| --- |
| id: overview |
| title: Overview |
| --- |
| |
| TanStack Query (formerly known as React Query) is often described as the missing data-fetching library for web applications, but in more technical terms, it makes **fetching, caching, synchronizing and updating server state** in your web applications a breeze. |
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| ## Motivation |
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| Most core web frameworks **do not** come with an opinionated way of fetching or updating data in a holistic way. Because of this developers end up building either meta-frameworks which encapsulate strict opinions about data-fetching, or they invent their own ways of fetching data. This usually means cobbling together component-based state and side-effects, or using more general purpose state management libraries to store and provide asynchronous data throughout their apps. |
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| While most traditional state management libraries are great for working with client state, they are **not so great at working with async or server state**. This is because **server state is totally different**. For starters, server state: |
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| - Is persisted remotely in a location you may not control or own |
| - Requires asynchronous APIs for fetching and updating |
| - Implies shared ownership and can be changed by other people without your knowledge |
| - Can potentially become "out of date" in your applications if you're not careful |
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| Once you grasp the nature of server state in your application, **even more challenges will arise** as you go, for example: |
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| - Caching... (possibly the hardest thing to do in programming) |
| - Deduping multiple requests for the same data into a single request |
| - Updating "out of date" data in the background |
| - Knowing when data is "out of date" |
| - Reflecting updates to data as quickly as possible |
| - Performance optimizations like pagination and lazy loading data |
| - Managing memory and garbage collection of server state |
| - Memoizing query results with structural sharing |
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| If you're not overwhelmed by that list, then that must mean that you've probably solved all of your server state problems already and deserve an award. However, if you are like a vast majority of people, you either have yet to tackle all or most of these challenges and we're only scratching the surface! |
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| TanStack Query is hands down one of the _best_ libraries for managing server state. It works amazingly well **out-of-the-box, with zero-config, and can be customized** to your liking as your application grows. |
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| TanStack Query allows you to defeat and overcome the tricky challenges and hurdles of _server state_ and control your app data before it starts to control you. |
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| On a more technical note, TanStack Query will likely: |
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| - Help you remove **many** lines of complicated and misunderstood code from your application and replace with just a handful of lines of TanStack Query logic |
| - Make your application more maintainable and easier to build new features without worrying about wiring up new server state data sources |
| - Have a direct impact on your end-users by making your application feel faster and more responsive than ever before |
| - Potentially help you save on bandwidth and increase memory performance |
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| [//]: # 'Example' |
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| ## Enough talk, show me some code already! |
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| In the example below, you can see TanStack Query in its most basic and simple form being used to fetch the GitHub stats for the TanStack Query GitHub project itself: |
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| [Open in StackBlitz](https://stackblitz.com/github/TanStack/query/tree/main/examples/react/simple) |
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|
| ```tsx |
| import { |
| QueryClient, |
| QueryClientProvider, |
| useQuery, |
| } from '@tanstack/react-query' |
| |
| const queryClient = new QueryClient() |
| |
| export default function App() { |
| return ( |
| <QueryClientProvider client={queryClient}> |
| <Example /> |
| </QueryClientProvider> |
| ) |
| } |
| |
| function Example() { |
| const { isPending, error, data } = useQuery({ |
| queryKey: ['repoData'], |
| queryFn: () => |
| fetch('https://api.github.com/repos/TanStack/query').then((res) => |
| res.json(), |
| ), |
| }) |
| |
| if (isPending) return 'Loading...' |
| |
| if (error) return 'An error has occurred: ' + error.message |
| |
| return ( |
| <div> |
| <h1>{data.name}</h1> |
| <p>{data.description}</p> |
| <strong>👀 {data.subscribers_count}</strong>{' '} |
| <strong>✨ {data.stargazers_count}</strong>{' '} |
| <strong>🍴 {data.forks_count}</strong> |
| </div> |
| ) |
| } |
| ``` |
|
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| [//]: # 'Example' |
| [//]: # 'Materials' |
|
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| ## You talked me into it, so what now? |
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| - Consider taking the official [TanStack Query Course](https://query.gg?s=tanstack) (or buying it for your whole team!) |
| - Learn TanStack Query at your own pace with our amazingly thorough [Walkthrough Guide](../installation.md) and [API Reference](../reference/useQuery.md) |
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|
| [//]: # 'Materials' |
|
|
