Keycloak: An Open-Source Auth0 & Okta Alternative (2026)

I lead ERPNext and open-source identity work at MithTech, a team of Frappe specialists in Bengaluru. Identity is often the second conversation after the first app goes live: once a team has ERPNext, a helpdesk, a BI tool and a chat app, nobody wants four logins; they want one identity and one password policy. Auth0 and Okta do that well, but they are proprietary and billed per user, so I am often asked for the open-source equivalent. What follows maps to the Keycloak documentation and Auth0's published pricing. Keycloak is not something you set up in an afternoon and forget; it is infrastructure you have to run. For a team that wants to own its identity layer and skip per-seat billing, that trade is usually worth it.

Which open-source tools replace Auth0?

Keycloak is the most established: a full identity and access management platform under Apache 2.0, self-hosted, with no licence fee or user limit. It has been around longest of the open-source options and covers the most standards.

Other open-source contenders include Authentik, Authelia, Zitadel and Ory, each with a niche: Authelia is a lightweight gate in front of a reverse proxy, Authentik has a modern admin interface, Ory offers API-first building blocks for developers. Keycloak is the closest general-purpose match for what Auth0 and Okta do: centralise login, issue tokens, federate existing directories, broker social and enterprise logins, and enforce access policy across many applications.

Skimmable summary: Keycloak is the longest-established, most standards-complete open-source alternative to Auth0 and Okta, with no licence fee to self-host.

What is Keycloak, and how does it work?

Keycloak is an identity and access management server that sits between your users and your applications. Applications hand login to Keycloak; Keycloak checks the user (against its own database, an LDAP directory or an external identity provider) and returns a signed token the application trusts. One login then opens every connected app: single sign-on.

The core building block is the realm, an isolated space with its own users, roles, clients and login policies. Inside a realm you register each application as a client using OpenID Connect or SAML 2.0, and Keycloak handles the rest: login screens, tokens, refresh and logout. Because it speaks the open standards, most modern apps and frameworks connect without custom glue. It also brokers identity, handing off to Google, Microsoft, GitHub or any SAML or OIDC provider and turning the result into one session.

Keycloak runs on your own Linux server, Docker or Kubernetes, backed by a database such as PostgreSQL. It ships often; the current line is 26.x (26.8.0 was released on 1 October 2026). Because you host it, your user directory, password hashes and tokens stay on infrastructure you control.

Skimmable summary: Keycloak checks users and issues standard OIDC or SAML tokens your apps trust, brokering external providers, on infrastructure you own.

What can Keycloak do?

More than basic login. Single sign-on across every connected app is the headline, but it also handles multi-factor and passwordless login, directory federation and fine-grained authorization, with none of the essentials behind a paid tier.

The capabilities I use most:

• Single sign-on and single logout. One login unlocks every connected application; one logout ends the session everywhere.
• Standard protocols. OpenID Connect, OAuth 2.0 and SAML 2.0 are all first-class, so both modern apps and legacy enterprise software integrate.
• User federation. Built-in connectors to LDAP and Active Directory mean existing corporate accounts work without migrating users.
• Identity brokering and social login. Delegate to Google, Microsoft, GitHub or any external SAML/OIDC provider for staff or customer sign-in.
• Multi-factor and passwordless. One-time passwords plus FIDO2/WebAuthn passkeys.
• Fine-grained authorization. Policy-based access control that goes beyond simple roles when you need it.
• Organizations. Multi-tenant-style grouping, so customer groups or business units can manage their own users.

Skimmable summary: Keycloak ships SSO, OIDC/OAuth2/SAML, LDAP/AD federation, social login, MFA, passkeys and fine-grained authorization in the free, open-source core.

Keycloak vs Auth0 vs Okta: how do they compare?

They solve the same problem in opposite ways. Auth0 (owned by Okta) and Okta are proprietary, fully managed SaaS platforms with polished tooling and many official SDKs. Keycloak is open source and self-hosted, trading managed convenience for ownership and no per-user billing. All three deliver SSO, OIDC and SAML.

Auth0 and Okta suit you if you want no operations work, the widest set of drop-in SDKs and a polished dashboard, and per-user cost is not a concern. Keycloak suits you if you want to own the identity layer, keep user data on your terms, avoid per-seat billing, and can run the infrastructure. Auth0 and Okta pricing varies by plan and user count; check each vendor's page.

