Bundlers

A modern app is written as hundreds of small modules plus packages from npm. A bundler follows every import from an entry file, combines what is needed, removes unused code (tree shaking), minifies it and splits it into chunks that load on demand. It also handles CSS, images and TypeScript along the way.

webpack defined the category and is still found in many older projects. Newer tools written in faster languages have taken over most new work: esbuild (Go), Rolldown (a Rust bundler compatible with Rollup, which now powers Vite), Turbopack (Next.js) and Rspack, a webpack-compatible bundler in Rust. Most developers meet a bundler through a framework or Vite rather than configuring one by hand.