Auth0 starts free for 7,500 MAUs. Then the Essential plan is $240/year for up to 1,000 MAUs. The Professional plan is $1,500/year. Need enterprise SSO (SAML, LDAP)? That's the Enterprise plan — "contact us" pricing that typically runs $3,000-10,000+/year.
Okta's pricing is similar or worse. Cognito charges $0.0055/MAU after the free tier — which sounds cheap until you're at 100,000 MAUs and paying $550/month for auth alone.
The pricing structure of authentication-as-a-service reflects the vendor lock-in risk: switching auth providers is genuinely hard, so they can charge what the market will bear as you scale.
Open source authentication tools solve the economics problem. Deploy once on your infrastructure, and your auth cost doesn't scale with user count — it scales with compute, which is much more linear. More importantly, you own the user data and the session infrastructure.
I compared 3 open source authentication platforms that are production-ready, actively maintained, and genuinely capable of replacing Auth0 or Okta for most use cases.
Key Takeaways:
- Best enterprise identity platform: ZITADEL — full OIDC/SAML provider with multi-tenancy, machine-to-machine auth, and robust compliance features
- Best developer-focused auth: Logto — modern CIAM with excellent DX, pre-built UI components, and growing enterprise features
- Best for Next.js/TypeScript apps: Better Auth — framework-first approach, TypeScript-native, drop-in solution for modern web apps
Quick Comparison
| Tool | Best For | Self-Hosted | SSO/SAML | MFA | Multi-Tenant | SDK |
|---|---|---|---|---|---|---|
| ZITADEL | Enterprise identity | Yes | Yes | Yes | Yes | All major languages |
| Logto | Developer CIAM | Yes | Yes (paid) | Yes | Yes | JS, Python, Go, more |
| Better Auth | Web app auth | Embedded | Partial | Yes | Yes | TypeScript/JS native |
What to Look For in Open Source Authentication
Authentication is one place where cutting corners is genuinely dangerous. Here's what separates production-ready auth from a prototype:
- Standards compliance — OAuth 2.0, OIDC, and SAML support ensures compatibility with every enterprise identity provider
- MFA support — TOTP, WebAuthn/passkeys, SMS backup
- Multi-tenancy — can you isolate customer organizations with separate user pools and SSO configs?
- Machine-to-machine auth — client credentials flow for service-to-service authentication
- Audit logging — who logged in, when, from where — required for compliance
- SDK quality — how much code do you write to integrate auth into your app?
- Security response — does the project have a responsible disclosure process and a security team?
1. ZITADEL — Enterprise-Grade Identity Provider
Best for companies that need a full enterprise identity platform: multi-tenant B2B auth, SAML federation, machine-to-machine tokens, and compliance-ready audit trails.
ZITADEL is the most feature-complete open source identity provider on this list. It's designed as a direct replacement for Auth0 or Okta — not just user login, but the full enterprise identity stack: multi-tenant organizations with isolated user pools, SAML and OIDC federation, machine-to-machine auth via client credentials, and granular role-based access control.
The multi-tenancy model is particularly strong for B2B SaaS products. Each customer organization gets its own isolated identity space, can configure their own SSO (SAML or OIDC), and can set their own MFA policies — without affecting other tenants.
Key Features
- Multi-tenant organizations — isolated user pools with per-org SSO and MFA policies
- OIDC and SAML 2.0 — both identity provider and service provider roles
- Machine-to-machine auth — service accounts with client credentials flow
- Passwordless — WebAuthn/FIDO2, passkeys, and magic links
- MFA — TOTP authenticator apps, U2F/WebAuthn, SMS (with provider integration)
- Customizable login UI — hosted or custom-built with ZITADEL's API
- Audit logging — tamper-evident event log for every auth action
- Actions — serverless-style event hooks for custom logic on login/registration
Pros
- Most complete enterprise feature set of any open source auth provider
- B2B multi-tenancy is first-class, not an afterthought
- ZITADEL Cloud provides managed hosting with self-host option
- Strong compliance posture (SOC 2 for cloud, all audit events logged)
Cons
- Steeper learning curve than Logto or Better Auth due to feature breadth
- Kubernetes deployment recommended for production (adds ops complexity)
- Advanced features require understanding of ZITADEL's organization model
Self-Hosting
Single binary or Docker/Kubernetes deployment. Requires CockroachDB or PostgreSQL. Kubernetes Helm chart available for production deployments. ZITADEL Cloud offers managed hosting with self-host migration path.
License: Apache 2.0
GitHub Stars: 9k+
View ZITADEL on Open Source Alternatives
2. Logto — Modern CIAM for Developers
Best for developer teams building consumer or B2B products who want modern auth with excellent developer experience, pre-built UI components, and clear upgrade path to enterprise features.
Logto positions itself as Customer Identity and Access Management (CIAM) rather than just authentication — the distinction being a focus on the user journey (onboarding, social login, profile management) alongside the security primitives.
The developer experience is genuinely strong. SDKs for JavaScript, TypeScript, React, Next.js, Python, Go, PHP, and more. Pre-built sign-in UI components that are customizable without rebuilding from scratch. A management API for every operation. The docs are clear, the setup is fast.
