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

## Overview

The `isValidLocale` function validates whether a given string represents a valid BCP-47 locale code. It performs comprehensive format validation without requiring a GT class instance.

***

## Reference

### Parameters

<TypeTable
  type={{
  "locale": {
    type: 'string',
    optional: false,
  },
  "customMapping?": {
    type: 'CustomMapping',
    optional: true,
  }
}}
/>

### Returns

`boolean` - `true` if the locale code is valid, `false` otherwise

***

## Examples

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

// Valid locale codes
console.log(isValidLocale('en-US')); // true
console.log(isValidLocale('zh-CN')); // true
console.log(isValidLocale('es')); // true

// Invalid locale codes
console.log(isValidLocale('invalid')); // false
console.log(isValidLocale('en_US')); // false (underscore instead of hyphen)
console.log(isValidLocale('')); // false
```

***


## Notes

* Validates BCP-47 locale code format
* Works with custom locale mappings
* Essential for user input validation
* No network requests – pure format validation
* Stateless function suitable for utility libraries

## Next steps

* Use the GT class method [`isValidLocale`](/docs/core/class/methods/locales/is-valid-locale)
* Standardise the format with [`standardizeLocale`](/docs/core/functions/locales/standardize-locale)