Your app supports various types of user authentication. Where each type of authentication is used is based on the relationship of the user to your business and transaction. Google sign in After a user signs in for the first time using their Google account credentials, a new user account is created and linked to the credentials — that is, the user name and password, phone number, or auth provider information — the user signed in with. This new account is stored as part of your app data, and can be used to identify a user whilst using your app, regardless of how the user signs in. Email sign in Your app supports email authentication whereby to sign in a user by sending them an email containing a link, which they can click to sign in. In the process, the user’s email address is also verified. There are numerous benefits to signing in by email, especially low friction sign-up and sign-in. An existing user who previously signed in with an email identifier can be upgraded to sign in with just the email. For example, a user who has forgotten their password can still sign in without needing to reset their password. Lower risk of password reuse across app, which can undermine security of even well-selected passwords. Passwordless sign in Passwordless authentication is a type of authentication where users do not need to log in with passwords. With this form of authentication, users are presented with the options of either logging in simply via a magic link, fingerprint, or using a token that is delivered via email or text message. Anonymous sign in Users of your app are allowed to create and use temporary anonymous accounts to authenticate. 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 later to sign up to your app, we link their sign-in credentials to the anonymous account so that they can continue to work with their protected data in future sessions.