Introduction
Single Sign-on (SSO) is a technology that allows users to sign in only once and then get access to multiple applications/services without re-authentication.
If a web portal includes several large independent sections (forum, chat, blogs etc.), a user can undergo the authentication procedure within one of the services and automatically get access to all other services without entering credentials several times.
SSO is always ensured by the joint operation of two applications: an Identity Provider and a Service Provider (also called as "IdP" and "SP"). ONLYOFFICE SSO implements the SP only. A lot of different providers can act as an IdP, but this article considers the Active Directory Federation Services (AD FS) implementation.