Next-generation ES module bundler

npm install rollup


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Rollup is a module bundler for JavaScript which compiles small pieces of code into something larger and more complex, such as a library or application. It uses the standardized ES module format for code, instead of previous idiosyncratic solutions such as CommonJS and AMD. ES modules let you freely and seamlessly combine the most useful individual functions from your favorite libraries. Rollup can optimize ES modules for faster native loading in modern browsers, or output a legacy module format allowing ES module workflows today.

Quick Start Guide

Install with npm install --global rollup. Rollup can be used either through a command line interface with an optional configuration file, or else through its JavaScript API. Run rollup --help to see the available options and parameters. The starter project templates, rollup-starter-lib and rollup-starter-app, demonstrate common configuration options, and more detailed instructions are available throughout the user guide.


These commands assume the entry point to your application is named main.js, and that you'd like all imports compiled into a single file named bundle.js.

For browsers:

# compile to a <script> containing a self-executing function
rollup main.js --format iife --name "myBundle" --file bundle.js

For Node.js:

# compile to a CommonJS module
rollup main.js --format cjs --file bundle.js

For both browsers and Node.js:

# UMD format requires a bundle name
rollup main.js --format umd --name "myBundle" --file bundle.js


Developing software is usually easier if you break your project into smaller separate pieces, since that often removes unexpected interactions and dramatically reduces the complexity of the problems you'll need to solve, and simply writing smaller projects in the first place isn't necessarily the answer. Unfortunately, JavaScript has not historically included this capability as a core feature in the language.

This finally changed with ES modules support in JavaScript, which provides a syntax for importing and exporting functions and data so they can be shared between separate scripts. Most browsers and Node.js support ES modules. However, Node.js releases before 12.17 support ES modules only behind the --experimental-modules flag, and older browsers like Internet Explorer do not support ES modules at all. Rollup allows you to write your code using ES modules, and run your application even in environments that do not support ES modules natively. For environments that support them, Rollup can output optimized ES modules; for environments that don't, Rollup can compile your code to other formats such as CommonJS modules, AMD modules, and IIFE-style scripts. This means that you get to write future-proof code, and you also get the tremendous benefits of...

Tree Shaking

In addition to enabling the use of ES modules, Rollup also statically analyzes and optimizes the code you are importing, and will exclude anything that isn't actually used. This allows you to build on top of existing tools and modules without adding extra dependencies or bloating the size of your project.

For example, with CommonJS, the entire tool or library must be imported.

// import the entire utils object with CommonJS
var utils = require('utils');
var query = 'Rollup';
// use the ajax method of the utils object
utils.ajax('https://api.example.com?search=' + query).then(handleResponse);

But with ES modules, instead of importing the whole utils object, we can just import the one ajax function we need:

// import the ajax function with an ES import statement
import { ajax } from 'utils';
var query = 'Rollup';
// call the ajax function
ajax('https://api.example.com?search=' + query).then(handleResponse);

Because Rollup includes the bare minimum, it results in lighter, faster, and less complicated libraries and applications. Since this approach is based on explicit import and export statements, it is vastly more effective than simply running an automated minifier to detect unused variables in the compiled output code.


Importing CommonJS

Rollup can import existing CommonJS modules through a plugin.

Publishing ES Modules

To make sure your ES modules are immediately usable by tools that work with CommonJS such as Node.js and webpack, you can use Rollup to compile to UMD or CommonJS format, and then point to that compiled version with the main property in your package.json file. If your package.json file also has a module field, ES-module-aware tools like Rollup and webpack will import the ES module version directly.


