Fine-Grained Authorization
FGA.
An authorization category that permits permissions per individual resource instance, typically implemented via Zanzibar-style ReBAC, supporting billions of objects with sub-millisecond evaluation.
FGA and ReBAC overlap heavily in practice, most modern FGA implementations are ReBAC implementations. The distinction is mostly about emphasis: ReBAC describes the data model; FGA describes the use case (per-resource permissions at scale). When a CIAM advertises "FGA support," it almost always means a Zanzibar-derived ReBAC engine.
Common questions
What's the difference between FGA and ReBAC?
Which FGA product should I pick?
Do I need FGA if I have RBAC?