Installation

The Wasmtime CLI can be installed on Linux and macOS (locally) with a small install
script:

curl https://wasmtime.dev/install.sh -sSf | bash

This script installs into $WASMTIME_HOME (defaults to $HOME/.wasmtime), and executable is placed in $WASMTIME_HOME/bin.

After running the install script above, follow the on-screen instructions.

Windows or otherwise interested users can download installers and
binaries directly from the GitHub
Releases page.

For additional installation options, refer to the online book CLI installation page.

Documentation on Wasmtime's currently supported versions can be found in the
online book
documentation.

Example

If you've got the Rust compiler
installed then you can take some Rust
source code:

fn main() {
    println!("Hello, world!");
}

and compile it into a WebAssembly component with:

rustup target add wasm32-wasip2
rustc hello.rs --target wasm32-wasip2

Once compiled, you can run your component:

wasmtime hello.wasm

You should see the following output:

Hello, world!

(Note: make sure you installed Rust using the rustup method in the official
instructions above, and do not have a copy of the Rust toolchain installed on
your system in some other way as well (e.g. the system package manager). Otherwise, the rustup target add...
command may not install the target for the correct copy of Rust.)

Features

• Fast. Wasmtime is built on the optimizing Cranelift code generator to
  quickly generate high-quality machine code either at runtime or
  ahead-of-time. Wasmtime is optimized for efficient instantiation, low-overhead
  calls between the embedder and wasm, and scalability of concurrent instances.

• Secure. Wasmtime's development is strongly focused on correctness and
  security. Building on top of Rust's runtime safety guarantees, each Wasmtime
  feature goes through careful review and consideration via an RFC
  process. Once features are designed and implemented, they undergo 24/7
  fuzzing donated by Google's OSS Fuzz. As features stabilize they become part
  of a release, and when things go wrong we have a
  well-defined security policy in place to quickly mitigate and patch any
  issues. We follow best practices for defense-in-depth and integrate
  protections and mitigations for issues like Spectre. Finally, we're working to
  push the state-of-the-art by collaborating with academic researchers to
  formally verify critical parts of Wasmtime and Cranelift.

• Configurable. Wasmtime uses sensible defaults, but can also be
  configured to provide more fine-grained control over things like CPU and
  memory consumption. Whether you want to run Wasmtime in a tiny environment or
  on massive servers with many concurrent instances, we've got you covered.

• WASI. Wasmtime supports a rich set of APIs for interacting with the host
  environment through the WASI standard.

• Standards Compliant. Wasmtime passes the official WebAssembly test
  suite, implements the official C
  API of wasm, and implements
  future proposals to WebAssembly as
  well. Wasmtime developers are intimately engaged with the WebAssembly
  standards process all along the way too.

Language Support

You can use Wasmtime from a variety of different languages through embeddings of
the implementation.

Languages supported by the Bytecode Alliance:

• Rust - the wasmtime crate
• C - the wasm.h, wasi.h, and wasmtime.h headers, CMake
• C++ - the wasmtime.hh header
• Python - the wasmtime PyPI package
• .NET - the Wasmtime NuGet package
• Go - the wasmtime-go repository
• Ruby - the wasmtime gem

Languages supported by the community:

• Elixir - the wasmex hex package
• Perl - the Wasm Perl package's Wasm::Wasmtime

Documentation

📚 Read the Wasmtime guide here! 📚

The wasmtime guide is the best starting point to learn about what
Wasmtime can do for you or help answer your questions about Wasmtime. If you're
curious in contributing to Wasmtime, it can also help you do
that!

It's Wasmtime.