parcel-bundler/parcel

Parcel is a web application bundler, a tool that takes all the separate pieces of a web project (JavaScript files, CSS stylesheets, HTML pages, images, fonts, and so on) and packages them together into optimized files that browsers can efficiently load. The problem it was built to solve was that existing bundlers like webpack required hundreds of lines of configuration just to handle a typical project, and they were often painfully slow on large codebases. Parcel's defining feature is zero configuration. You point it at an entry file, usually your main HTML page, and it automatically traces all the dependencies, figures out what transformations each file needs (compiling modern JavaScript with Babel, processing CSS with PostCSS, transforming HTML with PostHTML), and bundles everything without you writing a single config file or installing extra plugins for common formats. Internally, Parcel builds a tree of assets from your entry point, processes each file using the appropriate handler, and then groups related assets into bundles. It handles code splitting automatically: if you use a dynamic import statement in JavaScript (a way of loading a chunk of code only when it's actually needed), Parcel creates a separate bundle for it. When an asset like a CSS file is imported from within JavaScript, Parcel places it in its own bundle rather than awkwardly inlining it. Speed comes from two sources: worker processes that compile files in parallel across all CPU cores, and a filesystem cache that saves compiled results so subsequent restarts are much faster. On a 1,700-module project, Parcel completed the build in roughly 10 seconds compared to webpack's 21 seconds, and just 2.6 seconds with cache warm. Parcel also includes a built-in development server with hot module replacement, meaning file changes appear instantly in the browser without a full page reload. The tool runs on Node.js and is installed as an npm or Yarn package. It works with JavaScript (CommonJS and ES6 modules), CSS, HTML, and generic file assets out of the box.