Rollup

Rollup is an open source JavaScript module bundler. It compiles small pieces of code into a larger output and is widely used for libraries.

Rollup follows the import statements in your code and combines the modules into one bundle. It removes code that is never used through tree shaking, which keeps the output small. It can produce ES modules, CommonJS, UMD and SystemJS formats, and it supports code splitting when you use dynamic imports.

• Output in ES, CommonJS, UMD and SystemJS formats
• Tree shaking to remove unused code
• Code splitting with dynamic imports
• Plugin API for transforms and custom loading
• Many configuration options for special build flows

Library authors who publish packages for several module systems, and developers who want a bundler with a small, readable output. Teams with unusual build requirements will also find its options useful.

Rollup is free and released under the MIT license. Its configuration is more manual than that of zero-config tools, so expect to write a config file for most projects. Common needs are covered by existing plugins, and the plugin API is documented for writing your own.