Keycloak
Open source IAM solution - European alternative based in United Kingdom
Quick Overview
| Company | Keycloak |
|---|---|
| Category | Identity Management |
| Headquarters | London, United Kingdom |
| EU/European | Yes - United Kingdom |
| Open Source | Yes |
| GDPR Compliant | Yes |
| Main Features | SSO, Identity brokering, User federation, OAuth2/OIDC, LDAP support |
| Pricing | Free (open source) |
| Best For | Enterprises needing self-hosted IAM |
| Replaces | Auth0, Okta |
Detailed Review
Keycloak has established itself as the leading open-source identity and access management (IAM) solution since its initial release by Red Hat in 2014. Now a Cloud Native Computing Foundation (CNCF) incubating project and stewarded under the Red Hat / IBM umbrella, Keycloak provides enterprise-grade single sign-on (SSO), identity brokering, user federation, and fine-grained authorization capabilities -- all without vendor lock-in or recurring license fees. For organizations seeking an alternative to Auth0, Okta, OneLogin, or Azure AD, Keycloak delivers comparable functionality with the transparency and flexibility that only open-source software can offer.
What makes Keycloak particularly compelling in 2026 is its maturity. With over a decade of active development, thousands of production deployments worldwide, and a vibrant community of contributors, Keycloak is far from experimental. Major enterprises, government agencies, and universities rely on it to secure access for millions of users. The project's move to the CNCF in 2023 further cemented its position as a vendor-neutral, community-driven standard for identity management.
Core Architecture and Quarkus Foundation
Keycloak underwent a major architectural overhaul in recent years, migrating from the WildFly application server to Quarkus -- a Kubernetes-native Java framework designed for fast startup times and low memory consumption. The Quarkus-based distribution, now the default, starts in seconds rather than minutes and uses significantly less RAM, making Keycloak far more practical for containerized and cloud-native deployments. This migration also simplified configuration, replacing complex XML files with a streamlined command-line interface and environment-variable-driven setup.
Under the hood, Keycloak stores its data in a relational database (PostgreSQL, MySQL, MariaDB, or Microsoft SQL Server) and uses Infinispan for distributed caching across clustered deployments. The architecture supports horizontal scaling, meaning you can run multiple Keycloak instances behind a load balancer for high availability. For organizations handling millions of authentications per day, this clustering capability is essential.
Single Sign-On and Protocol Support
Keycloak supports the full spectrum of modern authentication protocols: OpenID Connect (OIDC), OAuth 2.0, and SAML 2.0. This means it can integrate with virtually any application -- whether a modern single-page web app using OIDC, a legacy enterprise system requiring SAML, or a mobile application using OAuth 2.0 authorization flows. The Admin Console provides a centralized interface for managing all protocol configurations, client applications, and authentication flows.
SSO works seamlessly across applications registered with the same Keycloak realm. Once a user authenticates through Keycloak, they can access any connected application without re-entering credentials. Session management is granular: administrators can view active sessions, force logouts, set idle and maximum session timeouts, and configure remember-me functionality. Keycloak also supports single logout, ensuring that signing out of one application terminates sessions across all connected services.
Identity Brokering and Social Login
Keycloak excels as an identity broker, meaning it can authenticate users against external identity providers and map those identities into its own system. Out of the box, it supports identity brokering with any OIDC or SAML provider, plus pre-configured connectors for Google, Facebook, GitHub, Twitter, LinkedIn, Microsoft, and many others. This is particularly useful for organizations that need to accept logins from partners, customers, or social accounts while maintaining a unified user directory.
First-login flows are fully configurable: when a user authenticates via an external provider for the first time, Keycloak can automatically create a local account, prompt the user to link to an existing account, or require email verification. Attribute mapping allows organizations to pull user profile data from external providers and normalize it into a consistent schema within Keycloak.
User Federation with LDAP and Active Directory
For enterprises with existing directory services, Keycloak provides robust LDAP and Active Directory federation. Rather than migrating all users into Keycloak's internal database, user federation allows Keycloak to authenticate against the external directory in real time. This means existing password policies, group memberships, and user attributes remain authoritative in LDAP or AD, while Keycloak handles the modern protocol translation (exposing LDAP users via OIDC or SAML).
Keycloak supports multiple federated directories simultaneously, full and changed-only synchronization, attribute mapping between LDAP schemas and Keycloak user models, and group-to-role mapping. For organizations undergoing gradual migrations from legacy infrastructure, Keycloak's federation capabilities allow a phased transition without forcing a big-bang directory migration.
