapi in your projects? If so, you may be interested in financially supporting me on Patreon. Companies in particular are especially encouraged to donate (I'm looking at you Microsoft).