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Wasmer is a standalone JIT WebAssembly runtime, aiming to be fully compatible with WASI and Emscripten.

Install Wasmer with:

curl -sSfL | sh

Wasmer runtime can also be embedded in different languages, so you can use WebAssembly anywhere :


Wasmer can execute both the standard binary format (.wasm) and the text format defined by the WebAssembly reference interpreter (.wat).

Once installed, you will be able to run any WebAssembly files (including Lua, PHP, SQLite and nginx!):

# Run Lua
wasmer run examples/lua.wasm

# Run PHP
wasmer run examples/php.wasm

# Run SQLite
wasmer run examples/sqlite.wasm

# Run nginx
wasmer run examples/nginx/nginx.wasm -- -p examples/nginx -c nginx.conf

Code Structure

Wasmer is structured into different directories:

  • src: code related to the Wasmer executable itself
  • lib: modularized libraries that Wasmer uses under the hood
  • examples: some useful examples to getting started with Wasmer


Building Wasmer requires rustup.

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

To build on other systems, run:

curl -sSf | sh

Other dependencies

Please select your operating system:


If you have Homebrew installed:

brew install cmake

Or, in case you have MacPorts:

sudo port install cmake

Debian-based Linuxes

sudo apt install cmake


pkg install cmake

Windows (MSVC)

Windows support is highly experimental. Only simple Wasm programs may be run, and no syscalls are allowed. This means nginx and Lua do not work on Windows. See this issue regarding Emscripten syscall polyfills for Windows.

  1. Install Visual Studio

  2. Install Rust for Windows

  3. Install Python for Windows. The Windows x86-64 MSI installer is fine. Make sure to enable "Add python.exe to Path" during installation.

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

  5. Install CMake. Ensure CMake is in your PATH.

  6. Install LLVM 7.0


Wasmer is built with Cargo, the Rust package manager.

# checkout code
git clone
cd wasmer

# install tools
# make sure that `python` is accessible.
cargo install --path .


Thanks to spec tests we can ensure 100% compatibility with the WebAssembly spec test suite.

Tests can be run with:

make test

If you need to regenerate the Rust tests from the spec tests you can run:

make spectests

You can also run integration tests with:

make integration-tests


Benchmarks can be run with:

cargo bench --all


Wasmer is an open project guided by strong principles, aiming to be modular, flexible and fast. It is open to the community to help set its direction.

Below are some of the goals of this project (in order of priority):

  • It should be 100% compatible with the WebAssembly spec tests
  • It should be fast (partially achieved)
  • Support WASI (in the works)
  • Support Emscripten calls (in the works)
  • Support Rust ABI calls
  • Support Go ABI calls


If you would like to know how Wasmer works under the hood, please see


Wasmer is primarily distributed under the terms of the MIT license (LICENSE).


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