Preact
Preact is a fast, lightweight JavaScript library for building user interfaces, designed as a drop-in alternative to React. It offers a similar API and component model to React but with a much smaller bundle size (around 3-4 kB gzipped) and optimized performance. It is often used in performance-critical web applications where minimizing JavaScript payload is a priority.
Developers should learn Preact when they need React-like functionality but with better performance and smaller bundle sizes, such as in progressive web apps, mobile-first sites, or projects with strict performance budgets. It is particularly useful for applications where fast initial load times and smooth interactions are crucial, as its lightweight nature reduces JavaScript parsing and execution overhead.