What is the difference between OpenID and SAML?

Question

What is the difference between OpenID and SAML?

Answer 1

Both SAML and OpenID can act as identity provider (abbreviated IdP) i.e. decentralized authentication protocol(single sign-on identity).

The Security Assertion Markup Language (SAML) is a set of profiles for exchanging authentication and authorization data across security domains. In the SAML domain model, an identity provider is a special type of authentication authority. Specifically, a SAML identity provider is a system entity that issues authentication assertions in conjunction with an SSO profile of SAML. A relying party that consumes these authentication assertions is called a SAML service provider. Source

OpenID Connect (OIDC) is an authentication layer on top of OAuth 2.0, an authorization framework. The standard is controlled by the OpenID Foundation. OAuth is for authorization protocol, rather than an authentication protocol and OpenID specifically designed as an authentication protocol. OIDC uses simple JSON Web Tokens (JWT), they are easier to consume by JavaScript.

Use case Scenario:

Use OAuth if your users might just want to login with Facebook, or Twitter. Use OpenID if your users are neckbeards that run their own OpenID providers because they "don't want anyone else owning their identity".

Source