How to use middleware in Axum

Use Router::layer to apply middleware to all routes or route_layer to apply it to specific routes.

use axum::{routing::get, Router};

#[tokio::main]
async fn main() {
    let app = Router::new()
        .route("/", get(|| async { "Hello" }))
        .layer(axum::middleware::from_fn(my_middleware));

    axum::serve(
        tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap(),
        app.into_make_service(),
    )
    .await
    .unwrap();
}

async fn my_middleware<B>(
    req: axum::extract::Request,
    next: axum::middleware::Next<B>,
) -> axum::response::Response {
    let res = next.run(req).await;
    res
}

Middleware acts like a filter that processes every request before it reaches your main code and every response before it leaves. You use it to handle common tasks like logging, authentication, or adding headers without repeating code in every function. Think of it as a security checkpoint that every visitor must pass through before entering the building.