[Home](./index.md) > [@firebase/auth](./auth.md) > [signInAnonymously](./auth.signinanonymously.md) ## signInAnonymously() function Asynchronously signs in as an anonymous user. Signature: ```typescript export declare function signInAnonymously(auth: Auth): Promise; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | auth | [Auth](./auth.auth.md) | The Auth instance. | Returns: Promise<[UserCredential](./auth.usercredential.md)> ## Remarks If there is already an anonymous user signed in, that user will be returned; otherwise, a new anonymous user identity will be created and returned.