veritatisdoloremque/docs-exp/auth-types.auth.md

Monorepo for the Firebase JavaScript SDK

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[Home](./index.md) &gt; [@firebase/auth-types](./auth-types.md) &gt; [Auth](./auth-types.auth.md)

## Auth interface

Interface representing Firebase Auth service.

<b>Signature:</b>

```typescript
export interface Auth 
```

## Remarks

See [Firebase Authentication](https://firebase.google.com/docs/auth/) for a full guide on how to use the Firebase Auth service.

## Properties

|  Property | Type | Description |
|  --- | --- | --- |
|  [config](./auth-types.auth.config.md) | [Config](./auth-types.config.md) | The [Config](./auth-types.config.md) used to initialize this instance. |
|  [currentUser](./auth-types.auth.currentuser.md) | [User](./auth-types.user.md) \| null | The currently signed-in user (or null). |
|  [languageCode](./auth-types.auth.languagecode.md) | string \| null | The Auth instance's language code. |
|  [name](./auth-types.auth.name.md) | string | The name of the app associated with the Auth service instance. |
|  [settings](./auth-types.auth.settings.md) | [AuthSettings](./auth-types.authsettings.md) | The Auth instance's settings. |
|  [tenantId](./auth-types.auth.tenantid.md) | string \| null | The Auth instance's tenant ID. |

## Methods

|  Method | Description |
|  --- | --- |
|  [onAuthStateChanged(nextOrObserver, error, completed)](./auth-types.auth.onauthstatechanged.md) | Adds an observer for changes to the user's sign-in state. |
|  [onIdTokenChanged(nextOrObserver, error, completed)](./auth-types.auth.onidtokenchanged.md) | Adds an observer for changes to the signed-in user's ID token. |
|  [setPersistence(persistence)](./auth-types.auth.setpersistence.md) | Changes the type of persistence on the Auth instance. |
|  [signOut()](./auth-types.auth.signout.md) | Signs out the current user. |
|  [updateCurrentUser(user)](./auth-types.auth.updatecurrentuser.md) | Asynchronously sets the provided user as [Auth.currentUser](./auth-types.auth.currentuser.md) on the [Auth](./auth-types.auth.md) instance. |
|  [useDeviceLanguage()](./auth-types.auth.usedevicelanguage.md) | Sets the current language to the default device/browser preference. |
|  [useEmulator(url, options)](./auth-types.auth.useemulator.md) | Modify this Auth instance to communicate with the Firebase Auth emulator. |