# generaltranslation: General Translation Core SDK: isSupersetLocale
URL: https://generaltranslation.com/en-GB/docs/core/functions/locales/is-superset-locale.mdx
---
title: isSupersetLocale
description: API reference for the isSupersetLocale function
---

## Overview

The `isSupersetLocale` function checks whether one locale is a superset of another in the BCP-47 hierarchy without requiring a GT class instance.

***

## Reference

### Parameters

<TypeTable
  type={{
  "superLocale": {
    type: 'string',
    optional: false,
  },
  "subLocale": {
    type: 'string',
    optional: false,
  }
}}
/>

### Returns

`boolean` - `true` if superLocale is a superset of subLocale

***

## Examples

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

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

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

// Same locales are supersets of themselves
console.log(isSupersetLocale('en-US', 'en-US')); // true
```

***


## Notes

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

## Next steps

* Use the GT class method [`isSupersetLocale`](/docs/core/class/methods/locales/is-superset-locale)
* Compare languages with [`isSameLanguage`](/docs/core/functions/locales/is-same-language)