webpack-license-plugin

Manage third-party license compliance in your Webpack build

Are you using Rollup or Vite? have a look at rollup-license-plugin!

Key Features • Installation • How to use • Available options • Examples

Key features

This plugin extracts open source license information about all of the packages in your webpack output and helps you identify and fix problems with your open source licensing policy.

This plugin has full unit and end to end test coverage and is tested with webpack 2, 3, 4 and 5. It will help you:

• Discover every package used in your webpack output
• Find out how it is licensed
• Cancel builds that include unacceptable licenses
• Exclude internal packages from being scanned
• Create a customized inventory (usually called bill of materials) in json, html, csv or other formats

Installation

Install webpack-license-plugin as a development dependency to your current project

npm

$ npm install -D webpack-license-plugin

Yarn

$ yarn add -D webpack-license-plugin

How to use

Use webpack-license-plugin in your webpack configuration by adding it to the plugins array.

const LicensePlugin = require('webpack-license-plugin')

module.exports = {
  plugins: [
    // there might be other plugins here
    new LicensePlugin()
  ],
}

Available options

Options are given as an Object to the first parameter of the LicensePlugin constructor:

const licensePlugin = new LicensePlugin({ outputFilename: 'thirdPartyNotice.json' })

The available options are:

Name	Description
additionalFiles	Default: {}. Object that defines additional files that should be generated by this plugin based on it's default output (e.g. an html representation of the licenses in addition to the generated json). Keys represent filenames, values are functions that get invoked with the packages array and should return the content written to the additional file. These functions can be async or return a Promise.
excludedPackageTest	A method to exclude packages from the process. It is invoked with packageName (string) and version (string) of every package and should return true to exclude the package.
licenseOverrides	Default: {}. Object with licenses to override. Keys have the format <name>@<version>, values are valid spdx license expressions. This can be helpful when license information is inconclusive and has been manually checked.
outputFilename	Default: oss-licenses.json. Path to the output file that will be generated. Relative to the bundle output directory.
replenishDefaultLicenseTexts	Default: false. When this is enabled, default license texts are taken from spdx.org for packages where no license text was found.
unacceptableLicenseTest	A method to define license identifiers as unacceptable. It is invoked with licenseIdentifier (string) for every package and should return true when the license is unacceptable and encountering it should fail the build.
includePackages	Default: () => []. A method to define packages that should always be included in the output. It must return an array containing the absolute paths of those packages. This function can be async or return a Promise.
includeNoticeText	Default: false. When this is enabled, notice file text is included as part of the output.

Example with custom options

This example writes the result to a file named meta/licenses.json in the output directory, fails whenever it encounters one of the given licenses and overrides the license of the package [email protected].

const LicensePlugin = require('webpack-license-plugin')

module.exports = {
  // ...
  plugins: [
    new LicensePlugin({
      excludedPackageTest: (packageName, version) => {
        return packageName.startsWith('@internal/')
      },
      licenseOverrides: {
        // has "Apache" in package.json, but Apache-2.0 text in LICENSE file
        '[email protected]': 'Apache-2.0'
      },
      outputFilename: 'meta/licenses.json',
      unacceptableLicenseTest: (licenseIdentifier) => {
        return ['GPL', 'AGPL', 'LGPL', 'NGPL'].includes(licenseIdentifier)
      }
    }),
  ],
}

Default output

The output is a oss-licenses.json file in the webpack build output directory. It contains an array of packages that were found to be part of the webpack output and lists several license-related details for every package:

Name	Description
name	package name
version	package version
author	author listed in package.json (if available)
repository	repository url listed in package.json (if available)
source	package tarball url on npm registry
license	the license listed in package.json. If this is not a valid spdx license expression, this plugin will inform you. You can then inform the package maintainers about this problem and temporarily workaround this issue with the licenseOverrides option for the specific combination of package name and version.
licenseText	the license text read from a file matching /^licen[cs]e/i in the package's root
noticeText	if includeNoticeText option is set: the notice text read from a file matching /^notice/i in the package's root

Example output file

[
  {
    "name": "fbjs",
    "version": "0.8.17",
    "repository": "https://github.com/facebook/fbjs",
    "source": "https://registry.npmjs.org/fbjs/-/fbjs-0.8.17.tgz",
    "license": "MIT",
    "licenseText": "...",
    "noticeText": "..."
  },
  {
    "name": "object-assign",
    "version": "4.1.1",
    "author": "Sindre Sorhus",
    "repository": "https://github.com/sindresorhus/object-assign",
    "source": "https://registry.npmjs.org/object-assign/-/object-assign-4.1.1.tgz",
    "license": "MIT",
    "licenseText": "...",
    "noticeText": "..."
  },
  {
    "name": "react-dom",
    "version": "16.4.2",
    "repository": "https://github.com/facebook/react",
    "source": "https://registry.npmjs.org/react-dom/-/react-dom-16.4.2.tgz",
    "license": "MIT",
    "licenseText": "...",
    "noticeText": "..."
  },
  {
    "name": "react",
    "version": "16.4.2",
    "repository": "https://github.com/facebook/react",
    "source": "https://registry.npmjs.org/react/-/react-16.4.2.tgz",
    "license": "MIT",
    "licenseText": "...",
    "noticeText": "..."
  }
]

Examples

additionalFiles examples

When the additionalFiles option is set, the output shown above is passed into the transform function as an array for every additional file configured.

This way, the output can be formatted to any format you might need and then be written to one or more additional files.

Package list as CSV

const LicensePlugin = require('webpack-license-plugin')

function csvTransform(packages) {
  const keys = ['name', 'version', 'license']

  return [
    '"sep=,"',
    keys.join(','),
    ...packages.map(pckg => keys.map(key => `="${pckg[key]}"`).join(',')),
  ].join('\n')
}

module.exports = {
  // ...
  plugins: [
    new LicensePlugin({
      additionalFiles: {
        'oss-licenses.csv': csvTransform
      }
    }),
  ],
}

Package list and additional summary

const LicensePlugin = require('webpack-license-plugin')

module.exports = {
  // ...
  plugins: [
    new LicensePlugin({
      additionalFiles: {
        'oss-summary.json': (packages) => {
          return JSON.stringify(
            packages.reduce(
              (prev, { license }) => ({
                ...prev,
                [license]: prev[license] ? prev[license] + 1 : 1,
              }),
              {}
            ),
            null,
            2
          )
        },
      },
    }),
  ],
}