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A package to help you find out which of your node_modules aren't written in ES5 so you can add them to your Webpack/Rollup/Parcel transpilation steps. This is currently limited to checking the entrypoint scripts only, which might actually be enough of a check to determine if a package should be transpiled or not.


You can install the package globally with

npm install -g are-you-es5

or if you'd rather just run it immediately you can use npx:

npx are-you-es5 check /path/to/some/repo


If you've installed it globally and find it tiresome to type are-you-es5 a lot, you can alias it to es5:

alias es5="are-you-es5"


Usage: are-you-es5 check [options] <path>

Checks if all node_modules (including monorepos) at <path> are ES5

  -a, --all             Check all node_modules instead of just direct dependencies
  -v, --verbose         Log all messages (including modules that are ES5)
  --no-regex-filtering  Stops all filtering on babel-loader exclude regex (does not hide anything)
  -r, --regex           Get babel-loader exclude regex to ignore all node_modules except non-ES5 ones, by default does not show any babel or webpack modules, use with --no-regex-filtering if you want to see everything
  --silent              Do not log messages in the console (except regex if --regex is used)
  -h, --help            output usage information

Usage as a Library

If you would like to use this package as a NodeJS library instead of a CLI dependency, you may use this snippet:

import {
} from 'are-you-es5'

const result = checkModules({
  path: '', // Automatically find up package.json from cwd
  checkAllNodeModules: true,
  ignoreBabelAndWebpackPackages: true

/** Returns the regexp including all es6 modules */
const es6IncludeRegExp = buildIncludeRegexp(result.es6Modules)

/** Returns the regexp excluding all es6 modules */
const es6ExcludeRegexp = buildExcludeRegexp(result.es6Modules)


are-you-es5 check /path/to/some/repo -r
❌ @babel/plugin-1 is not ES5
❌ @babel/plugin-2 is not ES5

Babel-loader exclude regex:



Upgrading from 1.1

If you were on version 1.1, the -a or -all option used to be for logging all messages, this has now changed to -v or --verbose and -a and -all are now used as a flag to check all node modules.

Upgrading to 1.3

1.3 Now by default skips checking anything that has the word babel or webpack, or if a string ends with loader. To restore previous behavior use the --no-regex-filtering option.

Upgrading from 2.0 to 2.1

This upgrade only affects you if you were using the package as a library (instead of just a CLI tool), checkModules now returns an object that has 3 arrays: es5Modules, es6Modules, and ignored. To preserve previous behavior use es6Modules, see the Usage as a Library section.


  • acorn - All the actual ES5 checking happens through acorn, this package wouldn't exist without it.
  • es-check - This whole package wouldn't have been possible if I hadn't come across es-check and learned from it.

Contributors ✨

Thanks goes to these wonderful people (emoji key):



Paolo Priotto


Yuki Hattori


Renan Bandeira


Yao Zhao


This project follows the all-contributors specification. Contributions of any kind welcome!


A package to help you find out which of your node_modules aren't ES5 so you can add them to your Webpack/Rollup/Parcel transpilation steps.








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