D.6 Anonymous Auth

Authenticate with Firebase Anonymously

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 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. In the Firebase console, open the Auth section.
2. On the Sign-in Methods page, enable the Anonymous sign-in method.

When a signed-out user uses an app feature that requires authentication with Firebase, sign in the user anonymously like below:

Auth.listener.addEventListener(AuthEvents.SIGN_IN_RESULT, onSignInResult);
Auth.signIn(null); // instead of passing the login credential, just pass null

function onSignInResult(e:AuthEvents):void
{
	if(e.result == Auth.RESULT_SUCCESS)
	{
		trace("signed in successfully");
		
		/*
			When sign in is successful, the AUTH_STATE_CHANGED event will be dispatched which
			you can use to read user's information.
		*/
	}
	else
	{
		trace("onSignInResult: " + e.msg);
	}
}

:start: To protect your project from abuse, Firebase limits the number of new email/password and anonymous sign-ups that your application can have from the same IP address in a short period of time. You can request and schedule temporary changes to this quota from the Firebase console.

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 Auth.signInWith methods. For example, get the user's Google ID token, Facebook access token, or email address and password.
2. Get an authProvider.getCredential() for the new authentication provider:

var authProvider:AuthProvider = new AuthProvider();

// Google Sign-In
authProvider.setGoogleAuthProvider("id_token", "access_token");

// Facebook Login
authProvider.setFacebookAuthProvider("access_token");

// Email-password sign-in
authProvider.setEmailAuthProvider("email", "password");

// other auth providers...

Pass the authProvider.getCredential() object to the sign-in user's linkWithCredential method:

FirebaseUser.listener.addEventListener(FirebaseUserEvents.LINK_WITH_RESULT, onLink);
FirebaseUser.linkWithCredential(authProvider.getCredential());

function onLink(e:FirebaseUserEvents):void
{
	C.log("onLink result=" + e.result, "     msg=" + e.msg);
}

⭐ This technique can also be used to link any two accounts.