Set up Rust for FastEdge

The Modern Rust SDK is the recommended approach for new FastEdge HTTP applications. It is based on WASI-HTTP, the standard WebAssembly interface for HTTP applications, and uses the wstd crate, which provides Rust bindings for WASI-HTTP. Rust and Cargo are required. On Windows, also install Visual Studio Build Tools with the Desktop development with C++ workload.

Existing apps built with the fastedge crate and wasm32-wasip1 use a different setup — covered in the Legacy Rust guide.

Add the WebAssembly target

FastEdge runs applications compiled to wasm32-wasip2. Add the target once — it applies to all future builds:

rustup target add wasm32-wasip2

Configure a project

FastEdge applications compile to WebAssembly libraries rather than standalone executables, so start with a Rust library project. Two changes from the defaults are needed: the output type must be cdylib (a format the WASI runtime can load), and wstd must be listed as a dependency.

Create the library crate:
cargo new --lib my-app cd my-app

Replace the contents of Cargo.toml:

[package]
name = "my_app"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["cdylib"]

[dependencies]
wstd = "0.6"
anyhow = "1"

Without crate-type = ["cdylib"], the build succeeds but the output can’t run as a FastEdge application.

Verify the toolchain

A minimal handler is enough to confirm the toolchain produces a valid WebAssembly component. Replace src/lib.rs:

use wstd::http::body::Body;
use wstd::http::{Request, Response};

#[wstd::http_server]
async fn main(_request: Request<Body>) -> anyhow::Result<Response<Body>> {
    Ok(Response::builder()
        .status(200)
        .body(Body::from("OK"))?)
}

Build it:

cargo build --release --target wasm32-wasip2

The first build downloads dependencies and takes one to two minutes. When it completes without errors, the toolchain is ready — the compiled binary is at ./target/wasm32-wasip2/release/my_app.wasm.

Overview Rust (Legacy HTTP)

⌘I

​Add the WebAssembly target

​Configure a project

​Verify the toolchain

Add the WebAssembly target

Configure a project

Verify the toolchain