Skimmable summary: Auth0 and Okta are ahead on managed convenience and SDKs; Keycloak on ownership, data control and no per-user billing.

Where does Keycloak fall short?

Its gaps are mostly operational, not functional. Auth0 and Okta run the servers, patch the software, scale for you and give you a support line. With Keycloak, the uptime, upgrades and incident response are yours.

The gaps I flag for teams weighing the switch:

• You run the infrastructure. A production Keycloak needs a database, TLS certificates, high availability, backups and monitoring: a real DevOps project, not a signup form.
• Upgrades are on you. Keycloak releases frequently. Staying current — and reading release notes for breaking changes — is ongoing work rather than something a vendor absorbs.
• Developer experience is standards-first. The adapters are solid and the protocols open, but Auth0 invests heavily in polished quickstarts for many languages. Expect to rely on standards knowledge rather than a guided path.
• Support is community-based by default. For a vendor SLA, teams use the Red Hat build of Keycloak (the supported downstream) or a managed hosting provider.

None of these rules Keycloak out for most businesses, but they are why a team that wants no operations responsibility may still pick a managed platform.

Skimmable summary: you own hosting, upgrades and support, and the developer experience is more standards-first than Auth0's.

Who should choose Keycloak?

Teams that value ownership and want to avoid per-user billing: organisations already running open-source infrastructure, businesses with data-residency or on-premise requirements, and teams putting many applications behind one identity, where a per-seat subscription grows painfully.

Keycloak fits when you need to federate an existing Active Directory, want SSO across a growing set of internal and customer-facing apps, or need user data to stay on infrastructure you control. It fits less well if you have no appetite for running infrastructure, want the widest SDK coverage with guided quickstarts, and would rather pay for a managed service. For Indian businesses that care about cost and about where personal data sits under the DPDP Act, the self-hosted model is often a good fit.

Skimmable summary: Keycloak suits ownership-minded teams unifying SSO across many apps; it is a weaker fit for those who want a fully managed, zero-ops identity service.

How does Keycloak fit alongside ERPNext and your other apps?

Keycloak becomes the one identity layer in front of the stack. Frappe's Social Login Key has a Keycloak provider that signs users in over OpenID Connect, so Keycloak can be the login for Frappe Desk, ERPNext, Frappe CRM and other Frappe apps. Frappe has no built-in SAML; for SAML you need a community app, or you use OIDC. The same pattern extends to Grafana, Metabase, Mattermost, Nextcloud and custom apps.

We treat this as one stack, not a series of separate login decisions. ERPNext is open source under GPL-3.0 and Keycloak under Apache 2.0; both self-host and neither bills per seat. A user signs in to Keycloak once and moves between the ERP, the helpdesk, the BI dashboard and the chat tool without signing in again, while you enforce one password policy, one MFA rule and one offboarding step across all of them. Our guide to open-source SaaS alternatives maps the wider landscape, managed hosting covers how we run Keycloak, and the ERPNext platform page covers the system it most often sits in front of.

Skimmable summary: Keycloak becomes the login for ERPNext (over OIDC), Frappe apps and the rest of the stack: one sign-in, one policy, one offboarding step.

How do you migrate from Auth0 to Keycloak?

Run the move in order, and keep the old provider live until the last step:

1. Inventory what Auth0 is actually doing for you — every application, connection, social provider, rule, action, and custom claim. The list is almost always longer than the team remembers.
2. Stand up Keycloak and model one realm per tenant boundary, then recreate clients and roles. Do this on a staging host, not the box you intend to keep.
3. Migrate users in bulk with the Admin REST API. Password hashes can be imported only if Keycloak can read the algorithm: Auth0 exports bcrypt hashes through a support request, and Keycloak needs a bcrypt hash-provider extension for those. Otherwise plan a forced reset rather than a silent lockout.
4. Re-point one low-risk application first and run both providers in parallel for a week. Watch token refresh and logout, which is where mismatched session settings surface.
5. Move the remaining apps, then cut off the Auth0 tenant only after a full billing cycle with no fallback traffic.

The step teams skip is the parallel run. Identity failures are all-or-nothing for the user, so test the rollback path before you need it.

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