Rouille - Hello World in text/plain

web Rouille start_server router! GET text 404 Not Found empty_404

Part of the series about the Rouille micro-web framework in Rust.

Create a new crate

cargo new hello-world-text
cd hello-world-text


Add Rouille as a dependency to the Cargo.toml file:


name = "hello-world-text"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at

rouille = "3.6"

The code


extern crate rouille;

fn main() {
    let host = "localhost";
    let port = "8000";

    println!("Now listening on {host}:{port}");

    rouille::start_server(format!("{host}:{port}"), move |request| {
            (GET) (/) => {
                rouille::Response::text("Hello <b>world!</b>")
            _ => rouille::Response::empty_404()

  • We call rouille::start_server providing it the hostname and port number. Giving "localhost" or "" will ensure that the web server won't be accessible from outside of your computer. This is a good idea during development.

  • The router! macro helps us define the routes.

  • (GET) (/) => {} is the mapping that say what to do when an HTTP GET request arrives to the root (/) path on the server.

  • The rouille::Response::text method send a response setting the Content-Type to text/plain.

  • We also have a default route-handle: _ => rouille::Response::empty_404() calling the empty_404 method.

Running the code

cargo run

Will print Now listening on localhost:8000 on the console and we can visit http://localhost:8000/ with our browser and see

Hello <b>world!</b>

We won't see the text in bold, we'll see the HTML tag.

On Linux and probably also on macOs we can use another terminal to run the following command.

curl -i http://localhost:8000/

The -i flag of curl will make it show the header along the content.

HTTP/1.1 200 OK
Server: tiny-http (Rust)
Date: Mon, 01 Jan 2024 12:40:58 GMT
Content-Type: text/plain; charset=utf-8
Content-Length: 11

Hello <b>world!</b>

Here we can see clearly the Content-Type being text/plain. That's the reason the browser shows us the text and does not try to interpret it as HTML.

404 Not found

If we visit any other URL (e.g. http://localhost:8000/qqrq ) we'll get a blank page.

With curl we can verify that the HTTP response code was 404 as expected.

$ curl -i http://localhost:8000/qqrq
HTTP/1.1 404 Not Found
Server: tiny-http (Rust)
Date: Mon, 01 Jan 2024 12:45:42 GMT
Content-Length: 0

Related Pages

Rouille a web micro-framework in Rust


Gabor Szabo (szabgab)

Gabor Szabo, the author of the Rust Maven web site maintains several Open source projects in Rust and while he still feels he has tons of new things to learn about Rust he already offers training courses in Rust and still teaches Python, Perl, git, GitHub, GitLab, CI, and testing.

Gabor Szabo