Abstract base class representing the configuration for an AI service backend. This class should not be instantiated directly. Use its subclasses; [GoogleAIBackend](https://firebase.google.com/docs/reference/js/ai.googleaibackend#googleaibackend_class) for the Gemini Developer API (via [Google AI](https://ai.google/)) and [AgentPlatformBackend](https://firebase.google.com/docs/reference/js/ai.agentplatformbackend#agentplatformbackend_class) for the Agent Platform Gemini API.

**Signature:**

    export declare abstract class Backend 

## Constructors

| Constructor | Modifiers | Description |
|---|---|---|
| [(constructor)(type)](https://firebase.google.com/docs/reference/js/ai.backend#backendconstructor) |   | Protected constructor for use by subclasses. |

## Properties

| Property | Modifiers | Type | Description |
|---|---|---|---|
| [backendType](https://firebase.google.com/docs/reference/js/ai.backend#backendbackendtype) |   | [BackendType](https://firebase.google.com/docs/reference/js/ai#backendtype) | Specifies the backend type. |

## Backend.(constructor)

Protected constructor for use by subclasses.

**Signature:**

    protected constructor(type: BackendType);

#### Parameters

| Parameter | Type | Description |
|---|---|---|
| type | [BackendType](https://firebase.google.com/docs/reference/js/ai#backendtype) | The backend type. |

## Backend.backendType

Specifies the backend type.

**Signature:**

    readonly backendType: BackendType;