[Home](./index.md) > [@firebase/auth](./auth.md) > [initializeAuth](./auth.initializeauth.md) ## initializeAuth() function Initializes an Auth instance with fine-grained control over [Dependencies](./auth.dependencies.md). Signature: ```typescript export declare function initializeAuth(app: FirebaseApp, deps?: Dependencies): Auth; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | app | [FirebaseApp](./app.firebaseapp.md) | | | deps | [Dependencies](./auth.dependencies.md) | | Returns: [Auth](./auth.auth.md) ## Remarks This function allows more control over the Auth instance than [getAuth()](./auth.getauth.md). `getAuth` uses platform-specific defaults to supply the [Dependencies](./auth.dependencies.md). In general, `getAuth` is the easiest way to initialize Auth and works for most use cases. Use `initializeAuth` if you need control over which persistence layer is used, or to minimize bundle size if you're not using either `signInWithPopup` or `signInWithRedirect`. For example, if your app only uses anonymous accounts and you only want accounts saved for the current session, initialize Auth with: ```js const auth = initializeAuth(app, { persistence: browserSessionPersistence, popupRedirectResolver: undefined, }); ```