voluptasmollitia/docs-exp/app.initializeapp.md

Monorepo for the Firebase JavaScript SDK

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[Home](./index.md) &gt; [@firebase/app](./app.md) &gt; [initializeApp](./app.initializeapp.md)

## initializeApp() function

Creates and initializes a FirebaseApp instance.

See [Add Firebase to your app](https://firebase.google.com/docs/web/setup#add_firebase_to_your_app) and [Initialize multiple projects](https://firebase.google.com/docs/web/setup#multiple-projects) for detailed documentation.

<b>Signature:</b>

```typescript
export declare function initializeApp(options: FirebaseOptions, name?: string): FirebaseApp;
```

## Parameters

|  Parameter | Type | Description |
|  --- | --- | --- |
|  options | [FirebaseOptions](./app.firebaseoptions.md) | Options to configure the app's services. |
|  name | string | Optional name of the app to initialize. If no name is provided, the default is <code>&quot;[DEFAULT]&quot;</code>. |

<b>Returns:</b>

[FirebaseApp](./app.firebaseapp.md)

The initialized app.

## Example 1


```javascript

// Initialize default app
// Retrieve your own options values by adding a web app on
// https://console.firebase.google.com
initializeApp({
  apiKey: "AIza....",                             // Auth / General Use
  authDomain: "YOUR_APP.firebaseapp.com",         // Auth with popup/redirect
  databaseURL: "https://YOUR_APP.firebaseio.com", // Realtime Database
  storageBucket: "YOUR_APP.appspot.com",          // Storage
  messagingSenderId: "123456789"                  // Cloud Messaging
});

```

## Example 2


```javascript

// Initialize another app
const otherApp = initializeApp({
  databaseURL: "https://<OTHER_DATABASE_NAME>.firebaseio.com",
  storageBucket: "<OTHER_STORAGE_BUCKET>.appspot.com"
}, "otherApp");

```