One or more web applications are configured to use Windows Classic authentication (SharePoint Server)
APPLIES TO: 
2013 2016 2019 Subscription Edition 
SharePoint in Microsoft 365
Rule Name: One or more web applications are configured to use Windows Classic authentication.
Summary: This health rule is triggered when at least one Web application is configured to use Windows Classic authentication mode. Windows Classic authentication is deprecated in SharePoint Server. We recommend that you migrate to claims-based authentication, because many of the features in SharePoint Server require the claims-based authentication mode.
Cause: Web applications are configured to use Windows Classic authentication mode.
Resolution: Migrate Web applications from classic mode to claims-based authentication.
- You have to migrate Web applications from classic mode to claims-based authentication. For more information, see Migrate from classic-mode to claims-based authentication in SharePoint Server.