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Browserslist is a standard way to define a set of target browsers or runtimes using a query string. core-js integrates with browserslist through the core-js-compat package, which resolves browserslist queries into the exact set of core-js modules needed.

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The targets option

The targets option accepted by core-js-compat (and passed through from @babel/preset-env) accepts two formats: a browserslist query string or a plain object specifying minimum engine versions.

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Browserslist query string

Pass any valid browserslist query as a string: 
import compat from 'core-js-compat';

const { list } = compat({
  targets: 'defaults, not IE 11, maintained node versions',
});
Common query examples: 
// Market share threshold
'> 1%'

// Last N versions of each browser
'last 2 versions'

// Specific browsers with exclusions
'defaults, not IE 11, maintained node versions'

// Extended coverage
'> 0.5%, last 2 versions, Firefox ESR, not dead'

​
Target object format

Alternatively, pass an object with explicit minimum versions for each engine. All fields are optional: 
const { list, targets } = compat({
  targets: {
    android: '4.0',          // Android WebView version
    bun: '0.1.2',            // Bun version
    chrome: '38',            // Chrome version
    'chrome-android': '18',  // Chrome for Android version
    deno: '1.12',            // Deno version
    edge: '13',              // Edge version
    electron: '5.0',         // Electron framework version
    firefox: '15',           // Firefox version
    'firefox-android': '4',  // Firefox for Android version
    hermes: '0.11',          // Hermes version
    ie: '8',                 // Internet Explorer version
    ios: '13.0',             // iOS Safari version
    node: 'current',         // Node.js version; 'current' uses the running version
    opera: '12',             // Opera version
    'opera-android': '7',    // Opera for Android version
    phantom: '1.9',          // PhantomJS headless browser version
    quest: '5.0',            // Meta Quest Browser version
    'react-native': '0.70',  // React Native version (default Hermes engine)
    rhino: '1.7.13',         // Rhino engine version
    safari: '14.0',          // Safari version
    samsung: '14.0',         // Samsung Internet version
  },
});

​
The esmodules and browsers sub-keys

The target object also supports two special keys: 
{
  /**
   * true: target minimum ES Modules-supporting versions of all browsers,
   *       ignoring the `browsers` key.
   * 'intersect': intersect the `browsers` target with browserslist's targets,
   *              taking the maximum version.
   */
  esmodules: true | 'intersect',

  // Nested browserslist query or object for browser targets
  browsers: '> 0.25%',
}

​
What compat() returns

The function returns two values:
  • list — an array of core-js module names that are required for the given targets
  • targets — an object mapping each required module name to the specific engine versions that still need it
import compat from 'core-js-compat';

const { list, targets } = compat({
  targets: '> 1%',
});

console.log(targets);
/* =>
{
  'es.error.cause': { ios: '14.5-14.8' },
  'es.aggregate-error.cause': { ios: '14.5-14.8' },
  'es.array.at': { ios: '14.5-14.8' },
  'es.array.find-last': { firefox: '100', ios: '14.5-14.8' },
  'es.array.find-last-index': { firefox: '100', ios: '14.5-14.8' },
  'es.array.includes': { firefox: '100' },
  'es.array.push': { chrome: '100', edge: '101', ios: '14.5-14.8', safari: '15.4' },
  'es.array.unshift': { ios: '14.5-14.8', safari: '15.4' },
  'es.object.has-own': { ios: '14.5-14.8' },
  'es.regexp.flags': { chrome: '100', edge: '101' },
  'es.string.at-alternative': { ios: '14.5-14.8' },
  'es.typed-array.at': { ios: '14.5-14.8' },
  'esnext.array.group': { chrome: '100', edge: '101', firefox: '100', ios: '14.5-14.8', safari: '15.4' },
  'web.dom-exception.stack': { chrome: '100', edge: '101', ios: '14.5-14.8', safari: '15.4' },
  'web.immediate': { chrome: '100', edge: '101', firefox: '100', ios: '14.5-14.8', safari: '15.4' },
  'web.structured-clone': { chrome: '100', edge: '101', firefox: '100', ios: '14.5-14.8', safari: '15.4' },
  // ...
}
*/

​
Filtering modules

Use the modules and exclude options to narrow the query to a subset of core-js: 
const { list } = compat({
  targets: '> 1%',
  modules: [
    'core-js/actual',         // entry point (expands to all modules it covers)
    'esnext.array.unique-by', // exact module name (or prefix)
    /^web\./,                 // regex matched against module names
  ],
  exclude: [
    'web.atob',
  ],
  version: '3.49',            // core-js version to use; defaults to latest
});

​
Integration with @babel/preset-env

When you configure @babel/preset-env with useBuiltIns: 'usage' or useBuiltIns: 'entry', it reads your browserslist configuration and uses core-js-compat internally to determine which polyfills to inject. The targets option in @babel/preset-env accepts the same formats described above. 
// babel.config.js
module.exports = {
  presets: [
    [
      '@babel/preset-env',
      {
        useBuiltIns: 'usage',
        corejs: '3.49',
        targets: 'defaults, not IE 11, maintained node versions',
      },
    ],
  ],
};
You can also set targets as an object in your Babel config to pin specific minimum versions, bypassing the .browserslistrc file entirely.

core-js-compat package

Full API reference including additional exports like data, entries, and getModulesListForTargetVersion.

Babel integration

How to configure @babel/preset-env with core-js for automatic polyfill injection.