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Intl.NumberFormat (ESNext)

A polyfill for ESNext Intl.NumberFormat and Number.prototype.toLocaleString.

npm Version size


npm i @formatjs/intl-numberformat


This package requires the following capabilities:


Everything in the ES2020 Internationalization API spec (



You can use URL Builder to create a polyfill script tag for Intl.NumberFormat. By default the created URL does not come with any locale data. In order to add locale data, append Intl.NumberFormat.~locale.<locale>, as well as locale data for any required polyfills, to your list of features. For example:

<!-- Polyfill Intl.NumberFormat, its dependencies & `en` locale data -->
<script src=",Intl.NumberFormat.~locale.en"></script>

Or if Intl.PluralRules needs to be polyfilled as well:

<!-- Polyfill Intl.NumberFormat, its dependencies & `en` locale data -->
<script src=",Intl.NumberFormat.~locale.en,Intl.PluralRules.~locale.en"></script>


import '@formatjs/intl-numberformat/polyfill'
import '@formatjs/intl-numberformat/locale-data/en' // locale-data for en

Dynamic import + capability detection

import {shouldPolyfill} from '@formatjs/intl-numberformat/should-polyfill'
async function polyfill(locale: string) {
const unsupportedLocale = shouldPolyfill(locale)
// This locale is supported
if (!unsupportedLocale) {
// Load the polyfill 1st BEFORE loading data
await import('@formatjs/intl-numberformat/polyfill-force')
await import(`@formatjs/intl-numberformat/locale-data/${unsupportedLocale}`)

Supported Units

Simple Units

Currently, the spec defines a list of sanctioned units as below.

type Unit =
| 'acre'
| 'bit'
| 'byte'
| 'celsius'
| 'centimeter'
| 'day'
| 'degree'
| 'fahrenheit'
| 'fluid-ounce'
| 'foot'
| 'gallon'
| 'gigabit'
| 'gigabyte'
| 'gram'
| 'hectare'
| 'hour'
| 'inch'
| 'kilobit'
| 'kilobyte'
| 'kilogram'
| 'kilometer'
| 'liter'
| 'megabit'
| 'megabyte'
| 'meter'
| 'mile'
| 'mile-scandinavian'
| 'millimeter'
| 'milliliter'
| 'millisecond'
| 'minute'
| 'month'
| 'ounce'
| 'percent'
| 'petabyte'
| 'pound'
| 'second'
| 'stone'
| 'terabit'
| 'terabyte'
| 'week'
| 'yard'
| 'year'

Compound Units

You can specify X-per-Y unit, where X and Y are sanctioned simple units (e.g. kilometer-per-hour). The library will choose the best-fit localized pattern to format this compound unit.