Preact is a lightweight JavaScript framework that provides a fast alternative to React, packaged at 4kB in size. It delivers the full power of virtual DOM components and modern React-style APIs without the overhead associated with larger frameworks. The project is written in JavaScript and maintains a focus on performance optimization while preserving developer familiarity through React-compatible patterns.
The core functionality of Preact centers on component-based UI development using virtual DOM technology. Developers can write components as ES6 classes, functional components, or using React hooks, with support for JSX syntax or HTM as alternative markup approaches. The framework includes a highly optimized diff algorithm that minimizes DOM operations by calculating differences between component states and updating only what has changed. Preact also supports server-side rendering with seamless hydration, allowing applications to render on the server and continue interactively on the client.
Preact's compatibility layer, accessible via the preact/compat alias, provides extensive React compatibility, enabling developers to use existing React libraries and patterns with minimal friction. The framework includes comprehensive tooling support through DevTools integration, hot module replacement for development workflows, and transparent asynchronous rendering with a pluggable scheduler. All modern browsers are supported, and the framework works across isomorphic and custom element use cases.
The repository is currently in active development on the main branch, which represents an upcoming release, while the v10.x branch maintains patches for version 10.
The project's contributor base overlaps with major repositories including Microsoft's VSCode and TypeScript implementations, as well as the Rust language project, suggesting influence from and collaboration with significant open-source ecosystems.
The framework is positioned as a performance-focused, modular architecture for building user interfaces with functional programming patterns. It emphasizes efficiency through its minimal bundle size while maintaining the developer experience patterns that React users expect. The project maintains an ecosystem of related libraries documented in the awesome-preact list and receives backing from notable sponsors including Snyk, The Guardian, Deno, and various individual contributors through its OpenCollective funding model.
