Authenticate with Firebase Anonymously on Apple Platforms

You can use Firebase Authentication to create and use temporary anonymous accounts to authenticate with Firebase. These temporary anonymous accounts can be used to allow users who haven't yet signed up to your app to work with data protected by security rules. If an anonymous user decides to sign up to your app, you can link their sign-in credentials to the anonymous account so that they can continue to work with their protected data in future sessions.

Before you begin

  1. Use Swift Package Manager to install and manage Firebase dependencies.

    1. In Xcode, with your app project open, navigate to File > Add Packages.
    2. When prompted, add the Firebase Apple platforms SDK repository:
      3.   https://github.com/firebase/firebase-ios-sdk.git
    3. Choose the Firebase Authentication library.
    4. Add the -ObjC flag to the Other Linker Flags section of your target's build settings.
    5. When finished, Xcode will automatically begin resolving and downloading your dependencies in the background.
  2. If you haven't yet connected your app to your Firebase project, do so from the Firebase console.
  3. Enable anonymous auth:
    1. In the Firebase console, open the Auth section.
    2. On the Sign-in Methods page, enable the Anonymous sign-in method.
    3. Optional: If you've upgraded your project to Firebase Authentication with Identity Platform, you can enable automatic clean-up. When you enable this setting, anonymous accounts older than 30 days will be automatically deleted. In projects with automatic clean-up enabled, anonymous authentication will no longer count toward usage limits or billing quotas. See Automatic clean-up.

Authenticate with Firebase anonymously

When a signed-out user uses an app feature that requires authentication with Firebase, sign in the user anonymously by completing the following steps:

  1. Import the FirebaseCore module in your UIApplicationDelegate, as well as any other Firebase modules your app delegate uses. For example, to use Cloud Firestore and Authentication:

    SwiftUI

    import SwiftUI
import FirebaseCore
import FirebaseFirestore
import FirebaseAuth
// ...

    Swift

    import FirebaseCore
import FirebaseFirestore
import FirebaseAuth
// ...

    Objective-C

    @import FirebaseCore;
@import FirebaseFirestore;
@import FirebaseAuth;
// ...
  2. Configure a FirebaseApp shared instance in your app delegate's application(_:didFinishLaunchingWithOptions:) method:

    SwiftUI

    // Use Firebase library to configure APIs
FirebaseApp.configure()

    Swift

    // Use Firebase library to configure APIs
FirebaseApp.configure()

    Objective-C

    // Use Firebase library to configure APIs
[FIRApp configure];
  3. If you're using SwiftUI, you must create an application delegate and attach it to your App struct via UIApplicationDelegateAdaptor or NSApplicationDelegateAdaptor. You must also disable app delegate swizzling. For more information, see the SwiftUI instructions.

    SwiftUI

    @main
struct YourApp: App {
  // register app delegate for Firebase setup
  @UIApplicationDelegateAdaptor(AppDelegate.self) var delegate

  var body: some Scene {
    WindowGroup {
      NavigationView {
        ContentView()
      }
    }
  }
}
  4. Call the signInAnonymouslyWithCompletion: method:

    Swift

    Auth.auth().signInAnonymously { authResult, error in
  // ...
}

    Objective-C

    [[FIRAuth auth] signInAnonymouslyWithCompletion:^(FIRAuthDataResult * _Nullable authResult,
                                                  NSError * _Nullable error) {
   // ...
 }];
  5. If the signInAnonymouslyWithCompletion: method completes without error, you can get the anonymous user's account data from the FIRAuthDataResult object:

    Swift

    guard let user = authResult?.user else { return }
let isAnonymous = user.isAnonymous  // true
let uid = user.uid

    Objective-C

    FIRUser *user = authResult.user;
BOOL isAnonymous = user.anonymous;  // YES
NSString *uid = user.uid;

Convert an anonymous account to a permanent account

When an anonymous user signs up to your app, you might want to allow them to continue their work with their new account—for example, you might want to make the items the user added to their shopping cart before they signed up available in their new account's shopping cart. To do so, complete the following steps:

  1. When the user signs up, complete the sign-in flow for the user's authentication provider up to, but not including, calling one of the FIRAuth.signInWith methods. For example, get the user's Google ID token, Facebook access token, or email address and password.

  2. Get an FIRAuthCredential for the new authentication provider:

    Google Sign-In
    Swift
    guard
  let authentication = user?.authentication,
  let idToken = authentication.idToken
else {
  return
}

let credential = GoogleAuthProvider.credential(withIDToken: idToken,
                                               accessToken: authentication.accessToken)
    Objective-C
    FIRAuthCredential *credential =
[FIRGoogleAuthProvider credentialWithIDToken:result.user.idToken.tokenString
                                 accessToken:result.user.accessToken.tokenString];
    Facebook Login
    Swift
    let credential = FacebookAuthProvider
  .credential(withAccessToken: AccessToken.current!.tokenString)
    Objective-C
    FIRAuthCredential *credential = [FIRFacebookAuthProvider
    credentialWithAccessToken:[FBSDKAccessToken currentAccessToken].tokenString];
    Email-password sign-in
    Swift
    let credential = EmailAuthProvider.credential(withEmail: email, password: password)
    Objective-C
    FIRAuthCredential *credential =
    [FIREmailAuthProvider credentialWithEmail:email
                                             password:password];

  3. Pass the FIRAuthCredential object to the sign-in user's linkWithCredential:completion: method:

    Swift
        user.link(with: credential) { authResult, error in
  // ...
}
}
    Objective-C
        [[FIRAuth auth].currentUser linkWithCredential:credential
    completion:^(FIRAuthDataResult *result, NSError *_Nullable error) {
  // ...
}];

If the call to linkWithCredential:completion: succeeds, the user's new account can access the anonymous account's Firebase data.

Automatic clean-up

If you've upgraded your project to Firebase Authentication with Identity Platform, you can enable automatic clean-up in the Firebase console. When you enable this feature you allow Firebase to automatically delete anonymous accounts older than 30 days. In projects with automatic clean-up enabled, anonymous authentication will not count toward usage limits or billing quotas.

  • Any anonymous accounts created after enabling automatic clean-up might be automatically deleted any time after 30 days post-creation.
  • Existing anonymous accounts will be eligible for automatic deletion 30 days after enabling automatic clean-up.
  • If you turn automatic clean-up off, any anonymous accounts scheduled to be deleted will remain scheduled to be deleted.
  • If you "upgrade" an anonymous account by linking it to any sign-in method, the account will not get automatically deleted.

If you want to see how many users will be affected before you enable this feature, and you've upgraded your project to Firebase Authentication with Identity Platform, you can filter by is_anon in Cloud Logging.

Next steps

Now that users can authenticate with Firebase, you can control their access to data in your Firebase database using Firebase rules.