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Developer Tools · head to head

Keycloak vs Preact

Keycloak logo

Keycloak

Developer Tools

Open-source identity and access management server.

From
Free
Free plan
Yes
Full reviewWebsite
Preact logo

Preact

Web Development

3kB alternative to React with the same modern API

From
Free
Free plan
Yes
Full reviewWebsite

The short version

  • Each has a real cost: Keycloak requires self-hosted deployment and operational expertise to install, configure and maintain; Preact compatibility through preact/compat is good but not total, and some React libraries break in ways that are hard to diagnose
  • Prices and features above were last checked on 29 August 2026.

Where they differ

Only the attributes on which Keycloak and Preact actually diverge.

Attributes where Keycloak and Preact differ
AttributeKeycloakPreact
Pricing modelopen-sourceOpen source, no licence fee
PlatformsSelf-hosted, Docker, Kubernetes, Linux, Windows, APIWeb
CategoryDeveloper ToolsWeb Development

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Keycloak

Nothing recorded that Preact does not also cover.

Only in Preact

  • 3kB runtime
  • preact/compat
  • Same modern API
  • Fast rendering

What people use each for

The jobs each tool is most often brought in to do.

Keycloak

  • Organisations requiring self-hosted identity infrastructure for compliance or data residencynot Preact
  • Companies with existing LDAP/Active Directory systems needing federated authenticationnot Preact
  • Open-source projects and communities requiring free IAM without licensing costsnot Preact
  • Enterprises building custom identity workflows requiring fine-grained authorisationnot Preact
  • Teams with sufficient operational expertise to manage infrastructurenot Preact

Preact

  • Embedded widgets that load inside someone else’s page and must stay smallnot Keycloak
  • Marketing and content sites where JavaScript payload affects Core Web Vitalsnot Keycloak
  • Applications targeting low-bandwidth or low-powered devicesnot Keycloak

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Keycloak

  • Requires self-hosted deployment and operational expertise to install, configure and maintain
  • No managed cloud option provided by Red Hat; organisations must operate infrastructure themselves or use third-party distributions
  • Clustering and high-availability configurations require additional operational knowledge
  • Community support only; commercial support requires third-party vendors or distributions

Preact

  • Compatibility through preact/compat is good but not total, and some React libraries break in ways that are hard to diagnose
  • Behavioural differences from React exist in edge cases, particularly around event handling
  • A much smaller community, so unusual problems have fewer existing answers than React

Pricing, plan by plan

Keycloak

Free
  • Open-sourceFree
    • Full platform functionality
    • Self-hosted deployment
    • Community support

Preact

Free
  • PreactFree
    • Full library
    • Commercial use permitted
    • No usage limits

Which should you pick?

Choose Keycloak if

  • You want to start without paying.
  • You work on Self-hosted, Docker, Kubernetes, Linux, Windows, API.
Keycloak review

Choose Preact if

  • You need 3kb runtime.
  • You want to start without paying.
  • You also want preact/compat.
Preact review

Questions people ask

Is Keycloak or Preact better?
Neither clearly leads. Keycloak starts at Free and Preact at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Keycloak or Preact?
Keycloak starts at Free and Preact at Free.
Does Keycloak or Preact run on more platforms?
Keycloak runs on Self-hosted, Docker, Kubernetes, Linux, Windows, API. Preact runs on Web.
Can I use Keycloak for free?
Both have a free tier, so you can try either at no cost before committing.
What is Keycloak best used for?
Keycloak is most often used for organisations requiring self-hosted identity infrastructure for compliance or data residency, companies with existing ldap/active directory systems needing federated authentication, open-source projects and communities requiring free iam without licensing costs, enterprises building custom identity workflows requiring fine-grained authorisation. Of those, organisations requiring self-hosted identity infrastructure for compliance or data residency and companies with existing ldap/active directory systems needing federated authentication are not what Preact is typically brought in for.
What can Keycloak do that Preact cannot?
Preact covers 3kB runtime, preact/compat, Same modern API, Fast rendering.

Answered from the vendors’ own pages

Keycloak: What protocols does Keycloak support?

Keycloak supports OpenID Connect, OAuth 2.0 and SAML 2.0 protocols for authentication and authorisation.

Source
Preact: Is Preact free?

Yes, open source under the MIT licence.

Keycloak: Can Keycloak integrate with existing user directories?

Yes. Keycloak supports user federation with LDAP and Active Directory systems, allowing organisations to leverage existing user directories.

Source
Preact: Can I use React libraries with Preact?

Most, through the preact/compat layer. Compatibility is good but not complete, so libraries relying on React internals can break.

Keycloak: Is Keycloak free?

Yes. Keycloak is fully open-source and free to deploy and use. No licensing fees are required.

Source
Preact: Why choose Preact over React?

Bundle size, almost always. If payload is not a binding constraint, React’s ecosystem is usually the better trade.

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