# General Translation Platform: isSameLanguage
URL: https://generaltranslation.com/en-US/docs/platform/core/reference/utility-functions/locales/is-same-language.mdx
---

title: isSameLanguage
description: Check whether two locales share the same base language without a GT instance. API reference for isSameLanguage.

---

[`isSameLanguage`](/docs/platform/core/reference/gt-class-methods/locales/is-same-language) is a standalone utility function from General Translation's Core library that checks whether multiple BCP-47 locale codes represent the same base language, ignoring regional differences.

## Overview [#overview]

Import `isSameLanguage` directly from `generaltranslation` and call it with two or more locale codes. 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 [`isSameLanguage`](/docs/platform/core/reference/gt-class-methods/locales/is-same-language) method on a [`GT`](/docs/platform/core/reference/gt-class/constructor) instance instead.

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

console.log(isSameLanguage('en-US', 'en-GB')); // true
console.log(isSameLanguage('en-US', 'es-ES')); // false
```

Signature:

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

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

- **Base language comparison.** Compares only the base language codes (before the first hyphen), ignoring regional, script, and variant differences.
- **Variadic input.** Accepts a variable number of arguments, each of which may be a locale string or an array of locale strings.

## Parameters [#parameters]

| Parameter | Description | Type | Optional | Default |
| --- | --- | --- | --- | --- |
| [`locales`](#locales) | Two or more locale codes to compare. | `(string \| string[])[]` | No | — |

### `locales` [#locales]

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

The rest parameter of locale codes to compare. Each argument may be a locale string or an array of locale strings.

## Returns [#returns]

**Type** `boolean`

`true` if all locale codes represent the same base language, `false` otherwise.

## Examples [#examples]

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

// Same language, different regions
console.log(isSameLanguage('en-US', 'en-GB')); // true
console.log(isSameLanguage('es-ES', 'es-MX')); // true
console.log(isSameLanguage('zh-CN', 'zh-TW')); // true

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

## Notes [#notes]

- Compares only base language codes (before the first hyphen).
- Ignores regional, script, and variant differences.
- Essential for language-based content organization.
- Works with a variable number of parameters.