Single sign-on (SSO) is a session and user authentication service that permits a user to use one set of login credentials (e.g., name and password) to access multiple applications. SSO can be used by enterprises, smaller organizations, and individuals to mitigate the management of various usernames and passwords.  

In a basic web SSO service, an agent module on the application server retrieves the specific authentication credentials for an individual user from a dedicated SSO policy server, while authenticating the user against a user repository such as a lightweight directory access protocol (LDAP) directory. The service authenticates the end user for all the applications the user has been given rights to and eliminates future password prompts for individual applications during the same session.

User requests access

User is granted access and then requests access to a new site