Supporting Google Account username change in your app

Google now allows US users to update their Google Account username while retaining their original email as an alias, and this post explains the integration impact for platforms using Sign in with Google.

• •If your platform uses subject ID (sub) as the primary user identifier, no action is needed as it remains stable after a username change.
• •If your platform identifies users by email address from the ID token, users may face duplicate accounts or loss of access when an OAuth grant is revoked and a new email is issued.
• •Manual email/password users are unaffected for sign-in, but risk duplicate accounts if they later use Sign in with Google with a new email address.
• •Google recommends migrating to subject ID as the primary identifier, offering email-based account recovery, and allowing users to update their email in platform settings.