ZITADEL — #4 Alternative to Auth0
Single-binary Go multi-tenant B2B identity infrastructure built on Postgres
Purpose-built for B2B SaaS multi-tenancy with unlimited customer organizations, SAML/OIDC federation, audit event sourcing, and first-class passkey UX.
License: Apache-2.0 · Pricing: Open Core · Compare all Auth0 alternatives · Official Website