Auth0 Alternatives: 6 Options Compared (Including Open Source)

You picked Auth0 when login was the thing standing between you and a shipped product. If the thing standing between you and your product now is the Auth0 invoice, or the tier wall in front of a feature you suddenly need, this comparison is for you. Six Auth0 alternatives, what each one does better than Auth0, where it hurts, and pricing that comes from each vendor's own pricing page in September 2026.

TL;DR: which Auth0 alternative should you pick?

Details on each below, with the tradeoffs spelled out.

Why teams start looking for Auth0 alternatives

The free tier is fine. Up to 25,000 monthly active users, social login, passkeys, one custom domain. The problem arrives with the paid tiers, and it arrives from two directions at once.

The B2B ladder is steep. Auth0 Essentials starts at $150/month for 500 MAUs and hits $2,100/month at 30,000 MAUs. Professional starts at $800/month. Enterprise connections (SAML, AD, LDAP) cost $100/month each beyond the three included on Essentials.

The B2C ladder looks cheaper, $35/month at the bottom, until you read the feature table. Role management is not on Free or Essentials. Custom database connections need Professional. Log retention is 1 day on Free, 5 on Essentials. If your app needs roles, and business apps need roles, you are on Professional at $240/month before your first overage.

That structure works for companies whose auth bill is a rounding error. It pinches everyone else.

Clerk

Clerk is the closest thing to Auth0's developer experience at a startup-friendly price. Prebuilt React/Next.js components for sign-in, sign-up, and user profiles, plus APIs behind them.

Where it beats Auth0: price and included features. Pro is $25/month with 50,000 monthly retained users included, MFA, and one enterprise connection (SAML/OIDC) included, where Auth0's Professional tier starts at $240/month. Clerk's MRU billing only counts users who return at least a day after signup, so churned signups don't bill.

Where it hurts: passkeys, custom password requirements, and MFA are all Pro features. The session lifetime is fixed at 7 days on the free tier. And Clerk is a hosted service; there is no self-hosted escape hatch.

Best for: React-based SaaS products that want polished auth UI without designing it.

Supabase Auth

Supabase is a Postgres platform with auth built in, and for a lot of teams that adjacency is the whole argument. Users live in your database. Row Level Security ties authorization to the same connection.

Where it beats Auth0: 50,000 MAU on the free tier, 100,000 included on the $25/month Pro tier, then $0.00325 per MAU. A quarter million MAUs on Supabase Auth costs roughly $488/month in overages plus the Pro plan. Auth0's B2C Essentials table tops out at $3,500/month for 50,000 MAUs, with custom quotes beyond that. SAML SSO is metered at $0.015 per MAU past 50 included, so a handful of enterprise customers costs dollars where Auth0 charges $100/month per connection.

Where it hurts: it is part of a bigger machine. You are buying a Postgres platform, and auth-heavy uses that don't want Postgres get no benefit from the bundling. Free-tier projects pause after a week of inactivity. Advanced phone MFA is an add-on at $75/month.

Best for: teams whose app is already (or about to be) built on Postgres.

Firebase Authentication / Identity Platform

Google's offering. Firebase Auth covers email, social, and phone sign-in for consumer apps; the underlying Identity Platform adds OIDC/SAML federation and multi-tenancy.

Where it beats Auth0: the free tier. 50,000 MAU free for tier-1 providers (email, social, phone, anonymous), then $0.0055 per MAU. A consumer app with a million monthly active users pays in the low thousands per month, usage-based, on Google infrastructure.

Where it hurts: federation is priced by a different meter. OIDC and SAML users cost $0.015 per MAU with only 50 free. An enterprise SaaS with 75,000 federated users pays about $1,125/month for federation alone. And you should assume some level of Google Cloud lock-in with the rest of the stack.

Best for: consumer apps, mobile apps, anything already living in the Google ecosystem.

Keycloak

The default answer to "open source Auth0 alternative." A CNCF incubating project, around since 2014, with an admin console, SSO, social login, user federation to LDAP and Active Directory, and fine-grained authorization policies. Current release line: 26.x.

Where it beats Auth0: it is free, self-hosted, and supports SAML natively, which Auth0 meters per connection. No MAU counting, no tier walls, no invoice at all beyond the server it runs on.

Where it hurts: you run it. Upgrades, clustering, backups, uptime, and the security patch cadence are your job. The admin console and theming story take more effort than any hosted option. And Keycloak is an identity server, full stop; the users, roles, and sessions it manages still need an application platform around them to do anything.

Best for: teams with ops capacity, strict data-residency rules, or tight budgets.

Ory

An open source identity stack (Kratos for identity, Hydra for OAuth2, Keto for permissions, Ory Network as the hosted version) with API-first architecture and a security-research pedigree. Ory's own materials note Hydra powers OpenAI's OAuth2 infrastructure.

Where it beats Auth0: headless, API-first design where you own the entire login UX. Open source components you can walk away with. A self-hosting path (Ory Enterprise License) that Auth0 only offers as an Enterprise add-on.

Where it hurts: the cloud pricing starts higher than it looks. Production is $770/year, and B2B organizations only arrive on Growth at $9,350/year, capped at 3 organizations. Build-your-own UI means frontend work before the first user signs in.

