What is an identity provider?

An identity provider, or IdP for short, is a system responsible for user authentication. It stores accounts and passwords, verifies that the user is who they claim to be, and in return issues a token - a signed confirmation of identity. The store, mobile app, or business dashboard does not store passwords; instead, it verifies the token. Data exchange is handled using standards, most commonly OpenID Connect (OIDC) and SAML.

You can host the identity provider yourself - for example, using Keycloak on your own server - or purchase it as a service, such as Auth0. It is the heart of Single Sign-On: thanks to it, a single account works across multiple channels. The security of the entire system depends on whether applications fully validate the token - that is, its signature, validity, and the entity for which it was issued.