Definition
Single sign-on SSO is an authentication scheme that allows a user to log in with a single set of credentials to access multiple independent software systems. Instead of remembering and entering different usernames and passwords for each application, users are granted access to all authorized services after completing one authentication process. This is typically achieved through a trusted identity provider that issues security tokens after the initial successful login. SSO significantly enhances user experience and productivity by reducing login friction and streamlining access to necessary tools. For example, an employee might use their company network login to access their email, HR portal, and project management software without re-authenticating. It is important to distinguish SSO from multi-factor authentication MFA, which is a security process that requires multiple forms of verification, though SSO often incorporates MFA for stronger security. SSO is a key concept tested on certifications like CompTIA Security+ and the CISSP.