# generaltranslation: General Translation Core SDK: CustomMapping
URL: https://generaltranslation.com/en-US/docs/core/types/custom-mapping.mdx
---
title: CustomMapping
description: Type definition for custom locale code mappings and enhanced locale metadata
---

## Overview

`CustomMapping` defines custom locale code mappings and metadata that extends or overrides standard BCP-47 locale information.

```typescript
type CustomMapping = Record<string, string | Partial<LocaleProperties>>;
```

## Type definition

### Structure

`CustomMapping` is a record where:
- **Keys**: Custom locale codes or aliases (e.g., `'simplified-chinese'`, `'company-english'`)
- **Values**: Either a simple string name or partial `LocaleProperties` object

### Value types

| Type | Description | Example |
|------|-------------|---------|
| `string` | Simple display name | `'Simplified Chinese'` |
| `Partial<LocaleProperties>` | Enhanced locale metadata | `{ code: 'zh-CN', name: 'Chinese', emoji: '🇨🇳' }` |

---

## Examples

### Simple string mappings

```typescript copy
const simpleMapping: CustomMapping = {
  'english': 'English',
  'spanish': 'Spanish',
  'mexican-spanish': 'Mexican Spanish'
};

const gt = new GT({
  sourceLocale: 'english',
  targetLocale: 'spanish',
  customMapping: simpleMapping
});
```

### Enhanced locale metadata

```typescript copy
const enhancedMapping: CustomMapping = {
  'simplified-chinese': {
    code: 'zh-CN',
    name: 'Simplified Chinese',
    nativeName: '简体中文',
    regionName: 'China',
    emoji: '🇨🇳'
  }
};
```

---

## Notes

* Custom mappings override standard BCP-47 locale resolution
* String values provide simple display names
* Partial LocaleProperties allow detailed locale customization
* Custom mappings are resolved during GT instance initialization

## Related types

* [`LocaleProperties`](/docs/core/types/locale-properties) - Complete locale metadata structure