What is code splitting and how does it improve performance?

Code splitting divides JavaScript bundles into smaller chunks that load only when needed, rather than loading all code upfront. This improves initial load time by reducing the amount of JavaScript that must be downloaded and parsed before the page becomes interactive. Code splitting can be done by route (load code for each page separately), by component (load components on demand), or by feature (load features when needed). Modern frameworks like React and Next.js support code splitting out of the box. Example: A single-page app reduced initial bundle size from 500KB to 150KB by splitting code by route, improving Time to Interactive from 4 seconds to 1.5 seconds.