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vercel/swr

📈 Trending★ 32,383TypeScriptAudience · developerComplexity · 2/5ActiveLicenseSetup · easy

TLDR

React hook library that fetches API data and caches it intelligently, showing stale data instantly while refreshing in the background for a snappy user experience.

Mindmap

mindmap
  root((SWR))
    What it does
      Fetches API data
      Caches automatically
      Updates in background
      Manages state
    Key features
      Revalidate on focus
      Offline detection
      Request deduplication
      Optimistic updates
    Use cases
      Real-time dashboards
      Live feeds
      Paginated lists
      Form submissions
    Tech stack
      React
      TypeScript
      Next.js compatible
      REST or GraphQL

Things people build with this

USE CASE 1

Build a real-time dashboard that refreshes data whenever the user returns to the browser tab.

USE CASE 2

Create a paginated product list that fetches new items as the user scrolls without managing loading states.

USE CASE 3

Show optimistic UI updates in a form so users see their submission succeed instantly before the server responds.

USE CASE 4

Fetch data from a GraphQL API with automatic caching and retry logic on network failures.

Tech stack

ReactTypeScriptNext.jsNode.js

Getting it running

Difficulty · easy Time to first run · 5min
Use freely for any purpose, including commercial use, as long as you keep the copyright notice.

In plain English

SWR is a React library that simplifies fetching data from APIs in your components. The name comes from "stale-while-revalidate," a caching strategy where the browser immediately shows previously fetched (stale) data from cache while simultaneously fetching a fresh copy in the background. Once the fresh data arrives, the component automatically updates. This makes your UI feel instant even on slow connections. The core of SWR is a single hook called useSWR. You give it a URL (or any unique key) and a fetcher function, an async function that makes the actual network request and returns the data. The hook handles all the state management automatically, giving back three values: the data itself, an error if something went wrong, and a loading flag while the request is in progress. Beyond the basic fetch-and-cache behavior, SWR adds a collection of behaviors that improve the user experience without any extra configuration. It automatically refetches data when the user switches back to the browser tab (revalidation on focus), when the network comes back online after going offline, or on a timer interval for real-time data. It deduplicates simultaneous requests for the same key so multiple components needing the same data only trigger one network call. It supports optimistic UI updates, showing the expected result immediately before the server confirms it, and has built-in pagination helpers and smart error retrying. You would use SWR in a React application whenever you need to load data from an API and keep it reasonably fresh without managing loading states, caching, and refetching logic yourself. It works well with Next.js (built by the same Vercel team), supports server-side rendering and static site generation, works in React Native, and is compatible with any data-fetching approach, REST, GraphQL, or anything else. The library is TypeScript-written, lightweight, and installable via npm.

Copy-paste prompts

Prompt 1
Show me how to use the useSWR hook to fetch user data from an API endpoint and display it in a React component.
Prompt 2
How do I set up SWR to automatically refetch data every 5 seconds for a live stock price ticker?
Prompt 3
Give me an example of using SWR with optimistic updates so a todo item appears checked before the server confirms the change.
Prompt 4
How do I use SWR to deduplicate requests when multiple components need the same data?
Prompt 5
Show me how to implement pagination with SWR using the offset and limit pattern.
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Generated 2026-05-18 · Model: sonnet-4-6 · Verify against the repo before relying on details.