29.0.4 • Public • Published

@modular-css/rollup NPM Version NPM License NPM Downloads

Rollup support for modular-css.


> npm i @modular-css/rollup

⚠️Rollup Version support⚠️

Due to API changes, certain major versions of this plugin will require a specific minimum rollup version. This is expressed within the peerDependency field in package.json and replicated here for ease of reference.

  • @modular-css/rollup@19 requires rollup@1.0.0
  • @modular-css/rollup@18 requires rollup@0.68.0
  • @modular-css/rollup@15 requires rollup@0.65.0
  • @modular-css/rollup@11 requires rollup@0.60.0



const bundle = await rollup({
    input   : "./index.js",
    plugins : [

Config file

import css from "@modular-css/rollup";

export default {
    input   : "./index.js",
    output  : {
        dest    : "./gen/bundle.js",
        format  : "umd"
    plugins : [

In your code

Write your modular-css styles in a .css file

/* style.css */
@value error: red;

.rule {
    border: 1px solid error;

import it from your JS, either as named exports

// Named exports
import { rule, $values } from "./style.css";

console.log(rule); // .mc_abcdefrule
console.log($values); // { error : "red" }

or using the default export

// Default export
import css from "./style.css";

console.log(css.rule); // .mc_abcdefrule
console.log(css.$values); // { error : "red" }



File name to use in case there are any CSS dependencies that appear in multiple bundles. Defaults to "common.css".


Enable dev mode. In dev mode the default export of a CSS file will be a Proxy instead of a bare object. Attempts to access non-existant properties on the proxy will throw a ReferenceError to assist in catching missing class references.


A minimatch pattern, or an array of minimatch patterns, relative to process.cwd(). include defaults to **/*.css.


Boolean/String to determine if JSON files containing all exported classes & values should be output. If set to true will write out to a file named exports.json. If a String will write out to that file name. Defaults to false.


Boolean to determine if inline source maps should be included. Defaults to true.

To force the creation of external source maps set the value to { inline : false }.


Boolean/String to determine if chunk metadata should be output. If set to true will write out a file named metadata.json. If a String will write out to that file name. Defaults to false.

Currently the only metadata being written is CSS dependencies, but that may change in the future.


The rollup plugin will rewrite invalid identifiers using identifierfy by default. You can disable this behavior by setting namedExports to { rewriteInvalid : false }.


By default this plugin will extract and bundle CSS in a separate file. If you would like the styles from each imported CSS file to be exported as a string for use in JS, you can enable this by setting styleExport to true. If you are using this option the after & done hooks will not run against the exported styles, you should perform any additional CSS transformations in the processing hook instead.

import { styles } from "./styles.css";

Enable styleExport will also disable the plugin from emitting any assets as well as sourcemaps (unless you explicitly opt-in to sourcemaps via the map option)


You can disable exporting classes as default export, eg import styles from "./style.css";, by setting defaultExport to false. Defaults to true.


You can set variable declaration kind, eg var mc_rule = ...;, by setting variableDeclaration to var. Defaults to const.


Set to true to enable writing out CSS files that don't contain any content (like if you have a CSS file that contains only @value rules).


Pass an already-instantiated Processor instance to the rollup plugin. It will then add any files found when traversing the modules to it and both the rollup-discovered and any already-existing files will be output in the final CSS.


Enable verbose logging while running to help diagnose issues

Shared Options

All other options are passed to the underlying Processor instance, see Options.

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npm i @modular-css/rollup



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