# generaltranslation: General Translation Core SDK: isSameDialect
URL: https://generaltranslation.com/en-GB/docs/core/class/methods/locales/is-same-dialect.mdx
---
title: isSameDialect
description: API reference for the GT isSameDialect method
---

## Overview

The `isSameDialect` method checks whether multiple BCP-47 locale codes represent the same dialect.
It compares the language and region components of locale codes to determine whether they represent the same linguistic variety.

***

## Reference

### Parameters

<TypeTable
  type={{
  "...locales": {
    type: '(string | string[])[]',
    optional: false,
  }
}}
/>

### Parameter descriptions

| Parameter    | Description                                                                                                                          |
| ------------ | ------------------------------------------------------------------------------------------------------------------------------------ |
| `...locales` | Variable number of locale codes (strings) or arrays of locale codes to compare. All provided locales must represent the same dialect |

### Returns

`boolean` - `true` if all provided locale codes represent the same dialect, `false` otherwise

### Throws

No exceptions are thrown. Invalid locale codes are handled gracefully and return `false`.

***

## Behaviour

### Dialect comparison logic

The method uses the following logic to determine dialect equality:

1. **Normalise locales** - Standardises all input locale codes
2. **Compare language codes** - All locales must have the same base language
3. **Handle region hierarchy** - A base language matches its regional variants
4. **Exact dialect matching** - Regional variants must match exactly

### Hierarchy rules

* Base language (`'en'`) matches any regional variant (`'en-US'`, `'en-GB'`)
* Regional variants match only exactly (`'en-US'` ≠ `'en-GB'`)
* Script variants are considered in the comparison when present
* Different languages never match (`'en'` ≠ `'es'`)

### Input flexibility

The method accepts:

* Multiple string parameters: `isSameDialect('en-US', 'en-GB')`
* Arrays of strings: `isSameDialect(['en-US', 'en-GB'])`
* Mixed format: `isSameDialect('en-US', ['en-GB', 'en-CA'])`
* Single locale: `isSameDialect('en-US')` (always returns `true`)

***

## Examples

### Basic dialect comparison

```typescript
const gt = new GT({
  sourceLocale: 'en-US',
  targetLocale: 'es-ES'
});

// Same exact dialects
console.log(gt.isSameDialect('en-US', 'en-US')); // true
console.log(gt.isSameDialect('zh-CN', 'zh-CN')); // true

// Different dialects of same language
console.log(gt.isSameDialect('en-US', 'en-GB')); // false
console.log(gt.isSameDialect('es-ES', 'es-MX')); // false
console.log(gt.isSameDialect('pt-PT', 'pt-BR')); // false

// Base language with regional variants
console.log(gt.isSameDialect('en', 'en-US')); // true
console.log(gt.isSameDialect('es', 'es-ES')); // true
console.log(gt.isSameDialect('zh', 'zh-CN')); // true

// Different languages
console.log(gt.isSameDialect('en-US', 'es-ES')); // false
console.log(gt.isSameDialect('fr-FR', 'de-DE')); // false
```

***


## Notes

* Uses standardised locale codes for accurate comparison
* Accepts flexible input formats (strings, arrays, mixed)

## Next steps

* Compare languages with [`isSameLanguage`](/docs/core/class/methods/locales/is-same-language)
* Check locale hierarchy with [`isSupersetLocale`](/docs/core/class/methods/locales/is-superset-locale)
* Validate locales with [`isValidLocale`](/docs/core/class/methods/locales/is-valid-locale)