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. 1.
    Install Visual Studio
  2. 2.
    Install Rust for Windows
  3. 3.
    Install Git for Windows. Allow it to add git.exe to your PATH(default settings for the installer are fine).
  4. 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 ⚠️
  • 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