# General Translation Platform: isSameDialect
URL: https://generaltranslation.com/en-US/docs/platform/core/reference/gt-class-methods/locales/is-same-dialect.mdx
Docs index: https://generaltranslation.com/llms.txt
Description: Check whether two locales represent the same dialect. API reference for isSameDialect.

General Translation compares the language and region components of locale codes to determine whether they represent the same linguistic variety.

## Overview [#overview]

Call `isSameDialect` on a [`GT`](/docs/platform/core/reference/gt-class/constructor) instance with two or more locale codes (or arrays of codes). It returns `true` when they all represent the same dialect.

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

console.log(gt.isSameDialect('en-US', 'en-GB')); // false
console.log(gt.isSameDialect('en', 'en-US')); // true
```

Signature:

```typescript
isSameDialect(...locales: (string | string[])[]): boolean
```

*Note: `isSameDialect` runs locally and does not require an API key. Invalid locale codes are handled gracefully and return `false`. For comparisons without a `GT` instance, see the standalone [`isSameDialect`](/docs/platform/core/reference/utility-functions/locales/is-same-dialect).*

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

### Dialect comparison logic

The method determines dialect equality as follows:

1. **Normalize locales** — standardizes 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

- A 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'])`
- A single locale: `isSameDialect('en-US')` (always returns `true`)

## Parameters [#parameters]

| Parameter | Description | Type | Optional | Default |
| --- | --- | --- | --- | --- |
| [`locales`](#locales) | Variable number of locale codes, or arrays of locale codes, to compare. | `(string \| string[])[]` | No | — |

### `...locales` [#locales]

**Type** `(string | string[])[]` · **Required**

A variable number of locale codes (strings) or arrays of locale codes to compare. All provided locales must represent the same dialect.

## Returns [#returns]

**Type** `boolean`

`true` if all provided locale codes represent the same dialect, `false` otherwise. No exceptions are thrown; invalid locale codes are handled gracefully and return `false`.

## Examples [#examples]

```typescript
// Basic dialect comparison
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 [#notes]

- Uses standardized locale codes for accurate comparison.
- Accepts flexible input formats (strings, arrays, mixed).

## Sitemap

See the full [sitemap](https://generaltranslation.com/sitemap.md) for all pages.