# General Translation Platform: GTConstructorParams
URL: https://generaltranslation.com/en-US/docs/platform/core/reference/types/gt-constructor-params.mdx
---

title: GTConstructorParams
description: Configuration options accepted by the GT constructor. API reference for GTConstructorParams type.

---

`GTConstructorParams` defines the configuration options accepted by the General Translation [Constructor](/docs/platform/core/reference/gt-class/constructor) when initializing a [`GT`](/docs/platform/core/reference/gt-class/constructor) instance.

## Overview [#overview]

All properties are optional. When `apiKey`, `devApiKey`, and `projectId` are not provided, the constructor reads them from the `GT_API_KEY`, `GT_DEV_API_KEY`, and `GT_PROJECT_ID` environment variables.

```typescript
type GTConstructorParams = {
  apiKey?: string;
  devApiKey?: string;
  sourceLocale?: string;
  targetLocale?: string;
  locales?: string[];
  projectId?: string;
  baseUrl?: string;
  customMapping?: CustomMapping;
};
```

*Note:* the older docs typed this as an `interface`; the current source defines it as a `type` alias.

## Properties [#properties]

| Property | Description | Type | Optional |
| --- | --- | --- | --- |
| [`apiKey`](#api-key) | Production API key. | `string` | Yes |
| [`devApiKey`](#dev-api-key) | Development API key. | `string` | Yes |
| [`sourceLocale`](#source-locale) | Default source locale. | `string` | Yes |
| [`targetLocale`](#target-locale) | Default target locale. | `string` | Yes |
| [`locales`](#locales) | Supported locale codes. | `string[]` | Yes |
| [`projectId`](#project-id) | Project identifier. | `string` | Yes |
| [`baseUrl`](#base-url) | Custom API endpoint. | `string` | Yes |
| [`customMapping`](#custom-mapping) | Custom locale mappings. | [`CustomMapping`](/docs/platform/core/reference/types/custom-mapping) | Yes |

### `apiKey` [#api-key]

**Type** `string` · **Optional**

Production API key for the translation service. Falls back to the `GT_API_KEY` environment variable.

### `devApiKey` [#dev-api-key]

**Type** `string` · **Optional**

Development API key. Falls back to the `GT_DEV_API_KEY` environment variable.

### `sourceLocale` [#source-locale]

**Type** `string` · **Optional**

Default source locale for translations.

### `targetLocale` [#target-locale]

**Type** `string` · **Optional**

Default target locale for translations.

### `locales` [#locales]

**Type** `string[]` · **Optional**

Array of supported locale codes.

### `projectId` [#project-id]

**Type** `string` · **Optional**

Project identifier. Falls back to the `GT_PROJECT_ID` environment variable.

### `baseUrl` [#base-url]

**Type** `string` · **Optional**

Custom API endpoint, used for Enterprise deployments.

### `customMapping` [#custom-mapping]

**Type** [`CustomMapping`](/docs/platform/core/reference/types/custom-mapping) · **Optional**

Custom locale code mappings and locale property overrides. See [`CustomMapping`](/docs/platform/core/reference/types/custom-mapping).

## Example [#example]

```typescript
// Basic setup
const gt = new GT({
  apiKey: 'your-api-key',
  sourceLocale: 'en',
  targetLocale: 'es',
  locales: ['en', 'es', 'fr']
});
```

```typescript
// With environment variables
const gt = new GT({
  sourceLocale: 'en',
  targetLocale: 'es'
});
// Uses GT_API_KEY and GT_PROJECT_ID from the environment
```