Build Modern UI, Your Way

Ilha is a lightweight, open-source web UI library designed around the island architecture pattern. It enables developers to build modern user interfaces by rendering plain HTML on the server and hydrating interactive components on the client without flicker. The core library is under 2,500 lines of code and has zero dependencies, making it small enough to be included in an AI prompt or pasted directly into projects. Ilha is TypeScript-first, requires no virtual DOM, and runs from a single import without the need for a complex toolchain or build transforms.

The library offers a familiar syntax for defining UI components, combining state, validation, events, and markup within self-contained islands. Its reactivity model draws inspiration from Svelte and React, using signals to enable fine-grained updates and signal-driven UI changes. Ilha avoids an app-wide re-render loop, focusing updates only on the data actually used by the UI. Developers can choose the appropriate rendering strategy for each island: static HTML for instant first paint, server-rendered hydration for interactive elements, or client-only rendering when SEO is not required.

Ilha provides useful extras such as routing, typed forms, and shared state management, which can be added as needed. File-based routing and dynamic page support are available via the @ilha/router package, while Zustand-shaped stores enable shared cart and session state across islands. The library is compatible with a wide range of backend technologies, including TypeScript, PHP, Ruby, Elixir, Rust, and Go, allowing it to fit into diverse application stacks.

The platform is fully open-source, with every line of code freely available and no paywalls or hidden tiers. Developers can start new projects quickly by choosing from templates and using the giget command, or experiment directly in an online sandbox. Ilha is positioned as a versatile solution for building modern web interfaces without the overhead or ceremony of traditional frameworks.