Best for: teams that want to own the login experience end to end, and enterprises with compliance requirements.

Zitadel

A newer open source entry from Switzerland, with a cloud plan and a self-hostable core. Multi-tenancy and audit logging were designed in from the start.

Where it beats Auth0: the free tier includes unlimited users and unlimited organizations with 100 daily active users, and its data-residency options (EU, US, Switzerland, Australia) are on the free tier. Pro is $100/month with 25,000 daily active users included. Self-hosting gets first-class support.

Where it hurts: a smaller ecosystem than Keycloak and less brand history than Auth0. The "Zitadel Next" alpha means some current attention is going into a rewrite. Pro includes 3 identity providers; beyond that, you are in enterprise conversations.

Best for: EU-centric companies and multi-tenant SaaS that wants organizations as a first-class concept.

Blocks OS (IAM)

Blocks OS belongs to a different category from the rest of this list: an application platform where identity is one of ten services. Blocks IAM handles sign-in and sign-up including social providers and GitHub SSO, OIDC flows and client management, sessions and devices, MFA including TOTP with backup codes, and the user/organization/role/permission model the rest of the platform consumes. It runs as an ASP.NET Core API with a React admin app, and it implements RFC 8693 token exchange so background workers can redeem a delegation grant carrying the originating user's tenant and organization context, with roles re-resolved at mint time.

Where it beats Auth0: it comes with the rest of the platform. The Data service generates CRUD and GraphQL APIs from schema definitions. The Logic service handles workflows. Release handles CI/CD, Monitor handles observability, Localization handles translations with AI-assisted suggestions. And the whole stack self-hosts as a Docker Compose setup (MongoDB, Redis, RabbitMQ, and the ten service pairs) on infrastructure you control, with automatic Let's Encrypt provisioning on the edge proxy. With Auth0, your identity provider is one more SaaS dependency; with Blocks, identity is part of the system you can run yourself. For a longer treatment of that difference, see Vercel vs Blocks OS.

Where it hurts: Blocks IAM comes as part of a platform, so you are evaluating Blocks OS rather than picking a login provider off a shelf. The free tier is enough to build and test against, and the platform bundles what a growing app needs anyway: data APIs, workflows, release pipelines, monitoring. The trade is scope. A team that wants only identity for a single app gets nine more services in the box, and scaling past the free tier is a conversation with SELISE rather than a checkout button.

Best for: teams building multi-tenant business software who want identity, data, and workflows as platform services on their own infrastructure.

Comparison table

Pricing in this table comes from each vendor's public pricing page as of September 2026 (Auth0, Clerk, Supabase, Google, Keycloak, Ory, Zitadel, linked above) and changes often; check the source pages before you commit.

When none of these are right

Three honest cases where this whole list fails you.

You need Auth0's specific ecosystem. Actions marketplace, extensive integration library, a decade of third-party content. If your stack already runs on Auth0 Actions and a migration costs more than the invoice, staying can be rational.

You need enterprise features at consumer pricing. Adaptive MFA, bot detection, and private deployment sit on Auth0's Enterprise tier. Every alternative above either lacks them, gates them behind their own enterprise tier (Ory, Zitadel cloud), or requires building them yourself (Keycloak). That is the honest cost of leaving.

You have no ops capacity and hard self-hosting requirements simultaneously. Keycloak, Ory, and Zitadel assume someone keeps the lights on. If the honest answer is that nobody on your team owns infrastructure, a hosted provider (any of them) beats a self-hosted identity server you cannot patch at 2 a.m.

FAQ

Is there a free Auth0 alternative? Blocks IAM, Keycloak and Zitadel are open source and free to self-host with few user limits. Hosted free tiers: Clerk and Supabase Auth at 50,000 users, Firebase at 50,000 MAU, Auth0 itself at 25,000 MAU.

What is the cheapest Auth0 alternative for SaaS? If you need something to start for free and then adopt the enterprise solutions, Blocks could be a great option. Supabase Auth on the $25/month Pro plan if you are on Postgres, or Clerk Pro at $25/month if you want prebuilt UI. Both include an order of magnitude more users at that price than Auth0's $35/month Essentials tier.

Can I self-host my identity provider instead of Auth0? Yes. Keycloak, Ory, and Zitadel, Blocks are the established open source options, and Supabase can be self-hosted via Docker. Blocks OS self-hosts as a full platform including IAM. Factor in the ops cost: patching, upgrades, uptime, and someone answering when login breaks.

Which Auth0 alternative supports SAML SSO? All the ones listed here. The pricing differs sharply: Auth0 charges $100/month per connection beyond included ones, Clerk charges $75/month per connection beyond the first, Supabase meters SAML at $0.015 per MAU past 50 users, Firebase prices SAML/OIDC users at $0.015 per MAU, and Blocks, Keycloak, Ory, and Zitadel include SAML in their open source versions.

How hard is it to migrate off Auth0? Most providers support importing password hashes. Ory explicitly markets bulk password hash import and webhook-based migration from Auth0. User migration is the small half; the bigger work is rewriting Actions, rules, and tenant configuration against the new provider's model.