# General Translation Platform: isSupersetLocale
URL: https://generaltranslation.com/en-US/docs/platform/core/reference/utility-functions/locales/is-superset-locale.mdx
---

title: isSupersetLocale
description: Check whether one locale can represent another more specific locale without a GT instance. API reference for isSupersetLocale.

---

[`isSupersetLocale`](/docs/platform/core/reference/gt-class-methods/locales/is-superset-locale) is a standalone utility function from General Translation's Core library that checks whether one locale is a superset of another in the BCP-47 hierarchy — that is, whether it can represent the more specific locale.

## Overview [#overview]

Import `isSupersetLocale` directly from `generaltranslation` and call it with a superset locale and a subset locale. It does not require an API key or a [GT](/docs/platform/core/reference/gt-class/constructor) instance. For the instance-based equivalent, use the [`isSupersetLocale`](/docs/platform/core/reference/gt-class-methods/locales/is-superset-locale) method on a [`GT`](/docs/platform/core/reference/gt-class/constructor) instance instead.

```typescript
import { isSupersetLocale } from 'generaltranslation';

console.log(isSupersetLocale('en', 'en-US')); // true
console.log(isSupersetLocale('en-US', 'en')); // false
```

Signature:

```typescript
isSupersetLocale(superLocale: string, subLocale: string): boolean
```

## How it works [#how-it-works]

- **Hierarchy check.** Uses the BCP-47 locale hierarchy. `subLocale` is a subset of `superLocale` if it is an extension of `superLocale` or is otherwise identical to it.
- **Base languages.** A base language is a superset of its regional variants, but a regional variant is not a superset of its base language.
- **Reflexive.** A locale is always a superset of itself.

## Parameters [#parameters]

| Parameter | Description | Type | Optional | Default |
| --- | --- | --- | --- | --- |
| [`superLocale`](#super-locale) | The locale to check as the potential superset. | `string` | No | — |
| [`subLocale`](#sub-locale) | The locale to check as the potential subset. | `string` | No | — |

### `superLocale` [#super-locale]

**Type** `string` · **Required**

The locale to check as the potential superset.

### `subLocale` [#sub-locale]

**Type** `string` · **Required**

The locale to check as the potential subset.

## Returns [#returns]

**Type** `boolean`

`true` if `superLocale` is a superset of `subLocale`, `false` otherwise.

## Examples [#examples]

```typescript
import { isSupersetLocale } from 'generaltranslation';

// Base language is a superset of a regional variant
console.log(isSupersetLocale('en', 'en-US')); // true
console.log(isSupersetLocale('es', 'es-ES')); // true

// Regional variant is NOT a superset of a base language
console.log(isSupersetLocale('en-US', 'en')); // false

// A locale is always a superset of itself
console.log(isSupersetLocale('en-US', 'en-US')); // true
```

## Notes [#notes]

- Uses the BCP-47 locale hierarchy.
- Base languages are supersets of regional variants.
- A locale is always a superset of itself.
- Essential for building fallback systems.