TanStack/query

TanStack Query (formerly React Query) — server-state management library for web apps. The canonical "fetch + cache + refetch" library.

What it is

A TypeScript library that manages server state (data fetched from APIs) separately from client state. Provides caching, deduplication, background refetching, pagination, infinite queries, mutations with optimistic updates, and devtools. Framework-agnostic core with adapters for React, Vue, Svelte, Solid, Angular.

Key features

Caching, deduplication, stale-while-revalidate semantics.
Background refetching on window focus / network reconnect / interval.
Pagination + infinite scrolling helpers.
Mutations with optimistic updates + rollback.
Persistence (LocalStorage, IndexedDB) for offline.
Devtools for cache inspection.
Multi-framework: React, Vue, Svelte, Solid, Angular.
MIT-licensed.

Tech stack

TypeScript primary.
Framework adapters via separate packages (@tanstack/react-query, etc.).

When to reach for it

You're fetching server data and want caching + refetch logic out of the box.
You're replacing ad-hoc useEffect-based data fetching.
You want the canonical "server state" library.

When not to reach for it

All your state is client-only — use Zustand / Jotai / Redux.
You're at the smallest scale where plain fetch + useState is enough.

Maturity signal

Actively maintained under Tanner Linsley + the TanStack team. 5+ years.

Alternatives

SWR — comparable lighter alternative.
Apollo Client — GraphQL-specific.
RTK Query — for Redux-flavored.

Wiki: TanStack/query