Federated Identity or Identity Federation

Identity Federation is a series of applications and techniques to enable user identities to be linked across multiple separate user directories.

For example, within an organization, user accounts for employees based in one city and user accounts for employees based in another city, stored in separate databases, may be federated so that users from either city can log in when in either office.

Federated identity platforms are often used to achieve single sign-on capability (SSO), which links user accounts not just within a single organization, but across accounts at multiple organizations or applications, to enable users to access many secure platforms without having to repeatedly authenticate.