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
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On this page
Installing Rustup
Installing Additional Dependencies
Building the Wasmer Runtime
Singlepass Compiler
Cranelift Compiler
LLVM Compiler
All compilers
Running your Wasmer binary
Building Wasmer C-API from source