3 releases (stable)

2.0.0 Oct 29, 2021
1.0.2 Feb 6, 2021
0.0.0 Feb 6, 2021

#672 in WebAssembly

Download history 35/week @ 2023-10-31 31/week @ 2023-11-07 39/week @ 2023-11-14 41/week @ 2023-11-21 40/week @ 2023-11-28 31/week @ 2023-12-05 28/week @ 2023-12-12 32/week @ 2023-12-19 35/week @ 2023-12-26 21/week @ 2024-01-02 34/week @ 2024-01-09 32/week @ 2024-01-16 22/week @ 2024-01-23 20/week @ 2024-01-30 31/week @ 2024-02-06 56/week @ 2024-02-13

135 downloads per month
Used in 11 crates (9 directly)

MIT license

33K SLoC

wasmer Build Status Join Wasmer Slack MIT License crates.io

Wasmer is the most popular WebAssembly runtime for Rust (...and also the fastest). It supports JIT (Just in Time) and AOT (Ahead of time) compilation as well as pluggable compilers suited to your needs.

It's designed to be safe and secure, and runnable in any kind of environment.


use wasmer::{Store, Module, Instance, Value, imports};

fn main() -> anyhow::Result<()> {
    let module_wat = r#"
    (type $t0 (func (param i32) (result i32)))
    (func $add_one (export "add_one") (type $t0) (param $p0 i32) (result i32)
        get_local $p0
        i32.const 1

    let store = Store::default();
    let module = Module::new(&store, &module_wat)?;
    // The module doesn't import anything, so we create an empty import object.
    let import_object = imports! {};
    let instance = Instance::new(&module, &import_object)?;

    let add_one = instance.exports.get_function("add_one")?;
    let result = add_one.call(&[Value::I32(42)])?;
    assert_eq!(result[0], Value::I32(43));



Wasmer is not only fast, but also designed to be highly customizable:

  • Pluggable Engines: do you have a fancy dlopen implementation? This is for you!
  • Pluggable Compilers: you want to emit code with DynASM or other compiler? We got you!
  • Headless mode: that means that no compilers will be required to run a serialized Module (via Module::deserialize()).
  • Cross-compilation: You can pre-compile a module and serialize it to then run it in other platform (via Module::serialize()).

Config flags

Wasmer has the following configuration flags:

  • wat (enabled by default): It allows to read WebAssembly files in their text format. This feature is normally used only in development environments
  • Compilers (mutually exclusive):
    • singlepass: it will use wasmer-compiler-singlepass as the default compiler (ideal for blockchains).
    • cranelift: it will use wasmer-compiler-cranelift as the default compiler (ideal for development).
    • llvm: it will use wasmer-compiler-llvm as the default compiler (ideal for production).

Wasmer ships by default with the cranelift compiler as its great for development proposes. However, we strongly encourage to use the llvm backend in production as it performs about 50% faster, achieving near-native speeds.

Note: if you want to use multiple compilers at the same time, it's also possible! You will need to import them directly via each of the compiler crates.

Made with ❤️ by the Wasmer team, for the community


~280K SLoC