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Used in 15 crates (14 directly)

MIT license

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This project was initialized from xray

A minimal library for building compiled Node.js add-ons in Rust.


Prisma     swc     Parcel   next.js   nextjs.svg

Platform Support

Lint Linux musl macOS/Windows/Linux x64 Linux-aarch64 Linux-armv7 macOS-Android Android-armv7 Windows i686 Windows arm64 FreeBSD


Rust 1.57.0

node12 node14 node16 node18
Windows x64
Windows x86
Windows arm64
macOS x64
macOS aarch64
Linux x64 gnu
Linux x64 musl
Linux aarch64 gnu
Linux aarch64 musl
Linux arm gnueabihf
Linux aarch64 android
Linux armv7 android
FreeBSD x64

This library depends on Node-API and requires Node@10.0.0 or later.

We already have some packages written by napi-rs: node-rs

One nice feature is that this crate allows you to build add-ons purely with the Rust/JavaScript toolchain and without involving node-gyp.


You can start from package-template to play with napi-rs

Define JavaScript functions

/// import the preludes
use napi::bindgen_prelude::*;
use napi_derive::napi;

/// module registration is done by the runtime, no need to explicitly do it now.
fn fibonacci(n: u32) -> u32 {
  match n {
    1 | 2 => 1,
    _ => fibonacci(n - 1) + fibonacci(n - 2),

/// use `Fn`, `FnMut` or `FnOnce` traits to defined JavaScript callbacks
/// the return type of callbacks can only be `Result`.
fn get_cwd<T: Fn(String) -> Result<()>>(callback: T) {

/// or, define the callback signature in where clause
fn test_callback<T>(callback: T)
where T: Fn(String) -> Result<()>

/// async fn, require `async` feature enabled.
/// [dependencies]
/// napi = {version="2", features=["async"]}
async fn read_file_async(path: String) -> Result<Buffer> {
    .map(|r| match r {
      Ok(content) => Ok(content.into()),
      Err(e) => Err(Error::new(
        format!("failed to read file, {}", e),

more examples at examples


This repository is a Cargo crate. Any napi-based add-on should contain Cargo.toml to make it a Cargo crate.

In your Cargo.toml you need to set the crate-type to "cdylib" so that cargo builds a C-style shared library that can be dynamically loaded by the Node executable. You'll also need to add this crate as a dependency.

name = "awesome"

crate-type = ["cdylib"]

napi = "2"
napi-derive = "2"

napi-build = "1"

And create build.rs in your own project:

// build.rs
extern crate napi_build;

fn main() {

So far, the napi build script has only been tested on macOS Linux Windows x64 MSVC and FreeBSD.

Install the @napi-rs/cli to help you build your Rust codes and copy Dynamic lib file to .node file in case you can require it in your program.

  "package": "awesome-package",
  "devDependencies": {
    "@napi-rs/cli": "^1.0.0"
  "napi": {
    "name": "jarvis" // <----------- Config the name of native addon, or the napi command will use the name of `Cargo.toml` for the binary file name.
  "scripts": {
    "build": "napi build --release",
    "build:debug": "napi build"

Then you can require your native binding:


The module_name would be your package name in your Cargo.toml.

xxx => ./xxx.node

xxx-yyy => ./xxx_yyy.node

You can also copy Dynamic lib file to an appointed location:

napi build [--release] ./dll
napi build [--release] ./artifacts

There are documents which contains more details about the @napi-rs/cli usage.


Because libraries that depend on this crate must be loaded into a Node executable in order to resolve symbols, all tests are written in JavaScript in the test_module subdirectory.

To run tests:

yarn build:test
yarn test

Features table

Rust Type Node Type NAPI Version Minimal Node version Enable by napi feature
u32 Number 1 v8.0.0
i32/i64 Number 1 v8.0.0
f64 Number 1 v8.0.0
bool Boolean 1 v8.0.0
String/&'a str String 1 v8.0.0
Latin1String String 1 v8.0.0 latin1
UTF16String String 1 v8.0.0
Object Object 1 v8.0.0
serde_json::Map Object 1 v8.0.0 serde-json
serde_json::Value any 1 v8.0.0 serde-json
Array Array 1 v8.0.0
Vec Array 1 v8.0.0
Buffer Buffer 1 v8.0.0
External External 1 v8.0.0
Null null 1 v8.0.0
Undefined/() undefined 1 v8.0.0
Result<()> Error 1 v8.0.0
T: Fn(...) -> Result Function 1 v8.0.0
Async/Future Promise 4 v10.6.0 async
AsyncTask Promise 1 v8.5.0
JsGlobal global 1 v8.0.0
JsSymbol Symbol 1 v8.0.0
Int8Array/Uint8Array ... TypedArray 1 v8.0.0
JsFunction threadsafe function 4 v10.6.0 napi4
BigInt BigInt 6 v10.7.0 napi6


~125K SLoC