Multi-Factor Authentication and Adaptive Security
Keycloak includes built-in support for multi-factor authentication (MFA) including time-based one-time passwords (TOTP) compatible with Google Authenticator and similar apps, WebAuthn/FIDO2 hardware security keys, and email-based OTP verification. Authentication flows are modular and configurable through the Admin Console: organizations can require MFA for all users, enforce it conditionally based on risk signals, or offer it as an optional step that users can enable for their own accounts.
WebAuthn support is particularly noteworthy. As passwordless authentication gains traction, Keycloak's FIDO2 support allows users to authenticate using biometric sensors, hardware keys like YubiKeys, or platform authenticators built into modern laptops and smartphones. The implementation supports both user verification (passwordless) and second-factor (MFA with WebAuthn as the second step) scenarios.
Fine-Grained Authorization Services
Beyond authentication, Keycloak provides an authorization server compliant with the User-Managed Access (UMA) 2.0 specification. This enables fine-grained, policy-based access control where permissions are evaluated centrally rather than being hardcoded into each application. Policies can be based on roles, user attributes, time, JavaScript rules, or combinations of these factors. For organizations building complex multi-tenant applications or APIs with granular permission models, this centralized authorization engine reduces duplication and security inconsistencies across services.
Customization and Extensibility
One of Keycloak's greatest strengths is its extensibility through the Service Provider Interface (SPI). Nearly every aspect of Keycloak's behavior can be customized by implementing Java interfaces: custom authentication steps, user storage providers, event listeners, token mappers, protocol mappers, and theme providers. This means organizations are never locked into Keycloak's default behavior -- if a specific business requirement demands a unique authentication flow or integration, it can be built as an SPI extension without forking the core project.
Theming is comprehensive as well. The login pages, account management console, and admin console can all be fully restyled using FreeMarker templates and CSS. Organizations can present a fully branded login experience to their users while leveraging Keycloak's underlying security infrastructure. The recent introduction of the Account Console v3 (built with React/PatternFly) provides a more modern user self-service experience.
Deployment Options and Kubernetes Integration
Keycloak runs wherever Java runs, but its primary deployment target in 2026 is Kubernetes. The official Keycloak Operator for Kubernetes simplifies deployment, upgrades, and configuration management in containerized environments. Combined with the Quarkus runtime, Keycloak fits naturally into GitOps workflows: infrastructure-as-code tools like Helm charts and Kustomize overlays can fully automate Keycloak deployment and realm configuration.
For organizations not using Kubernetes, Keycloak ships as a standalone distribution that runs on any server with a JVM, as well as official Docker images. Cloud-specific deployment guides exist for AWS, Azure, and Google Cloud, and the Quarkus runtime's fast startup makes it suitable for environments where auto-scaling and rapid provisioning are important.
Red Hat Build of Keycloak (Commercial Support)
Organizations that require commercial support, certified binaries, and long-term maintenance can opt for the Red Hat build of Keycloak (formerly Red Hat Single Sign-On). This provides the same core software with Red Hat's enterprise support SLAs, security patching commitments, and certified container images. The commercial offering is particularly important for regulated industries -- financial services, healthcare, and government organizations often require vendor-backed support as a compliance requirement.
Data Sovereignty and GDPR Considerations
Because Keycloak is self-hosted, organizations have complete control over where their identity data resides. There is no data leaving your infrastructure to a third-party cloud service -- unlike Auth0 (US-based, Okta subsidiary), Okta (US-based), or Azure AD (Microsoft, US-based). For European organizations subject to GDPR, Schrems II considerations, or sector-specific data residency requirements, this self-hosted model eliminates the legal complexity of transatlantic data transfers entirely.
Keycloak also supports data retention policies, user consent management, and the right to erasure (user account deletion) required by GDPR. The admin API enables automation of data subject access requests, and audit logging provides the traceability that compliance officers require.
Community and Ecosystem
Keycloak benefits from one of the largest open-source IAM communities. The project has over 20,000 GitHub stars, hundreds of contributors, and an active discussion forum. The ecosystem includes community-maintained extensions for SMS-based OTP, Kerberos, Apple Sign-In, and many other authentication methods. Comprehensive documentation, a developer mailing list, and regular community meetings ensure that organizations adopting Keycloak have abundant resources for implementation support.
Who Should Choose Keycloak
Keycloak is best suited for organizations that need enterprise-grade identity management with full control over their infrastructure and data. It is the strongest choice for European companies seeking GDPR-compliant IAM without reliance on US cloud services, for enterprises requiring LDAP/AD federation alongside modern OIDC/SAML protocols, and for technical teams comfortable with self-hosted Java applications. Startups or small teams without dedicated DevOps resources may find managed alternatives like Auth0 easier to start with, but for any organization prioritizing sovereignty, transparency, and long-term flexibility, Keycloak is the standard-bearer in open-source identity management.
