# Catch

A typed error channel for atoms and selectors.

Source: docs/source/concepts/catch.md
Packages: atom.io, atom.io/react
Related: loadable, selector, effect

The `catch` option declares how an atom or selector handles a known error type.

When a thrown value matches one of the constructors in `catch`, atom.io stores
that error as the state value instead of rethrowing it. Unmatched thrown values
still throw.

When a reactive value has a catch channel, code that observes it can understand
the handled error shape instead of treating every failure as unknown.

Use `catch` when asynchronous or effectful state has a meaningful error type
that downstream code should be able to inspect.