recoil

Recoil is an experimental state management library for React developed by Facebook that provides a graph-based approach to shared state. Recoil introduces atoms — units of state that components can subscribe to — and selectors — pure functions that derive state from atoms or other selectors. When an atom's value changes, only components that subscribe to that specific atom re-render, providing fine-grained reactivity without context-based re-render cascading. Atoms are created with atom({ key: 'unique-key', default: initialValue }) and accessed in components with useRecoilState(myAtom) or useRecoilValue(myAtom). Selectors compute derived state asynchronously or synchronously: selector({ key: 'filtered', get: ({get}) => get(listAtom).filter(predicate) }). Recoil supports atom families for parameterized state (creating atom instances from a parameter), selector families for parameterized derived state, and snapshots for observing and time-traveling through state history. The library handles concurrent mode compatibility, which was a key motivation for its development at Facebook. While Recoil's development has slowed and its experimental status has led many teams to prefer Jotai (which offers a similar atomic model), Recoil's concepts have significantly influenced the React state management landscape.