Single Sign-On

Single sign-on, or SSO, is an authentication scheme that lets a user log in once and gain access to multiple separate software systems or websites without having to sign in again to each one individually. The approach grew out of enterprise computing during the 1980s and 1990s, as organizations sought to manage employee access across many internal systems from one central directory, and it became a mainstream consumer feature during the 2000s through services that let a user log into third-party websites with an existing account, such as an email or social-media provider. Single sign-on relies on a trusted identity provider that authenticates the user once and then vouches for that identity to each connected application; the source consulted for this entry names no single inventor or origin date for the technique as a whole, so none is recorded here.