Auth0 FGA vs. WorkOS FGA: Two Different Approaches to Fine-Grained Authorization

Static role-based access control (RBAC) breaks down quickly when permissions depend on relationships between users, resources, and organizations.

Both Auth0 and WorkOS offer fine-grained authorization (FGA) solutions to address these challenges. But they take fundamentally different approaches.

Auth0 FGA implements traditional Zanzibar-style authorization with schema languages and graph synchronization.

WorkOS FGA extends familiar RBAC patterns into a flexible, hierarchical model—delivering fine-grained power without the complexity tax.

This article explores what each platform offers, how their architectures differ, and why teams building enterprise SaaS increasingly choose WorkOS.

The Problem with Traditional FGA

Most SaaS teams begin with basic RBAC and quickly outgrow it. Users need different permissions for different resources. A user might be an Admin for one workspace, an Editor for a single project, and only a Viewer for a specific document. Flat RBAC can't express these differences without creating dozens of role variants.

Traditional FGA systems—inspired by Google's Zanzibar paper—solve this by modeling permissions as a graph of relationships. You define entities, relations, and rules in a schema language, then sync your entire resource graph to an external authorization system. Every permission check traverses this graph.

This approach is powerful. It's also complex. Teams must learn domain-specific languages, maintain schemas that evolve with their product, keep millions of resources synced with an external system, and manage the operational overhead of graph-based authorization at scale.

The deeper issue: traditional FGA assumes you can anticipate your long-term authorization model. But in real SaaS products, new resource types, collaboration patterns, enterprise requirements, and AI-driven workflows appear continuously. The access model shifts with every release.

What is Auth0 FGA?

Auth0 Fine-Grained Authorization (FGA) is a traditional Zanzibar-style authorization platform. Developed by the Auth0 team (now part of Okta), it implements relationship-based access control using tuples, relations, and a graph-based evaluation engine.

The core engine is available as OpenFGA, an open-source project that reached CNCF Incubating status in October 2025. Auth0 FGA is the managed cloud service built on top of OpenFGA.

How Auth0 FGA Works

Auth0 FGA uses three core primitives:

Objects represent entities in your system: users, documents, folders, organizations. Each has a type and unique identifier.

Relations define relationships between objects: "member," "owner," "viewer," "editor." Relations can be direct or derived through rules.

Tuples store these relationships in the authorization database. A tuple like (user:alice, member, team:engineering) states that Alice is a member of the engineering team.

To use Auth0 FGA, you write an authorization model in their domain-specific language:

model
 schema 1.1

type user

type document
 relations
   define owner: [user]
   define editor: [user, team#member]
   define viewer: [user] or editor or owner

type team
 relations
   define member: [user]

Then you sync relationship tuples to Auth0 FGA as your application creates, updates, and deletes resources. Authorization checks query the graph to determine if a valid relationship path exists.

Auth0 FGA Strengths

Auth0 FGA delivers genuine Zanzibar capabilities. The graph-based architecture handles complex transitive relationships. The authorization modeling language is expressive. Performance is optimized for millisecond-level checks. And the OpenFGA open-source foundation provides transparency and self-hosting options.

For teams that need the full power of Zanzibar-style authorization and are willing to invest in the operational complexity, Auth0 FGA is a capable solution.

Auth0 FGA Challenges

The traditional Zanzibar approach introduces real friction:

Schema complexity: Teams must learn a domain-specific language to define authorization models. Changes to the model require careful analysis of how new relationships affect existing access.

Sync overhead: Every resource in your application must be synced to Auth0 FGA as relationship tuples. For high-cardinality resources—millions of documents, records, or objects—this creates operational fragility. Drift, failed updates, and out-of-sync edges become real risks.

Migration burden: Moving from RBAC to Auth0 FGA isn't incremental. You're adopting a new mental model, new languages, and new infrastructure.

Enterprise-only pricing: Auth0 FGA requires an enterprise contract for production use. There's a free trial for evaluation, but it has no SLA and community-only support. You can't gradually adopt the platform—you commit to an enterprise contract or you don't use it in production.

What is WorkOS FGA?

WorkOS FGA takes a different approach. Rather than implementing traditional Zanzibar with schemas and graph sync, WorkOS extends familiar RBAC patterns into a flexible, hierarchical model that grows naturally with your application.

The insight: most SaaS products don't need to model arbitrary graph relationships. They need resource-scoped permissions that follow their natural product hierarchy—organizations, workspaces, projects, applications. WorkOS FGA brings these structures directly into the authorization model without requiring a DSL, schema language, or external graph layer.

How WorkOS FGA Works

WorkOS FGA extends RBAC across your product's resource hierarchy. You define resource types that mirror your application's structure, and roles can be assigned at any layer:

• A Workspace Admin inherits access to all projects in that workspace
• A Project Editor can modify only the project to which they're assigned
• An App Auditor can view only a specific application inside a project

Inheritance, scoping, and permission propagation happen automatically. There's no schema language to learn—developers work with the same RBAC patterns they know, applied at more granular levels.

