Leptos — Build Fast Web Applications with Rust

What it is

Leptos is a full-stack Rust web framework that uses fine-grained reactivity inspired by SolidJS. It compiles to WebAssembly for the client side and runs server functions natively, giving you a single language for both frontend and backend.

Leptos targets Rust developers who want to build interactive web applications without switching to JavaScript. Its signals-based reactivity model updates only the DOM nodes that actually changed, avoiding the overhead of virtual DOM diffing.

The project is actively maintained and suitable for both individual developers and teams looking to integrate it into their existing toolchain. Documentation and community support are available for onboarding.

How it saves time or tokens

Leptos eliminates the need for separate frontend and backend codebases. Shared types between server and client prevent serialization mismatches. Fine-grained reactivity means smaller, faster updates compared to virtual DOM frameworks. WebAssembly compilation produces compact binaries that load quickly over slow connections.

For teams evaluating multiple tools in the same category, the clear documentation and active community reduce the time spent on research and troubleshooting. Getting started takes minutes rather than hours of configuration.

How to use

1. Install the Leptos CLI with cargo install cargo-leptos.
2. Create a new project with cargo leptos new my-app.
3. Define reactive components using signals (create_signal) and derived signals (create_memo).
4. Add server functions with the #[server] macro for database queries and API calls.
5. Run cargo leptos watch for development with hot reload.

Example

use leptos::*;

#[component]
fn Counter() -> impl IntoView {
    let (count, set_count) = create_signal(0);
    view! {
        <button on:click=move |_| set_count.update(|n| *n += 1)>
            "Count: " {count}
        </button>
    }
}

fn main() {
    mount_to_body(Counter)
}

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Common pitfalls

• Expecting Rust compile times to match JavaScript build times. Leptos projects take longer to compile, especially on first build. Use cargo leptos watch with incremental compilation.
• Trying to use JavaScript ecosystem libraries directly. WebAssembly interop exists but adds complexity. Prefer Rust-native solutions when available.
• Forgetting that signals are lazy. Derived signals only recompute when accessed, which can cause confusion if you expect eager evaluation.
• Not reading the changelog before upgrading. Breaking changes between versions can cause unexpected failures in production. Pin your version and review release notes.