React Query Library's Broadcast Query Client: Real-Time Sync Across Browser Tabs

Anton Ioffe - March 2nd 2024 - 10 minutes read

In the ever-evolving landscape of modern web development, engineering seamless user experiences across multiple browser tabs has long been a challenge that developers have strived to overcome. Enter the React Query Library's Broadcast Query Client, a powerful tool designed to revolutionize how we approach data synchronization and state management in React applications. This article will take you on a deep dive into the capabilities and applications of the Broadcast Query Client, offering a comprehensive guide to harnessing its potential for real-time data sync across tabs. From technical insights and real-world implementation to performance optimization and common pitfalls, we'll explore the intricacies of this feature through a lens that balances technical depth with actionable guidance. Prepare to unlock new possibilities in creating dynamic, user-friendly web applications that speak the same language across all open tabs, seamlessly.

The Role of React Query in Modern Web Development

React Query represents a significant leap forward in handling data fetching and state management within React applications. At its core, this library simplifies dealing with asynchronous data flows, enabling developers to focus on building their applications without getting bogged down by the intricacies of data synchronization and caching mechanisms. Unlike global state management solutions that often require developers to manually handle data fetching, caching, and state updates, React Query abstracts these concerns away. It offers a streamlined workflow where data fetching, caching, and synchronization are managed automatically, reducing the need for boilerplate code and enhancing application performance.

One of React Query's strengths lies in its client-side approach to data management. This strategy diverges significantly from traditional methods that rely heavily on global state management libraries. Instead of maintaining a global state that requires manual updating and synchronization across components, React Query manages server state locally within components. This local management allows for more granular control over data fetching and caching, ensuring that components only re-render when the data they depend on changes. Consequently, applications become more efficient and responsive, providing a better user experience.

React Query's architecture is particularly adept at dealing with complex data scenarios such as pagination, infinite scrolling, and optimistic updates. It eliminates the need for developers to implement these features manually, which not only speeds up development time but also reduces the likelihood of bugs. By abstracting away the complexity involved in managing asynchronous data operations, React Query enables developers to implement complex data interactions with ease, resulting in cleaner and more maintainable code.

Furthermore, React Query enhances data reliability and user experience through features like automatic background refetching, data prefetching, and query invalidation. These features ensure that applications are always displaying the most up-to-date information without requiring user intervention. Automatic background refetching keeps data fresh by periodically fetching data in the background, prefetching allows for faster loading times by fetching data before it's needed, and query invalidation enables developers to mark stale data, ensuring that it gets refreshed on the next query.

In conclusion, React Query revolutionizes how React developers handle data fetching and state management by providing a comprehensive, client-side solution. It strips away much of the complexity associated with asynchronous data management, allowing developers to focus more on creating engaging and dynamic user experiences. With its automatic data synchronization, efficient caching mechanisms, and support for complex data interactions, React Query stands out as an essential tool in the modern web development landscape, particularly for those looking to build data-rich and highly interactive React applications.

Introduction to Broadcast Query Client

The Broadcast Query Client feature in React Query represents a seminal shift towards ensuring real-time synchronization of application state across multiple browser tabs, a scenario increasingly common in today's web applications. At its core, this feature leverages the modern web's Broadcast Channel API, creating a pub-sub (publish-subscribe) mechanism whereby instances of an application in different tabs can communicate changes to each other seamlessly. This mechanism is especially pertinent in scenarios where an application's state changes need to be reflected instantly across all instances, enhancing the user experience by keeping the application state consistent and up-to-date without manual refreshes.

Understanding the underlying technology, the Broadcast Channel API provides a way for JavaScript contexts sharing the same origin to broadcast messages to each other. React Query's Broadcast Query Client harnesses this API to broadcast invalidations and data updates across browser tabs, thus ensuring that any mutations or query invalidations in one tab are communicated and reflected in all other open tabs. This is a step forward in building dynamic, user-friendly web applications that react in real time to user interactions and data changes, regardless of the tab being currently viewed.

The significance of this feature cannot be overstated in the context of modern web development, where user experience often dictates the success of an application. In a typical multi-tab usage scenario without the Broadcast Query Client, users would need to manually refresh tabs to see updates, leading to a disjointed and frustrating experience. With the introduction of this feature, developers can ensure that their applications remain lively and engaging, responding instantly to changes and interactions in any tab, thereby significantly enhancing the overall user experience.

Moreover, implementing the Broadcast Query Client in an application is a forward-thinking decision, not just for enhanced synchronization but also because it taps into advanced browser capabilities while maintaining a graceful fallback for browsers where the Broadcast Channel API is not supported. This ensures wide compatibility and reliability across different user agents, making applications robust and future-proof.

In conclusion, the Broadcast Query Client feature of React Query is a powerful tool that bridges the gap between the capabilities of modern browsers and the expectations of today's web users for real-time responsiveness. By enabling seamless state synchronization across browser tabs, it opens up new avenues for creating dynamic, engaging, and highly responsive web applications. Its reliance on the Broadcast Channel API underpins a broader shift towards leveraging browser-native capabilities for enriching the web development ecosystem, making it an essential consideration for web developers aiming to elevate the user experience in their applications.

