React Query vs SWR: Choosing the Right Data Fetching Library for Your React Applications

When it comes to managing server state in React applications, developers often find themselves with a couple of popular contenders: React Query and SWR. Both libraries provide efficient ways to fetch, cache, and sync data in your applications, but they do so with slightly different philosophies and features. In this article, we’ll take a deep dive into React Query and SWR, comparing their key features, use cases, and performance to help you make an informed decision.

Understanding Server State Management

Before we get into the nitty-gritty of these libraries, it’s important to understand what server state management is. Unlike local state that can be managed within a component using React’s own state management tools, server state involves data that comes from an API or server. This data often has a lifecycle that may or may not be directly tied to the component lifecycle, which adds complexity to how we manage it.

What is React Query?

React Query is an open-source library developed by Tanner Linsley that helps manage data fetching, caching, and synchronization in React applications. It aims to simplify the process of fetching data and provides several powerful features that boost the performance and user experience of web applications.

Core Features of React Query

• Automatic Caching: React Query caches responses from the server, reducing the number of requests made and speeding up the application’s responsiveness.
• Smart Refetching: It automatically refetches data in various scenarios, like when the window is refocused or when the user reconnects to the internet.
• Query Invalidation: You can invalidate specific queries and refetch them as needed, making it easy to keep the UI in sync with the server state.
• Mutation Support: React Query offers a robust API for handling data mutations, providing options for optimistic updates and rollbacks.
• Devtools: A useful set of development tools that help monitor and debug queries in real-time.

Example Code with React Query

Let’s take a quick look at how you can implement React Query in your application:

import { useQuery } from 'react-query';

function fetchTodos() {
    return fetch('https://jsonplaceholder.typicode.com/todos')
        .then(res => res.json());
}

function TodoList() {
    const { isLoading, error, data } = useQuery('todos', fetchTodos);

    if (isLoading) return <p>Loading...</p>;
    if (error) return <p>An error occurred: {error.message}</p>;

    return (
        <ul>
            {data.map(todo => <li key={todo.id}>{todo.title}</li>)}
        </ul>
    );
}

What is SWR?

SWR, which stands for “stale-while-revalidate,” is a data fetching library created by Vercel for React applications. It is designed to provide a simpler API to handle data fetching, caching, and revalidation with an emphasis on performance and user experience. The name “stale-while-revalidate” is derived from HTTP caching strategies, indicating that cached data can be returned while new data is fetched in the background.

Core Features of SWR

• Optimistic Updates: By the time the data is being fetched, users can see the old data, providing a smoother experience.
• Automatic Revalidation: SWR refetches data automatically on window focus and network reconnection.
• Flexible Error Handling: It provides a fine-grained control over error handling, making it easy to show errors at the appropriate places in your UI.
• Cache Invalidations: You can easily invalidate specific caches using various commands.
• Simple API: A streamlined API enables quick setups and straightforward data fetching logic.

Example Code with SWR

Here’s how you can use SWR to fetch data:

import useSWR from 'swr';

const fetcher = url => fetch(url).then(res => res.json());

function TodoList() {
    const { data, error } = useSWR('https://jsonplaceholder.typicode.com/todos', fetcher);

    if (error) return <p>An error occurred: {error.message}</p>;
    if (!data) return <p>Loading...</p>;

    return (
        <ul>
            {data.map(todo => <li key={todo.id}>{todo.title}</li>)}
        </ul>
    );
}

Comparing React Query and SWR

Now that we have a basic understanding of each library, let’s compare their strengths and weaknesses.

Ease of Use

SWR provides a very lightweight API, which makes it quicker to get started with. If you need a simple fetching mechanism, SWR might be the way to go. React Query, while also fairly simple, has a broader API with more options which can initially overwhelm new users.

Data Mutations

React Query shines with its support for data mutations, offering extensive hooks for handling POST, PUT, DELETE requests, and optimistic updates. SWR does support mutations, but developers generally find React Query’s methods to be more capable and robust.

Caching and Revalidation

Both libraries offer excellent caching strategies. React Query’s caching is more configurable, allowing for advanced use cases, while SWR focuses on the “stale-while-revalidate” approach for returning cached data instantly while asynchronously fetching new data.

Performance

Both libraries are optimized for performance, but React Query’s ability to batch network requests and manage them efficiently can give it an edge in larger applications with complex data requirements.

Development Tools

React Query’s Devtools give developers a deeper understanding of cache management, making it easier to debug issues effectively. However, SWR lacks built-in development tools, requiring additional tooling or logging for monitoring.

Use Case Scenarios

When to Choose React Query

• Your application involves a lot of data mutations.
• There’s a need for in-depth caching and revalidation controls.
• You prefer a rich set of hooks and options for managing queries and mutations.

When to Choose SWR

• You are building a simple application that requires moderate data fetching.
• You value a quick and minimal setup.
• Your main focus is to reduce bundle size and use optimized fetching strategies.

Conclusion

Both React Query and SWR have their strengths and weaknesses. The choice between them largely depends on the complexity of your data-fetching needs and personal or team preferences. For simple applications, SWR can be the right choice for its lightweight nature, while React Query is perfect for more complex applications that require a richer set of functionalities.

Ultimately, testing both libraries in small projects may provide valuable insights into which fits best within your development workflow.

Happy coding!