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Alex Spinov
Alex Spinov

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Leptos Has a Free Framework: Build Full-Stack Web Apps in Rust With Fine-Grained Reactivity and Zero Virtual DOM

#rust #webdev #opensource #tutorial

You write Rust for backends because you love the type safety and performance. But your frontend is still React — a separate language, separate toolchain, separate mental model. What if your entire web app — server, client, routing, data fetching — was one Rust codebase with compile-time guarantees? That's Leptos.

What Leptos Actually Does

Leptos is a full-stack Rust web framework with fine-grained reactivity. Unlike React's virtual DOM diffing, Leptos tracks exactly which DOM nodes depend on which signals. When data changes, only the affected text node or attribute updates — no tree diffing, no reconciliation.

Leptos compiles to WebAssembly for the client and native code for the server. Server functions let you write backend logic inline with your components — the framework handles the RPC boundary. The result: a full-stack web app in one language with type-safe API calls between client and server.

Leptos supports SSR, SSG, hydration, streaming HTML, and islands architecture. Open-source under MIT license.

Quick Start 

cargo install cargo-leptos
cargo leptos new --git https://github.com/leptos-rs/start
cd your-project
cargo leptos watch
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A basic counter component:

use leptos::*;

#[component]
fn Counter() -> impl IntoView {
    let (count, set_count) = signal(0);

    view! {
        <button on:click=move |_| set_count.update(|n| *n += 1)>
            "Count: " {count}
        </button>
    }
}
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Server function with type-safe client-server communication:

#[server(GetPosts)]
async fn get_posts(category: String) -> Result<Vec<Post>, ServerFnError> {
    // This runs on the server — direct DB access
    let posts = sqlx::query_as!(Post,
        "SELECT * FROM posts WHERE category = $1", category
    ).fetch_all(&pool()).await?;
    Ok(posts)
}

#[component]
fn PostList() -> impl IntoView {
    let posts = Resource::new(
        || "tech".to_string(),
        |category| get_posts(category)
    );

    view! {
        <Suspense fallback=|| view! { <p>"Loading..."</p> }>
            {move || posts.get().map(|data| data.unwrap().iter().map(|post|
                view! { <article><h2>{&post.title}</h2></article> }
            ).collect_view())}
        </Suspense>
    }
}
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3 Practical Use Cases

1. Real-Time Dashboard 

#[component]
fn MetricsDashboard() -> impl IntoView {
    let (metrics, set_metrics) = signal(Metrics::default());

    // SSE stream from server
    let _ = create_effect(move |_| {
        spawn_local(async move {
            let mut stream = get_metrics_stream().await;
            while let Some(m) = stream.next().await {
                set_metrics.set(m);
            }
        });
    });

    view! {
        <div class="dashboard">
            <Metric label="CPU" value=move || metrics().cpu />
            <Metric label="Memory" value=move || metrics().memory />
            <Metric label="Requests/s" value=move || metrics().rps />
        </div>
    }
}
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Fine-grained reactivity means only the changed metric value re-renders.

2. Form Handling with Validation 

#[server(CreateUser)]
async fn create_user(name: String, email: String) -> Result<User, ServerFnError> {
    if !email.contains('@') {
        return Err(ServerFnError::new("Invalid email"));
    }
    db::create_user(&name, &email).await
}

#[component]
fn SignupForm() -> impl IntoView {
    let action = ServerAction::<CreateUser>::new();

    view! {
        <ActionForm action=action>
            <input type="text" name="name" placeholder="Name" />
            <input type="email" name="email" placeholder="Email" />
            <button type="submit">"Sign Up"</button>
        </ActionForm>
    }
}
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3. Static Site Generation 

#[component]
fn BlogPost(slug: String) -> impl IntoView {
    let post = Resource::new(move || slug.clone(), load_post);
    // Pre-rendered at build time, hydrated on client
    view! { <article inner_html=move || post.get().map(|p| p.html) /> }
}
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Why This Matters

Leptos proves that Rust on the web isn't a compromise — it's an upgrade. Type safety from database to DOM. No JavaScript build toolchain. Compile-time guarantees that eliminate entire classes of bugs. And performance that WebAssembly delivers by default.

For teams already using Rust on the backend, Leptos eliminates the context switch between languages. One codebase, one type system, one compiler catching your mistakes.

Need custom data extraction or web scraping solutions? I build production-grade scrapers and data pipelines. Check out my Apify actors or email me at spinov001@gmail.com for custom projects.

Follow me for more free API discoveries every week!

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