# Fiber-local State

> Both the `FiberRef` and `ZState` data types are state management tools that are scoped to a certain fiber. Their values are only accessible within the fiber that runs them.

Both the `FiberRef` and `ZState` data types are state management tools that are scoped to a certain fiber. Their values are only accessible within the fiber that runs them.

We have a separate page for the [`FiberRef`](fiberref.md) and [`ZState`](zstate.md) data types which explain how to use them.