Build tools like Webpack, Vite, and Parcel automate the process of transforming, bundling, and optimizing frontend code assets — JavaScript modules, CSS, images, and fonts — for efficient delivery to browsers. They handle tasks like transpiling modern JavaScript (via Babel), minification, code splitting, and tree shaking (removing unused code). Build pipelines are standard in modern JavaScript development workflows and produce the optimized, minified code that ships in production websites.