Building from Source

Installing Rustup

Building Wasmer from source requires Rust 1.45+.

The easiest way to install Rust on your system is via Rustup. To get Rustup on Linux and macOS, you can run the following:

curl -sSf | sh

To install Rust on Windows, download and run rustup-init.exe, then follow the onscreen instructions.

Installing Additional Dependencies


Windows support is fully supported. WASI is fully supported, but Emscripten support is in the works.

  1. Install Visual Studio​

  2. Install Rust for Windows​

  3. Install Git for Windows. Allow it to add git.exe to your PATH(default settings for the installer are fine).

  4. (optional) Install LLVM 11.0​

Building the Wasmer Runtime

Wasmer is built with Cargo, the Rust package manager.

First, let's clone Wasmer:

git clone
cd wasmer

Wasmer supports three different compilers at the moment:

Singlepass Compiler

Build Wasmer:

make build-wasmer

Note: you should see this Enabled Compilers: singlepass in console.

You may disable Singlepass compiler with export ENABLE_SINGLEPASS=0.

Cranelift Compiler

The Cranelift compiler will work if you are in a X86 or ARM machine, so you don't need to do anything in your system to enable it.

make build-wasmer

Note: should see this as the first line in the console: Enabled Compilers: cranelift

You may disable Cranelift compiler with export ENABLE_CRANELIFT=0.

LLVM Compiler

If you want support for the Wasmer LLVM compiler, then you will also need to ensure:

  • Ensure that LLVM 10.0.x > is installed on your system

  • In case llvm-config is not accessible, set the correct environment variable for LLVM to access: For example, the environment variable for LLVM 11.0.x would be: LLVM_SYS_110_PREFIX=/path/to/unpacked/llvm-11.0

And create a Wasmer release

make build-wasmer

Note: you should see this in the console: Enabled Compilers: llvm

You may disable LLVM compiler with export ENABLE_LLVM=0.

All compilers

Once you have LLVM and Rust, you can just run:

make build-wasmer

Note: you should see this in the console: Enabled Compilers: singlepass cranelift llvm

Running your Wasmer binary

Once you run the make build-wasmer command, you will have a new binary ready to be used!

./target/release/wasmer quickjs.wasm

Building Wasmer C-API from source

Wasmer provides a pre-compiled version for the C-API on its release page.

However, you can also compile the shared library from source:

make build-capi

This will generate the shared library (depending on your system):

  • Windows: target/release/libwasmer_c_api.dll

  • macOS: target/release/libwasmer_c_api.dylib

  • Linux: target/release/

If you want to generate the library and headers for using them easily, you can execute:

make package-capi

This command will generate a package directory, that you can then use easily in the Wasmer C API examples.


By default, the Wasmer C API shared library will include all the compilers and engines available in the system where is built. Defaulting to cranelift and the universal engine if available.

You can generate the C-API for a specific compiler and engine with:

  • Singlepass:

    • Universal: make build-capi-singlepass-universal

    • Native Engine: not yet available ⚠ī¸

  • Cranelift:

    • Universal: make build-capi-cranelift-universal

    • Native Engine: make build-capi-cranelift-native

  • LLVM: make build-capi-llvm

    • Universal: make build-capi-llvm-universal

    • Native Engine: make build-capi-llvm-native