Arne Reimers, Software Engineer at Google Identity and Engagement. Julia Steier, Product Manager at Google Identity and Engagement. Cedric Strickland, Product Manager for Gmail. As of March 31, US users can now change their Google Account username without losing their account, inbox, or any of their data. If your platform supports Sign in with Google or identifies users by email address, this update may impact your integration and could require some action on your part.
Many people still use old email addresses that no longer represent who they are—due to a name change, career shift, or simply because they’ve outgrown the original username.
With this change, when a user updates their username, their original email address will be kept as an additional linked address on the same account. Both messages are directed to the identical inbox. Users can keep signing in, as well as sending and receiving emails, with either option. We’re now extending this feature—previously limited to business Workspace users—to personal Google Accounts using @gmail.com.
Google Developers Blog