Quick Verdict
Authelia and Keycloak solve different problems. Authelia is a lightweight authentication gateway that adds SSO and 2FA to services behind a reverse proxy — it takes 50 MB of RAM and a YAML file. Keycloak is a full identity provider with OIDC, SAML, LDAP federation, and user management — it takes 1-2 GB of RAM and significant configuration. Most homelabs need Authelia. Enterprise-scale setups need Keycloak.
Overview
Authelia is a forward-auth server. It integrates with your reverse proxy (Nginx Proxy Manager, Traefik, Caddy) to add authentication and 2FA to any web service, even those without built-in auth. Configuration is via YAML files. It supports OIDC (as a provider), TOTP, WebAuthn, push notifications, and file-based or LDAP user backends.
Keycloak is Red Hat's open-source identity and access management platform. It's a full identity provider (IdP) supporting OIDC, SAML 2.0, LDAP/AD federation, social login, fine-grained authorization, custom themes, and user self-service. Applications integrate with Keycloak via standard protocols — they redirect to Keycloak for login and receive tokens back.
Feature Comparison
| Feature | Authelia | Keycloak |
|---|---|---|
| Primary model | Forward-auth (reverse proxy integration) | Identity provider (protocol-based) |
| OIDC provider | Yes (added in recent versions) | Yes (mature) |
| SAML | No | Yes |
| LDAP provider | No | Yes (federation) |
| LDAP consumer | Yes (as user backend) | Yes (federation, sync) |
| Active Directory | Read-only (user backend) | Full federation + sync |
| Social login | No | Yes (Google, GitHub, etc.) |
| 2FA methods | TOTP, WebAuthn, Duo Push | TOTP, WebAuthn, SMS |
| User management UI | No (file or LDAP) | Yes (full admin console) |
| User self-service | No (password reset via email) | Yes (profile, password, 2FA) |
| Flow customization | YAML rules (simple) | Visual flow editor (no), XML/JSON flows |
| Per-app policies | Yes (one_factor, two_factor, deny) | Yes (client-level, role-based) |
| Forward-auth support | Native (its entire purpose) | No (apps must integrate via OIDC/SAML) |
| Configuration | YAML files | Environment vars + web UI |
| Runtime | Go | Java (Quarkus) |
| Docker RAM | ~50 MB | ~1-2 GB |
| Docker containers | 1 (+ optional Redis, DB) | 2 (app + PostgreSQL) |
| License | Apache-2.0 | Apache-2.0 |
| GitHub stars | ~23,000 | ~26,000 |
Installation Complexity
Authelia can run as a single container with a SQLite database and file-based user store. For production, add Redis (session storage) and PostgreSQL. The main complexity is writing the configuration YAML and integrating with your reverse proxy (Traefik, Caddy, or nginx snippets). Total setup: 15-30 minutes.
Keycloak requires PostgreSQL, domain-specific settings, and understanding of realms, clients, and flows. The admin console has a learning curve. Each application needs to be registered as a client. Setup time: 1-2 hours for a working SSO setup with a few apps.
Performance and Resource Usage
| Metric | Authelia | Keycloak |
|---|---|---|
| RAM (idle) | ~50 MB | ~1 GB |
| RAM (active) | ~80 MB | ~1.5-2 GB |
| CPU | Very low (Go) | Medium (Java) |
| Disk | ~20 MB | ~400 MB |
| Startup time | <3 seconds | 30-60 seconds |
Authelia uses 20x less RAM than Keycloak. On a Raspberry Pi or small VPS, this difference is decisive.
Community and Support
Authelia has 23,000+ GitHub stars and a highly active community focused on self-hosting and homelabs. Documentation is excellent, with specific guides for every major reverse proxy. Development is steady with regular releases.
Keycloak has 26,000+ GitHub stars and Red Hat's backing. The community skews enterprise. Documentation is comprehensive but enterprise-oriented — finding homelab-specific guidance requires more searching. The ecosystem of extensions, adapters, and integrations is massive.
Use Cases
Choose Authelia If...
- You want to add auth/2FA to services that have no built-in authentication
- You're running everything behind a reverse proxy (Traefik, Caddy, Nginx Proxy Manager)
- You have <20 services and <10 users
- You want minimal resource usage (Raspberry Pi friendly)
- You don't need SAML, social login, or user self-service portals
- You want YAML-based configuration (infrastructure as code)
- Forward-auth is your primary authentication model
Choose Keycloak If...
- Your apps support OIDC/SAML natively and you want true SSO tokens
- You need SAML 2.0 support
- You need to federate users from Active Directory
- You need user self-service (profile management, password changes)
- You manage 20+ services with role-based access
- Social login (Google, GitHub) is required
- You have 1-2 GB of RAM to spare
Use Both Together
This is actually a valid pattern. Use Keycloak as your identity provider for apps that support OIDC natively (Nextcloud, Grafana, Portainer), and Authelia as a forward-auth layer for apps that don't support any auth protocol. Configure Authelia to use Keycloak as its OIDC backend for a unified login experience.
Final Verdict
Start with Authelia. It covers the most common homelab need — "put a login page in front of my services" — with minimal resources and complexity. Graduate to Keycloak when you outgrow Authelia: when you need SAML, Active Directory federation, or a proper user management portal. If you're between these two, Authentik offers a middle ground with a modern UI. See Authelia vs Authentik and Authentik vs Keycloak.
FAQ
Can Authelia do everything Keycloak does?
No. Authelia is a focused tool — forward-auth with OIDC provider capabilities. It doesn't do SAML, LDAP federation, user management UI, social login, or fine-grained authorization. These aren't missing features — they're outside Authelia's scope.
Can Keycloak replace Authelia?
For apps that support OIDC/SAML, yes. For apps with no built-in auth that need a reverse-proxy login gate, no — Keycloak doesn't do forward-auth. You'd need to put an OAuth2 proxy in front of those apps, which is more complex than Authelia.
Which uses less RAM?
Authelia by a massive margin. 50 MB vs 1-2 GB. If you're on a Raspberry Pi, Keycloak isn't an option.
Can I start with Authelia and migrate to Keycloak later?
Yes. You can add Keycloak alongside Authelia and migrate apps one by one. Start with OIDC-capable apps (point them to Keycloak), then phase out Authelia once all apps are covered.
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