Key architectural differences from traditional FGA:

No DSL required: Define resource types and roles through APIs and SDKs, not schema languages. The model is code, not configuration.

Smart high-cardinality handling: Instead of syncing every resource instance to an external system, applications store high-cardinality resources locally and register only stable parent resources with WorkOS. Authorization stays fast and consistent without forcing high-traffic resources to depend on remote calls.

Incremental adoption: No migration required from existing RBAC. Your current model continues to work. You can adopt FGA capabilities incrementally—adding resource hierarchies, inheritance rules, and fine-grained scoping as your product matures.

Up to 5 layers of hierarchy: Model real product structures with multiple resource types per layer, automatic parent-to-child permission flow, and guardrails that prevent orphaned assignments.

WorkOS FGA for AI Agents

As applications move toward agent-driven actions and AI-powered features, authorization requirements shift. Agents must not inherit a user's full permissions. They must operate with scoped, time-limited access. Access checks must be deterministic inside probabilistic systems. Document retrieval for RAG must be filtered by authorization before being passed to an LLM.

WorkOS FGA provides the building blocks for safe AI-powered systems. Applications can check fine-grained access for every document, scope permissions for task-oriented bots, and enforce policy boundaries cleanly. Authorization becomes a guardrail system that protects the enterprise while enabling AI-driven automation.

Auth0 FGA vs. WorkOS FGA: Key Differences

The Complexity Question

Auth0 FGA gives you the full power of Zanzibar. You can model arbitrary relationships, complex transitive rules, and sophisticated permission graphs. That power comes with operational cost: schemas to maintain, resources to sync, languages to learn, and infrastructure to manage.

WorkOS FGA gives you fine-grained authorization without the complexity tax. The tradeoff is intentional—by focusing on hierarchical resource patterns (which cover the vast majority of SaaS authorization needs), WorkOS delivers comparable power with dramatically simpler operations.

For most B2B SaaS applications, the hierarchical model is the right abstraction. Organizations contain workspaces contain projects contain resources. Permissions flow down the hierarchy with predictable inheritance. This is what WorkOS FGA is optimized for.

The Integration Question

Auth0 FGA is a standalone authorization service. It works with any identity provider, including Auth0's own identity platform. But that integration isn't automatic—you're connecting separate systems.

WorkOS FGA integrates natively with the complete WorkOS identity platform:

SSO and Directory Sync: Enterprise customers can map IdP groups directly to application roles. An Okta group representing the Finance team can be mapped to a workspace-level role, ensuring users arrive with correct access from day one.

Automated provisioning: IdP attributes like department, cost center, or job function can automatically assign roles at any level of your resource hierarchy. Access stays in sync with the enterprise directory without manual permission management.

Unified audit logs: Authorization events flow into the same audit log as authentication events, giving you complete visibility into who accessed what and how they got that access.

This integration matters for enterprise sales. When your authorization system knows about your directory sync, user provisioning events automatically update permissions. When an employee is deprovisioned via SCIM, their access is revoked across the entire hierarchy without manual intervention.

The Pricing Question

Auth0 FGA requires an enterprise contract for production use. The free trial is for evaluation only—no SLA, community-only support, and explicit limitations. You can't gradually scale into production.

WorkOS FGA is designed to be adopted incrementally and to grow with your application's needs. This removes adoption friction and lets teams validate their authorization model before committing to a vendor relationship.

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When to Choose WorkOS FGA

WorkOS FGA is the right choice if:

• Your authorization model follows natural product hierarchies (organizations, workspaces, projects, resources)
• You want fine-grained permissions without learning a new language or maintaining schemas
• You need to integrate authorization with SSO, SCIM, and enterprise identity workflows
• You're migrating from RBAC and want an incremental path rather than a full rewrite
• You're building AI-powered features that need scoped, deterministic authorization
• You want transparent pricing with a generous free tier

For the majority of B2B SaaS applications, WorkOS FGA delivers the authorization capabilities enterprises require—without the operational complexity of traditional Zanzibar implementations.

The Bottom Line

Fine-grained authorization has become essential for modern applications. Both Auth0 FGA and WorkOS FGA can handle complex permission models. But they represent different philosophies.

Auth0 FGA says: "Here's the full power of Zanzibar. Learn the language, sync your graph, manage the complexity."

WorkOS FGA says: "Here's fine-grained authorization that extends what you already know. No new languages, no graph sync, no migration—just RBAC that grows with your product."

For teams building B2B SaaS, the choice often comes down to whether you need arbitrary graph relationships (Auth0 FGA) or hierarchical resource permissions (WorkOS FGA). Most applications need the latter.

WorkOS FGA delivers that capability as part of a complete enterprise identity platform—with SSO, Directory Sync, and Admin Portal included. No enterprise contracts required to get started. No complexity tax to pay as you scale.

Ready to add fine-grained authorization without the fine-grained complexity? Get started with WorkOS FGA.

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