Keycloak

Keycloak is a battle-tested, open-source Identity and Access Management (IAM) solution maintained by Red Hat. It provides single sign-on (SSO), social login, user federation, and fine-grained authorisation out of the box — with support for standard protocols including OAuth 2.0, OpenID Connect (OIDC), and SAML 2.0.

Deployed as a standalone server, Keycloak manages users, roles, and client applications through a rich admin console. It supports external identity providers, LDAP/Active Directory federation, custom authentication flows, and multi-factor authentication — covering the full spectrum of enterprise identity needs.

Compared to Auth0 or Okta, Keycloak is entirely self-hosted and free, with no per-user pricing or usage caps. It is widely used in enterprises, cloud-native environments, and Kubernetes clusters (via the Keycloak Operator), making it the go-to open-source choice for organisations that want full control over their identity infrastructure.