Policy as Code, Everywhere: How Casbin Makes Authorization Simple, Powerful, and Portable

Developers don’t wake up excited to write yet another permission system. You want to ship features, not reinvent ACLs for the hundredth time. At Casbin, we’ve spent years turning that recurring pain into a small, composable library you can drop into any stack—and scale from a weekend project to a global platform—without changing your core code.

If you’ve heard of “policy as code,” Casbin is that idea distilled: authorization that’s model-driven, language-agnostic, storage-flexible, and ready for distributed, high-throughput production. (casbin.org)

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What is Casbin?

Casbin is an open-source authorization library that enforces many access control models—ACL, RBAC, ABAC, ReBAC, and classic lattice models like Bell–LaPadula and Biba—with the same clean API. It’s available across popular languages and runtimes: Go, Java, Node.js/JavaScript, Python, PHP, .NET, Rust, C/C++, Ruby, Swift, Lua/OpenResty, Dart/Flutter, and Elixir. Learn it once; use it everywhere. (casbin.org)

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Policy as Configuration, Not as If-Statements

Under the hood, Casbin models authorization with a simple, declarative CONF file based on the PERM metamodel (Policy, Effect, Request, Matchers). To change behavior—from plain ACL to tenant-aware RBAC or attribute-rich ABAC—you modify the model file, not your application logic. You can even combine models (e.g., RBAC roles with ABAC attributes) and share one policy set. (casbin.org)

A minimal model includes five sections—request_definition, policy_definition, policy_effect, matchers, and (if you use roles) role_definition. That structure keeps policies readable, testable, and version-controllable. (casbin.org)

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Why Teams Choose Casbin

1) Rich Models for Real Apps

Beyond basic RBAC, Casbin supports resource roles, multi-tenant domains, and ABAC with ergonomic syntax (e.g., resource.Owner). That lets you express nuanced rules—“project editors can update files they own within their tenant”—without bespoke code. (casbin.org)

2) Storage That Fits Your Stack

Policies can live in memory or files during development, and move to production stores with a one-line adapter swap: MySQL, Postgres, Oracle, MongoDB, Redis, Cassandra, AWS S3, and more. No lock-in, no migration drama. (casbin.org)

3) Production-Ready Distribution

Running many instances? Watchers (e.g., via etcd or messaging systems) keep enforcers consistent across nodes, so permission changes propagate safely and quickly in distributed environments. (casbin.org)

4) Run It as a Service

Prefer a network boundary? Use Casbin Server (gRPC) for “Authorization-as-a-Service,” exposing both Management and RBAC APIs to any client. (casbin.org)

5) Works Where You Work

From web frameworks to GraphQL servers, Casbin plugs in through middleware across languages, so enforcement happens right where requests flow. (casbin.org)

6) Developer-Friendly Tooling

Try ideas in the Casbin Online Editor—with syntax highlighting, completion, and even AI-assisted authoring—to iterate on models and policies before you wire them into production. (casbin.org)

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A Five-Minute Mental Model

1. Model: describe the world—what a request looks like, what a policy looks like, and how to match them. (That’s your model.conf.)
2. Policy: list the rules—who can do what on which resource. (That’s your policy.csv or records in your adapter storage.)
3. Enforcer: load the model + policy, then call enforce(sub, obj, act) anywhere you need a decision. (casbin.org)

At runtime, Casbin evaluates your request against policies and returns true/false. If at least one policy matches, access is granted—no boilerplate conditionals leaking into every controller. (casbin.org)

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Scaling from Startup to Enterprise

• Multi-tenant SaaS: Use domain-aware RBAC so the same user can have different roles per workspace or tenant. (casbin.org)
• Data governance: Express lattice policies (BLP/Biba) where confidentiality/integrity levels matter. (casbin.org)
• APIs & GraphQL: Enforce per-field or per-resolver permissions with lightweight middlewares. (casbin.org)
• Hybrid storage: Start with files, move to Redis or Postgres when you need centralized policy management—no app rewrite. (casbin.org)
• Global traffic: Keep nodes in sync with Watchers so policy updates propagate fast and safely. (casbin.org)

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Developer Experience Highlights

• Same API across languages: shift teams or microservices without re-learning authorization. (casbin.org)
• Dynamic policy management: Add, remove, or update rules at runtime via Management APIs. (casbin.org)
• Testability: Models and policies are plain text—version them, review them, and CI them just like code. (Try changes in the Online Editor before merging.) (casbin.org)

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Casbin in the Ecosystem

Casbin integrates with community tools and gateways (e.g., via plugins or middleware), and our broader ecosystem includes companion projects like Casnode (community forum) and Casdoor (open-source identity), both maintained by our community. (casbin.org)

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Getting Started

1. Pick your SDK (Go, Java, Node.js, Python, etc.).
2. Create a model.conf (start from RBAC; evolve as needed).
3. Load policies from a file in dev, then swap to an adapter for your database.
4. Enforce decisions at the edge of your app (HTTP handlers, RPC methods, resolvers). (casbin.org)

And if you want a central service today, spin up Casbin Server and point your apps to it via gRPC. (casbin.org)

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Why This Matters Now

Modern products juggle tenants, roles, attributes, and ever-changing rules. Hard-coding those rules into controllers calcifies your codebase. With Casbin, authorization becomes a living contract: readable by humans, testable in CI, auditable for compliance, and swappable without touching your business logic. That’s less risk, less drift, and more velocity.

We built Casbin so you can stop writing authorization again and start evolving it—confidently.

Try Casbin, design your model, and ship permissions that scale. (casbin.org)

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Casbin is open source and maintained by the Casbin community and Casbin Inc. Contributions are welcome across languages, adapters, and integrations. (casbin.org)