Keycloak — #1 Alternative to Auth0
CNCF graduated enterprise open-source IAM for OIDC, OAuth 2.0, and SAML 2.0
Battle-tested identity server supporting multi-realm B2B tenancy, LDAP/Active Directory federation, WebAuthn passkeys, and custom theme templates with zero MAU fees.
License: Apache-2.0 · Pricing: Free & Open Source · Compare all Auth0 alternatives · Official Website