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Wasmer Go

Build Status License Go Package API Documentation

Website • Docs • Slack Channel

A complete and mature WebAssembly runtime for Go based on Wasmer.


  • Easy to use: The wasmer API mimics the standard WebAssembly API,
  • Fast: wasmer executes the WebAssembly modules as fast as possible, close to native speed,
  • Safe: All calls to WebAssembly will be fast, but more importantly, completely safe and sandboxed.

Documentation: browse the detailed API documentation full of examples.

Examples as tutorials: browse the examples/ directory, it's the best place for a complete introduction!


To install the library, follow the classical:

$ go get

And you're ready to get fun!

Supported platforms

This library embeds the Wasmer runtime compiled as shared library objects, and so uses cgo to consume it. A set of precompiled shared library objects are provided. Thus this library works (and is tested) on the following platforms:

Platform Architecture Triple Status
Linux amd64 x86_64-unknown-linux-gnu ✅
aarch64 aarch64-unknown-linux-gnu ✅
Darwin amd64 x86_64-apple-darwin ✅
aarch64 aarch64-apple-darwin ⏳
Windows amd64 x86_64-pc-windows-msvc ⏳
What to do if your platform is missing?

Up to now, there is no script to automate that process. We are working on it.

Here are the steps to do that manually:

$ # Build the new Wasmer C API shared object library.
$ cargo build --release
$ # Configure cgo.
$ export CGO_CFLAGS="-I$(pwd)/wasmer/packaged/include/"
$ export CGO_LDFLAGS="-Wl,-rpath,$(pwd)/target/release/ -L$(pwd)/target/release/ -lwasmer_go"
$ # Run the tests.
$ just test -tags custom_wasmer_runtime


We highly recommend to read the examples/ directory, which contains a sequence of examples/tutorials. It's the best place to learn by reading examples.

But for the most eager of you, there is a quick toy program in examples/appendices/simple.go, written in Rust:

pub extern "C" fn sum(x: i32, y: i32) -> i32 {
    x + y

After compilation to WebAssembly, the examples/appendices/simple.wasm binary is generated.

Then, we can execute it in Go:

package main

import (
	wasmer ""

func main() {
    wasmBytes, _ := ioutil.ReadFile("simple.wasm")

    engine := wasmer.NewEngine()
    store := wasmer.NewStore(engine)

    // Compiles the module
    module, _ := wasmer.NewModule(store, wasmBytes)

    // Instantiates the module
    importObject := wasmer.NewImportObject()
    instance, _ := wasmer.NewInstance(module, importObject)

    // Gets the `sum` exported function from the WebAssembly instance.
    sum, _ := instance.Exports.GetFunction("sum")

    // Calls that exported function with Go standard values. The WebAssembly
    // types are inferred and values are casted automatically.
    result, _ := sum(5, 37)

    fmt.Println(result) // 42!

And then, finally, enjoy by running:

$ go run examples/appendices/simple.go


Run the tests with the following command:

$ just test

What is WebAssembly?

Quoting the WebAssembly site:

WebAssembly (abbreviated Wasm) is a binary instruction format for a stack-based virtual machine. Wasm is designed as a portable target for compilation of high-level languages like C/C++/Rust, enabling deployment on the web for client and server applications.

About speed:

WebAssembly aims to execute at native speed by taking advantage of common hardware capabilities available on a wide range of platforms.

About safety:

WebAssembly describes a memory-safe, sandboxed execution environment […].


The entire project is under the MIT License. Please read the LICENSE file.