What is the difference between Federated Login and Single Sign On?

Single Sign-on (SSO) allows users to access multiple services with a single login.

The term is actually a little ambiguous. Sometimes it's used to mean that (1) the user only has to provide credentials a single time per session, and then gains access to multiple services without having to sign in again during that session. But sometimes it's used to mean (2) merely that the same credentials are used for multiple services; the user might have to login multiple times, but it's always the same credentials. So beware, all SSO's are not the same in that regard. Many people (me included) only consider the first case to be "true" SSO.

Federated Identity (FID) refers to where the user stores their credentials. Alternatively, FID can be viewed as a way to connect Identity Management systems together. In FID, a user's credentials are always stored with the "home" organization (the "identity provider"). When the user logs into a service, instead of providing credentials to the service provider, the service provider trusts the identity provider to validate the credentials. So the user never provides credentials directly to anybody but the identity provider.

FID and SSO are different, but are very often used together. Most FID systems provide some kind of SSO. And many SSO systems are implemented under-the-hood as FID. But they don't have to be done that way; FID and SSO can be completely separate too.

SSO allows a single authentication credential--user ID and password, smart card, one-time password token or a biometric device--to access multiple or different systems within a single organization. A federated identity management system provides single access to multiple systems across different enterprises.

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Web SSO , can be defined as "you need to enter your credential once and is they are under same cookie provider , you dont need to re enter the username and password if they are also under same cookie provider" eg: Gmail-->google

Federated SSO can be defined as "you may be asked to use an application which is under different enterprise/network or say an other organisation , at this case we need to have Federation , where if you want to use the service of another firms web product eg service now then you will serve as the Identity provider[IDP] and they will be the service Provider[SP]"