Leptos is a full‑stack Rust framework for building web apps that supports client-only SPAs, SSR/MPR rendered on the server, and hydrated progressive apps. It offers fine‑grained reactivity, server functions, and cohesive front‑end/backend code using shared Rust abstractions.
egui is a portable, Rust-native immediate mode GUI library that runs natively and in browsers (compiled to WebAssembly). It emphasizes ease of use, simplicity, and portability—ideal for lightweight applications, tools, and embedding into game engines or Rust applications.