Alternatives to Keycloak
Looking for other European identity management solutions? Here are some alternatives worth considering:
Frequently Asked Questions
Yes. Because Keycloak is self-hosted, your identity data never leaves your own infrastructure. This means you have complete control over data residency and can ensure all personal data is processed and stored within the EU. Unlike cloud-based IAM services like Auth0 or Okta, there are no transatlantic data transfers to worry about. Keycloak also supports GDPR requirements such as user consent management, right to erasure (account deletion), and comprehensive audit logging for data subject access requests.
Keycloak provides most of the same core features as Auth0 and Okta -- SSO, social login, MFA, OIDC/SAML support, and user management -- but as a self-hosted, open-source solution rather than a proprietary SaaS. The key advantages of Keycloak are zero licensing costs, complete data sovereignty, full customizability through its SPI architecture, and no vendor lock-in. The trade-off is that you manage your own infrastructure and upgrades. Auth0 and Okta offer a more polished out-of-the-box experience with managed hosting, but at significant cost (Auth0 Enterprise plans can exceed $20,000/year) and with your data stored in US-controlled cloud infrastructure.
Keycloak itself is completely free and open source under the Apache 2.0 license. There are no per-user fees, no feature gates, and no usage limits in the software. Your only costs are infrastructure (server hosting, database) and the engineering time to deploy and maintain it. For organizations that need commercial support, Red Hat offers the Red Hat build of Keycloak with enterprise SLAs and certified binaries as part of their middleware subscription.
Yes. Keycloak supports horizontal scaling through clustering, where multiple Keycloak instances share session data via Infinispan distributed caching. Large-scale deployments with millions of users are well documented in the community. The Quarkus-based runtime significantly reduces per-instance memory consumption and startup time, making auto-scaling practical. The key to scaling Keycloak is database performance -- PostgreSQL with proper indexing and connection pooling handles high-throughput authentication workloads effectively.
Yes. Keycloak supports WebAuthn/FIDO2, which enables passwordless authentication using biometric sensors (fingerprint, face recognition), hardware security keys like YubiKeys, and platform authenticators built into modern devices. You can configure authentication flows to offer passwordless as the primary method or as a second factor alongside traditional passwords. This is configured through Keycloak's flexible authentication flow editor in the Admin Console.
Keycloak provides an official Kubernetes Operator that manages the full lifecycle of Keycloak deployments including provisioning, upgrades, and configuration. You can also deploy using Helm charts or Kustomize manifests. The Quarkus-based runtime is optimized for containers with fast startup times (typically under 5 seconds) and reduced memory footprint. Official Docker images are published for each release, and the deployment can be fully automated through GitOps workflows.
Yes. Keycloak provides built-in LDAP and Active Directory federation, allowing it to authenticate users against existing directory services without migrating them into Keycloak's internal database. It supports multiple directories simultaneously, full and incremental synchronization, attribute mapping, and group-to-role mapping. This makes Keycloak ideal for organizations that want to keep their existing AD/LDAP infrastructure while adding modern OIDC and SAML capabilities.
Yes. Keycloak's realm concept provides natural multi-tenancy -- each realm is a completely isolated identity namespace with its own users, roles, clients, and authentication settings. A single Keycloak instance can host hundreds of realms. Additionally, Keycloak Organizations (introduced in recent versions) provide organizational grouping within a realm for finer-grained multi-tenancy. For SaaS platforms serving multiple customers, Keycloak's multi-realm architecture provides strong isolation without requiring separate deployments per tenant.
Keycloak itself is written in Java, but it integrates with applications in any language through standard protocols (OIDC, OAuth 2.0, SAML). Official and community-maintained client adapters and SDKs are available for Java, JavaScript/Node.js, Python, Go, .NET, PHP, Ruby, and more. The Admin REST API enables programmatic management from any language, and Keycloak's JavaScript adapter makes frontend integration straightforward for React, Angular, and Vue applications.
Keycloak has one of the most active open-source IAM communities. The project has over 20,000 stars on GitHub with hundreds of contributors. As a CNCF incubating project, it benefits from vendor-neutral governance and broad industry support. The community maintains an active discussion forum, regular release cadence (new versions every few months), and extensive documentation. Major organizations including Red Hat, Bosch, and various government agencies contribute to the project.