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Zitadel
AGPL-3.0Open-source identity platform with native B2B multi-tenancy, Passkeys, event-sourced audit trails, and typed gRPC and REST APIs to replace Auth0.
Open-source alternative to — compare it against:
Overview
Swiss engineering firm CAOS AG created Zitadel in 2020 because existing identity platforms either required heavy runtimes or locked multi-tenant application data into proprietary cloud vendors. The founders built the system around a single Go binary and an event-sourced audit log to give software teams authentication they could run on their own infrastructure. Today, that origin gives developers full data ownership, zero-downtime updates, and European data sovereignty.
Why Zitadel instead of Auth0
Auth0 structures integration around REST APIs, specialized runtime sandboxes, and commercial tiers where SAML federation and identity brokering carry separate add-on fees. Zitadel approaches integration from an API-first stance, exposing typed gRPC, connectRPC, and REST interfaces across every resource. Instead of treating audit trails as secondary log exports, Zitadel writes every mutation into an immutable event stream, allowing engineering teams to subscribe to lifecycle events or stream authentication activity directly into external SIEM pipelines.
Where Auth0 limits multi-tenancy unless teams purchase enterprise plans or juggle isolated tenant accounts, Zitadel includes an organization and project hierarchy out of the box. Business customers can self-service integrate corporate SAML 2.0 or OpenID Connect identity providers and map roles through project grants without per-connection fees. Switching from Auth0 requires operational ownership: instead of relying on a managed cloud dashboard, DevOps engineers maintain a PostgreSQL cluster and translate custom authentication scripts into Zitadel webhook actions and token enrichment hooks.
What it does well
- Typed gRPC and connectRPC APIs alongside standard REST endpoints let backend developers generate client SDKs and automate tenant provisioning in CI/CD pipelines.
- Event-sourced architecture records every mutation into an immutable store, delivering audit trails and webhook feeds for compliance without external logging agents.
- Built-in multi-tenancy provides organizations, project grants, and self-service identity brokering, letting enterprise clients configure corporate SAML or OpenID Connect providers independently.
- Passwordless authentication and FIDO2 WebAuthn Passkeys come enabled across all tiers, eliminating commercial upcharges for biometric logins.
- Stateless application instances scale horizontally behind a reverse proxy, requiring only a shared PostgreSQL database without separate session stores for clustering.
