Oso

Oso is a platform and framework for building authorization into applications — the logic that determines who can do what, and what data they can access. Authorization is a critical, surprisingly hard part of nearly every application: as products grow, permissions become complex (roles, hierarchies, sharing, multi-tenancy), and getting them right is essential for security but tedious and error-prone to build and maintain. Oso provides tools and infrastructure to model, build and enforce authorization cleanly, so developers don't have to reinvent this complex logic from scratch.

Oso lets developers define their authorization rules in a clear, declarative way and enforce them consistently throughout their application, handling common patterns like role-based access control, relationship-based permissions, and multi-tenancy. By centralizing and structuring authorization logic — rather than scattering ad-hoc permission checks throughout the codebase — Oso makes permissions easier to reason about, maintain and get right, reducing both security risk and developer pain. It offers libraries and a cloud service to fit different needs, helping teams build sophisticated authorization without building all the underlying machinery themselves.

Oso is used by development teams that need robust, maintainable authorization in their applications and want to avoid the pitfalls of building it ad hoc. By providing a principled way to model and enforce who can access what, it helps teams ship secure features faster and keep their permissions correct as their product and requirements evolve — which is increasingly important as applications grow more complex and security expectations rise. Its developer-focused approach makes a traditionally thorny problem more tractable. As authorization remains a universal and challenging need in software, dedicated tools and frameworks for it are genuinely valuable. For development teams that want to build and enforce application authorization cleanly and reliably — modeling who can do what without reinventing the wheel — Oso offers a capable, well-designed and developer-friendly solution.