The alternatives
keycloak
Open Source Identity and Access Management For Modern Applications and Services
keycloak/keycloak Updated 2026-05-06 authelia
The Single Sign-On Multi-Factor portal for web apps, now OpenID Certified™
authelia/authelia Updated 2026-05-05 authentik
The authentication glue you need.
goauthentik/authentik Updated 2026-05-06 supertokens-core
Open source alternative to Auth0 / Firebase Auth / AWS Cognito
supertokens/supertokens-core Updated 2026-05-05 zitadel
ZITADEL - Identity infrastructure, simplified for you.
zitadel/zitadel Updated 2026-05-06 kratos
Headless cloud-native authentication and identity management written in Go. Scales to a billion+ users. Replace Homegrown, Auth0, Okta, Firebase with better UX and DX. Passkeys, Social Sign In, OIDC, Magic Link, Multi-Factor Auth, SMS, SAML, TOTP, and more. Runs everywhere, runs best on Ory Network.
ory/kratos Updated 2026-05-05 Comparison notes
Keycloak is the most feature-complete OSS identity provider, covering OIDC, SAML, social login, MFA, and fine-grained authorization. It matches or exceeds Auth0 on protocol support. The gaps: Keycloak is a Java application with significant operational overhead — JVM tuning, clustering for HA, and a steep learning curve on its admin console. Auth0's Actions (JavaScript hooks for login flows), its anomaly detection, and its breached password detection have no direct Keycloak equivalent. Logto and Casdoor are lighter alternatives targeting developer-friendliness, but their enterprise feature maturity lags. Self-hosting auth is higher risk than most infrastructure choices — factor in incident response capability.
Migration tips
- Export Auth0 user data via the Management API (/api/v2/users) in JSON or CSV; passwords are hashed and cannot be exported — plan for password reset on first login
- Map your Auth0 tenant's social connections to Keycloak's identity provider configuration one by one
- Audit Auth0 Rules and Actions (pre-migration hooks, post-login logic) and rewrite them as Keycloak event listeners or script authenticators
- Test MFA enrollment flows with a pilot group before migration — TOTP secrets are not transferable between platforms
- Update all application OIDC configurations (client_id, redirect_uri, discovery endpoint) and test token validation in each service
FAQ
Can I fully replace Auth0 with an OSS tool?
Feature parity varies. Most OSS alternatives cover 70-90% of core workflows, but may lack polish, integrations, or specialized features. Pilot the alternative with a subset of your team before fully committing.
What's the cost of self-hosting?
Plan for ~$5-50/month in VPS costs (DigitalOcean, Hetzner, etc.) plus 2-8 hours/month in maintenance. For a team of 20+, self-hosting usually breaks even against SaaS pricing within 6-12 months.
Which alternative should I pick?
Sort by GitHub stars (a proxy for community health), check the last-pushed date (avoid unmaintained projects), and read recent issues to gauge responsiveness.