Rollup

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What Rollup is

Rollup is a free JavaScript module bundler for assembling smaller code pieces into applications or libraries. It can produce formats such as ES modules, CommonJS, UMD, AMD, IIFE, and SystemJS, for builds targeting browsers or Node.js. Its static analysis removes imported code a build does not use, and code splitting can distribute code across entry points and dynamic imports according to the output format’s import mechanism. Developers can configure inputs, outputs, plugins, tree-shaking, and watch mode. Rollup offers both a command-line interface and a JavaScript API, plus a plugin API for code transformations and injections. A plugin can also enable imports of existing CommonJS modules. The site includes a browser REPL for ES6 modules with several output format choices. It also notes that Vite pre-configures Rollup with defaults and plugins, and that WMR adopted its plugin API. Rollup is released under the MIT License. The project recommends using current versions of Rollup and its official plugins, and directs vulnerability reports to a private GitHub Security channel.

Who it suits

Rollup suits developers building JavaScript applications or libraries for browsers and Node.js who want configurable outputs, plugins, tree-shaking, and code splitting. Its browser REPL also offers a way to convert ES6 modules into selected formats.

What it does well

Free and released under the MIT License.
Supports multiple output formats, including ES modules and CommonJS.
Removes unused imported code through tree-shaking.
Offers CLI, JavaScript API, and plugin API.
Browser REPL accepts ES6 modules.

What to know first

Importing CommonJS modules requires a plugin.
Project recommends using the latest Rollup and official plugins.

Getting started

Visit https://rollupjs.org/
Use the command-line interface or JavaScript API
Configure inputs, outputs, plugins, tree-shaking, or watch mode
Try ES6 modules in the linked browser REPL

Verdict

Rollup offers configurable bundling for applications and libraries, with tree-shaking, code splitting, and several interfaces. Developers importing CommonJS modules need a plugin, and the project recommends keeping Rollup and official plugins current.

Questions

How much does Rollup cost?

Rollup is free, with a free plan and no free trial.

Which output formats can it produce?

Formats include ES modules, CommonJS, UMD, AMD, IIFE, and SystemJS.

Can Rollup import CommonJS modules?

Yes. Existing CommonJS modules can be imported through a plugin.

Can I use Rollup in a browser?

The site links to a browser REPL that accepts ES6 modules and provides output format choices.

What license does Rollup use?

Rollup is released under the MIT License.

How can I report a vulnerability?

The project asks reporters to submit a private vulnerability report through GitHub Security.

Facts from Rollup's own pages

Browser REPL: Rollup provides a browser REPL that accepts ES6 modules and offers output format choices including ES, AMD, CJS, IIFE, UMD, and System. · rollupjs.org, 4 Oct 2026
Browser use: The documentation includes a page for running Rollup in a browser, and the site links to an online REPL. · rollupjs.org, 4 Oct 2026
Code formats: Rollup can output formats including ES modules, CommonJS, UMD, AMD, IIFE, and SystemJS. · rollupjs.org, 4 Oct 2026
Code splitting: It can split code across entry points and dynamic imports using the output format’s import mechanism. · rollupjs.org, 4 Oct 2026
Compatibility: Rollup can import existing CommonJS modules through a plugin. · rollupjs.org, 4 Oct 2026
Configuration: Rollup provides configuration options for inputs, outputs, plugins, tree-shaking, and watch mode. · rollupjs.org, 4 Oct 2026
Integrations: The site says Vite pre-configures Rollup with defaults and plugins, and names WMR as a project that adopted its plugin API. · rollupjs.org, 4 Oct 2026
Interfaces: Rollup can be used from a command line interface or through its JavaScript API. · rollupjs.org, 4 Oct 2026
License: Rollup is released under the MIT License. · rollupjs.org, 4 Oct 2026
Output formats: It supports output formats including ES modules, CommonJS, UMD, and SystemJS. · rollupjs.org, 4 Oct 2026
Plugins: Rollup provides a plugin API for code injections and transformations. · rollupjs.org, 4 Oct 2026
Purpose: Rollup is a JavaScript module bundler that compiles small pieces of code into larger applications or libraries. · rollupjs.org, 4 Oct 2026
Security: The project asks users to report vulnerabilities through a private GitHub vulnerability report and recommends using the latest Rollup and official plugin versions. · github.com, 4 Oct 2026
Security guidance: The security page recommends using the latest versions of Rollup and its official plugins. · github.com, 4 Oct 2026
Security reporting: The project asks vulnerability reporters to submit a private vulnerability report through GitHub Security. · github.com, 4 Oct 2026
Support: The Rollup site links to a chat channel and to Open Collective for project contributions. · rollupjs.org, 4 Oct 2026
Tree-shaking: Rollup statically analyzes imported code and excludes parts that are not used. · rollupjs.org, 4 Oct 2026
Use cases: The project describes Rollup as suitable for building libraries and applications, including builds targeting browsers and Node.js. · rollupjs.org, 4 Oct 2026

Where Rollup stands on Freedom251

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