Intl.getCanonicalLocales()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since October 2017.

The Intl.getCanonicalLocales() static method returns an array containing the canonical locale names. Duplicates will be omitted and elements will be validated as structurally valid language tags.

Try it

console.log(Intl.getCanonicalLocales("EN-US"));
// Expected output: Array ["en-US"]

console.log(Intl.getCanonicalLocales(["EN-US", "Fr"]));
// Expected output: Array ["en-US", "fr"]

try {
  Intl.getCanonicalLocales("EN_US");
} catch (err) {
  console.log(err.toString());
  // Expected output (Firefox/Safari): RangeError: invalid language tag: "EN_US"
  // Expected output (Chrome): RangeError: Incorrect locale information provided
}

Syntax

Intl.getCanonicalLocales(locales)

Parameters

locales: A list of String values for which to get the canonical locale names.

Return value

An array containing the canonical locale names.

Examples

Using getCanonicalLocales

Intl.getCanonicalLocales("EN-US"); // ["en-US"]
Intl.getCanonicalLocales(["EN-US", "Fr"]); // ["en-US", "fr"]

Intl.getCanonicalLocales("EN_US");
// RangeError:'EN_US' is not a structurally valid language tag

Specifications

Specification
ECMAScript® 2026 Internationalization API Specification # sec-intl.getcanonicallocales