# generaltranslation: General Translation Core SDK: standardizeLocale
URL: https://generaltranslation.com/en-US/docs/core/class/methods/locales/standardize-locale.mdx
---
title: standardizeLocale
description: API reference for the GT standardizeLocale method
---

## Overview

The `standardizeLocale` method standardizes a BCP-47 locale code to ensure correct formatting and casing.
It converts locale codes to their proper canonical format, making them suitable for use with internationalization APIs and ensuring consistency across your application.

---

## Reference

### Parameters

<TypeTable
  type={{
    "locale?": {
      type: 'string',
      optional: true,
      default: 'this.targetLocale'
    }
  }}
/>

### Parameters description

| Parameter | Description |
|-----------|-------------|
| `locale` | The BCP-47 locale code to standardize. If not provided, uses the instance's `targetLocale` |

### Returns

`string` - The standardized BCP-47 locale code, or empty string if the input is invalid

### Throws

- `Error` - If no locale is provided and the instance has no `targetLocale` configured

---

## Behavior

Common format corrections applied:
- `en_US` → `en-US` (underscore to hyphen)
- `zh_cn` → `zh-CN` (underscore to hyphen, casing)
- `EN-gb` → `en-GB` (language lowercase, region uppercase)
- `Fr-ca` → `fr-CA` (proper casing throughout)
- `ja_jp` → `ja-JP` (underscore and casing)

---

## Examples

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

// Standardize various locale formats
console.log(gt.standardizeLocale('en_us')); // "en-US"
console.log(gt.standardizeLocale('zh_cn')); // "zh-CN"
console.log(gt.standardizeLocale('EN-gb')); // "en-GB"
console.log(gt.standardizeLocale('fr-ca')); // "fr-CA"

// Already standardized locales pass through unchanged
console.log(gt.standardizeLocale('es-ES')); // "es-ES"
console.log(gt.standardizeLocale('ja-JP')); // "ja-JP"
```

---

## Notes

- Converts underscores to hyphens and normalizes casing
- Returns empty string for invalid locale codes
- Language codes become lowercase, region codes become uppercase
- Preserves locale extensions and variants when present

## Next steps

- Validate standardized locales with [`isValidLocale`](/docs/core/class/methods/locales/is-valid-locale)
- Resolve canonical locales with [`resolveCanonicalLocale`](/docs/core/class/methods/locales/resolve-canonical-locale)
- Get locale properties with [`getLocaleProperties`](/docs/core/class/methods/locales/get-locale-properties)