CASL vs Keycloak

Side-by-side — pricing, strengths, tradeoffs, and fit.

CASL

Isomorphic authorization for UI and API.

Keycloak

Open source identity and access management

At a glance

Open SourceFree Tier
● Established·From $0
Open SourceFree Tier
● Established·From Free / Open Source

Overview

One-liner

Isomorphic authorization for UI and API.

One-liner

Open source identity and access management

Maturity

Established

Maturity

Established

Open source

✓ Yes

Open source

✓ Yes

Pricing

Free tier

✓ Available

Open source — free to use

Free tier

✓ Available

Starts at

$0

Starts at

Free / Open Source

Model

Flat rate

Model

Flat rate

Enterprise

✕ None

Enterprise

✕ None

Best for

✓ Best for

Teams building full-stack JavaScript/TypeScript applications requiring consistent authorization rules across UI and API layers.
Projects needing a flexible, type-safe approach to defining access control policies.

✓ Best for

Teams requiring fully self-hosted auth with SAML, OIDC, and user federation — especially in regulated industries

Not ideal for

✕ Not for

Applications that require real-time updates of authorization rules without reloading the application
Scenarios where extremely low latency is critical for rule evaluation

✕ Not for

Teams wanting managed auth with zero infrastructure overhead

Strengths

↑ Strengths

Isomorphic authorization for both frontend and backend
Supports TypeScript with type-safe rules
Flexible rule definitions using predicates and actions
Extensive documentation and community support

↑ Strengths

SSO
SAML 2.0
OpenID Connect
User federation

Weaknesses

↓ Weaknesses

Steep learning curve for non-JavaScript developers
Limited community support and small user base
Performance overhead in complex rule evaluations

↓ Weaknesses

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Full CASL profile →Full Keycloak profile →