leptos-rs/leptos

Leptos is a web framework for building user-interface-heavy web applications, written in Rust. It is described as full-stack and isomorphic, meaning the same Rust code can run both in the browser and on the server. In the browser, the app is compiled to WebAssembly (a low-level format browsers can run natively) so it runs at near-native speed; on the server, the same components produce HTML that is sent to the browser and then hydrated, turned back into a live, interactive page. The defining design choice is what the README calls fine-grained reactivity. Instead of re-rendering whole components or diffing a virtual DOM, Leptos tracks dependencies at the level of individual reactive signals. When a signal changes, only the exact piece of DOM that depends on it, a single text node, a class toggle, an element added or removed, actually updates. The pitch is that this avoids virtual-DOM overhead and keeps the runtime small and fast. Apps are written declaratively. The code example shows a counter built with a view! macro that uses a JSX-like syntax inside Rust, plus an alternative builder syntax. The framework also exposes server functions, functions you can call from client-side code that only execute on the server, so database calls or authentication can live alongside the components that consume them without writing a separate REST API. A router is included. Recommended setup is cargo-leptos, a build tool that compiles both halves of the app together, plus starter templates for the Actix and Axum web servers. The dev server runs on localhost port 3000. The name Leptos is ancient Greek for thin or fine-grained. The full README is longer than what was provided.