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Release Notes

By Lukas Taegert-Atkinson • Published on July 27, 2022


Bug Fixes

  • Avoid a rendering failure when mixing outputs with inlined and non-inlined dynamic imports (#4589)

Pull Requests

  • #4589: Handle generating non-inlined imports after inlined ones (@lukastaegert)
By Lukas Taegert-Atkinson • Published on July 26, 2022



Bug Fixes

  • Ensure IIFE output generates a global variable when generating ES5 (#4588)

Pull Requests

  • #4577: broken link removed (@Jawad-H)
  • #4580: Update dependencies (@lukastaegert)
  • #4584: Documentation clarity and syntax improvements (@berniegp)
  • #4588: Use var for IIFE (@lukastaegert)
By Lukas Taegert-Atkinson • Published on July 15, 2022



  • Introduce maxParallelFileOps to limit both read and write operations, default to 20 and replaces maxParallelFileRead (#4570)

Bug Fixes

  • Avoid including variables referenced from return statements that are never reached (#4573)

Pull Requests

  • #4570: Introduce maxParallelFileOps to limit parallel writes (@lukastaegert)
  • #4572: Document more ways to read package.json in ESM (@berniegp)
  • #4573: Do not include unused return expressions (@lukastaegert)
By Lukas Taegert-Atkinson • Published on July 8, 2022



  • Allow setting a sourcmapBaseUrl for absolute paths in sourcemaps (#4527)

Bug Fixes

  • Support absolute CLI plugin paths on Windows (#4533)

Pull Requests

  • #4527: Add sourcemapBaseUrl option (@nickgarlis)
  • #4533: Add support for absolute plugin paths (@ygoe)
  • #4538: chore: Included githubactions in the dependabot config (@naveensrinivasan)
  • #4546: Adapt Node versions on CI to prepare for v3 (@lukastaegert)
  • #4556: Improve error message for invalid patterns (@DysphoricUnicorn)
  • #4559: Update dependencies (@lukastaegert)
  • #4560: Bump peter-evans/create-or-update-comment from 1 to 2 (@dependabot)
  • #4561: Bump peter-evans/find-comment from 1 to 2 (@dependabot)
  • #4562: Bump codecov/codecov-action from 1 to 3 (@dependabot)
By Lukas Taegert-Atkinson • Published on June 20, 2022


Bug Fixes

  • Mark Array.prototype.group/groupToMap as side effect free. (#4531)

Pull Requests

  • #4523: chore: remove source map workaround, bump deps (@dnalborczyk)
  • #4525: Add regression tests for instanceof (@lukastaegert)
  • #4528: chore: Set permissions for GitHub actions (@naveensrinivasan)
  • #4531: fix: rename Array.prototype.group/groupToMap (@dnalborczyk)
  • #4535: chore: bump resolve from 1.22.0 to 1.22.1 (@pos777)
By Lukas Taegert-Atkinson • Published on June 7, 2022


Bug Fixes

  • Properly deoptimize "this" when using member expressions with getters/setters in for loops and update expressions (#4522)

Pull Requests

  • #4522: Refactor side effect handling for property interactions (@lukastaegert)
By Lukas Taegert-Atkinson • Published on June 1, 2022


Bug Fixes

  • Avoid crashes when using logical expressions for unused constructor arguments (#4519)
  • Fix missing parameter defaults for calls from try statements and functions returned by functions (#4520)

Pull Requests

  • #4519: Try to make logical expression deoptimization more robust (@lukastaegert)
  • #4520: Roll back parameter default tree shaking (@lukastaegert)
By Lukas Taegert-Atkinson • Published on May 31, 2022


Bug Fixes

  • Ensure parameter defaults are retained when a function is used as an object property (#4516)

Pull Requests

  • #4516: Deoptimize parameter defaults when referenced from object/array/class literals (@lukastaegert)
By Lukas Taegert-Atkinson • Published on May 29, 2022


Bug Fixes

  • Retain parameter defaults for functions that are defaults themselves (#4515)
  • Track mutations for objects as default values (#4515)

Pull Requests

  • #4515: Ensure parameter defaults are deoptimized (@lukastaegert)
By Lukas Taegert-Atkinson • Published on May 28, 2022


Pull Requests

  • #4513: Update link to node polyfill repo (@lukastaegert)


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Jul 27, 2022
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