Key Features
- Pre-built sign-in UI — customizable without building from scratch
- Social login — Google, GitHub, Apple, Facebook, and 20+ providers out of the box
- SMS and email passwordless — OTP-based login with pluggable providers
- MFA — TOTP, WebAuthn, backup codes
- RBAC — role-based access control with permission scopes
- Organizations — multi-tenant B2B support (with per-org SSO in Enterprise tier)
- SDKs — JavaScript, TypeScript, React, Next.js, Vue, Python, Go, PHP, iOS, Android
Pros
- Best developer experience (DX) of any open source auth tool
- Pre-built UI components cut integration time significantly
- Social and passwordless login are first-class citizens
- Well-documented with clear quickstarts
Cons
- Some enterprise features (SAML SSO, advanced organizations) require paid cloud plan
- SAML SP/IdP support is more limited than ZITADEL
- Newer than Keycloak — less battle-tested at extreme enterprise scale
Self-Hosting
Docker Compose for development. Kubernetes Helm chart for production. Requires PostgreSQL. Logto Cloud provides managed hosting. Self-hosted version is free and fully functional.
License: MPL 2.0 (core) / Apache 2.0 (some components)
GitHub Stars: 9k+
View Logto on Open Source Alternatives
3. Better Auth — TypeScript-First Web App Auth
Best for Next.js, Remix, or SvelteKit developers who want drop-in auth that integrates directly into their framework without running a separate auth service.
Better Auth takes a fundamentally different approach from ZITADEL and Logto. Rather than being a standalone identity provider, it's a library you embed in your Next.js or TypeScript backend. Auth runs inside your application, using your database, without a separate auth service to deploy and maintain.
The result is the lowest-friction auth integration for TypeScript web apps. Add the library, configure your database adapter (Drizzle, Prisma, Mongoose), and you get email/password, social login, sessions, MFA, organizations, and more — all type-safe and colocated with your application code.
Key Features
- Framework-native — integrates directly into Next.js, Remix, SvelteKit, Express
- TypeScript-first — fully typed with automatic type inference for plugins
- Plugin architecture — official plugins for 2FA, magic links, passkeys, organizations, RBAC
- Multiple database adapters — Drizzle, Prisma, Mongoose, and more
- Social providers — Google, GitHub, Discord, Twitch, and 30+ more
- Session management — cookie or JWT-based sessions with configurable TTL
- Admin panel — manage users, sessions, and organizations via built-in UI
Pros
- Zero separate auth service to deploy — runs inside your application
- Best TypeScript type safety of any auth solution
- Plugin system covers enterprise features (orgs, RBAC, 2FA) without bloat
- Very active development with frequent releases
Cons
- Not suitable for multi-application SSO (it's app-level auth, not a standalone IdP)
- Less battle-tested than ZITADEL for large-scale enterprise deployments
- SAML support limited — primarily for OIDC-based federation
- Still maturing — some plugins are newer and less tested
Self-Hosting
Runs inside your application — no separate deployment. Your existing app server and database are sufficient. Add the npm package and configure database adapter.
License: MIT
GitHub Stars: 10k+
View Better Auth on Open Source Alternatives
Which Auth Tool Is Right for You?
| Use Case | Best Choice |
|---|---|
| B2B SaaS with enterprise SSO requirements | ZITADEL |
| Consumer app with social login and smooth onboarding | Logto |
| Next.js/TypeScript app needing drop-in auth | Better Auth |
| Multi-tenant with per-customer SSO | ZITADEL |
| Developer-focused product wanting fast setup | Logto |
| Service-to-service / machine-to-machine auth | ZITADEL |
Self-Hosting Considerations for Auth
Authentication is a high-availability requirement — if your auth service is down, no one can log in. Plan for this:
- Run at least 2 replicas for any production auth service
- Database backup — auth data (users, sessions, credentials) must be backed up regularly
- SSL termination — auth endpoints must be HTTPS, no exceptions
- Session secret rotation — have a process for rotating secrets without logging everyone out
- Monitoring — alert on auth service uptime and failed login rate anomalies
ZITADEL and Logto both support horizontal scaling via their Kubernetes deployments. Better Auth scales with your application server.
Frequently Asked Questions
What's the best Auth0 alternative for self-hosting?
ZITADEL is the most direct Auth0 replacement with comparable feature breadth — multi-tenancy, SAML, OIDC, machine-to-machine, and enterprise SSO. Logto is better for consumer-facing CIAM with a focus on user experience.
Can I migrate users from Auth0 to an open source alternative?
Yes, but it requires careful planning. Passwords can't be migrated directly (Auth0 stores them hashed), but you can migrate user records and trigger password resets on first login. Session-based migration is complex — plan for a dual-running period.
Is it safe to self-host authentication?
Self-hosted auth is as secure as you make it. ZITADEL and Logto are used in production by companies that handle sensitive data. The key requirements: HTTPS everywhere, regular security updates, proper database backup, and monitoring for anomalous login patterns.
Do these tools support passkeys and WebAuthn?
Yes — ZITADEL supports WebAuthn/FIDO2 natively. Logto supports WebAuthn. Better Auth has a passkeys plugin. All three support the modern passwordless authentication standards.
How does multi-tenancy work for B2B SaaS?
ZITADEL's organization model is purpose-built for B2B: each customer gets an isolated "organization" with its own user pool, SSO configuration, and MFA policy. Logto also supports organizations. Better Auth has an organizations plugin for team-level isolation.
What's the difference between an IdP and an auth library?
An Identity Provider (IdP) like ZITADEL or Logto is a standalone service — it runs separately from your app and issues tokens that your app validates. An auth library like Better Auth runs inside your app, directly managing sessions and credentials. IdPs are better for multi-app environments; libraries are better for single-app architectures.
Do these support SCIM for directory sync?
ZITADEL has SCIM support. Logto is working on it. Better Auth focuses on application-level auth rather than enterprise directory sync. For SCIM requirements, ZITADEL is the right choice.
What's the compliance story for self-hosted auth?
Self-hosting means you control the data, which simplifies some compliance requirements (data residency, sovereignty). However, you're responsible for your own audit trail, access controls, and breach response. All three tools provide audit logging. ZITADEL's Cloud offering has SOC 2 certification.