Implementing Broadcast Query Client in a Real-World Scenario

First, ensure React Query is installed in your project. If it’s not, run npm install react-query in your project directory. This library will manage your server state and cache out of the box, but to enable real-time sync across browser tabs, we'll bring into play the Broadcast Query Client functionality.

Initializing the React Query library in your project starts with wrapping your application in a QueryClientProvider component. This requires creating a QueryClient instance and passing it to the provider. To facilitate broadcasting updates, you must configure the QueryClient with a custom broadcastQueryClient method. This method intercepts query mutations and broadcasts them to other tabs.

import { QueryClient, QueryClientProvider, broadcastQueryClient } from 'react-query';

const queryClient = new QueryClient();
queryClient.setQueryDefaults('*', {
  broadcastQueryClient: true,

function App() {
  return (
    <QueryClientProvider client={queryClient}>
      {/* Your application components go here */}

To demonstrate real-time synchronization, let’s create a simple feature: a shared to-do list. Any addition or removal of a to-do item in one browser tab should reflect across all other open tabs instantly. Implementing this starts with utilizing the useQuery hook to fetch and display the to-do list and the useMutation hook for adding or removing items, ensuring these changes are automatically broadcasted to all tabs.

function TodoList() {
  const { data: todos } = useQuery('todos', fetchTodoList);
  const mutation = useMutation(addTodo, {
    onSuccess: () => {

  return (
      { => (
        <p key={}>{todo.text}</p>
      <button onClick={() => mutation.mutate({ text: 'New Todo' })}>Add Todo</button>

In this code, fetchTodoList is a function responsible for fetching the list of todos from your server, and addTodo is a function that adds a new todo item. After a mutation succeeds, queryClient.invalidateQueries('todos') ensures the query for todos is marked as stale. Since we configured the query client with broadcastQueryClient: true, this invalidation, and thus the refetching of the todos, happens across all browser tabs.

In conclusion, integrating the Broadcast Query Client with React Query in your application allows for seamless synchronization of user data across multiple tabs, enhancing the user experience by keeping the application state consistent everywhere. By following the steps outlined above and leveraging the power of React Query’s real-time capabilities, developers can build more interactive and dynamic web applications.

Performance Considerations and Best Practices

React Query's Broadcast Query Client possesses a unique capability of synchronizing state across browser tabs, significantly enhancing user experience by ensuring real-time data freshness. However, it's crucial to consider the impact on application performance, particularly in regard to memory usage and network efficiency. The continuous syncing process, while beneficial for user experience, can potentially lead to increased memory usage and network traffic, as data updates are broadcasted across all opened tabs. It's important to implement efficient query caching strategies to mitigate these risks. Proper cache invalidation plays a crucial role here, ensuring that only necessary data is refetched and updated, thereby minimizing unnecessary memory and network resource usage.

Optimizing the usage of the Broadcast Query Client involves a delicate balance between performance and real-time data accuracy. Developers should leverage React Query's built-in mechanisms such as staleTime and cacheTime configurations to control the behavior of caching and data fetching more finely. Setting an appropriate staleTime can significantly reduce the number of unnecessary re-fetches by allowing the data to be considered fresh for longer periods, which in turn reduces the load on the server and the network traffic. Similarly, adjusting cacheTime helps in managing memory usage by defining how long unused data should be kept in memory before being garbage collected.

To avoid potential performance bottlenecks, it's also critical to structure queries with a keen eye on what data is essential and how often it needs to be updated. Utilizing techniques like query bundling or pagination to fetch data can alleviate the strain on both the client and server by reducing the size of the data payload and the frequency of updates required. In scenarios where data changes are frequent and voluminous, considering a strategy for partial updates or deltas might be necessary to efficiently update clients with only the changed data, rather than resending the entire dataset.

An often overlooked aspect of using React Query, especially with the Broadcast Query Client, is the seamless incorporation of prefetching strategies. Prefetching data that the user is likely to interact with next can significantly enhance the experience by reducing loading times. React Query's prefetchQuery method can be adeptly used to load data in the background, anticipating user actions based on their current context within the application. This proactive approach can greatly smooth out data loading phases, contributing positively to the perceived performance of the application.

In conclusion, while the Broadcast Query Client from React Query opens up new possibilities for real-time state synchronization across browser tabs, it introduces several performance considerations that require careful management. By strategically caching data, efficiently managing re-fetches, structuring queries thoughtfully, and employing prefetching where beneficial, developers can harness the power of this tool without compromising on application performance. Balancing these factors effectively will not only ensure a responsive and engaging user experience but also maintain application scalability and resource efficiency.

Common Pitfalls and How to Avoid Them

One frequent mistake developers encounter with React Query's Broadcast Query Client is improper query invalidation. This often happens when developers either forget to invalidate queries after a mutation or do so in an incorrect manner, leading to stale data persisting across tabs. The correct approach involves explicitly invalidating queries that are affected by mutations, ensuring that data remains fresh and consistent across all browser tabs.

// Incorrect approach
function addTodoIncorrect() {
    return addTodoApi().then(() => {
        // Missing query invalidation

// Correct approach
function addTodoCorrect() {
    return addTodoApi().then(() => {

Another common pitfall is an over-reliance on React Query's default configuration without applying necessary customizations for the application's specific needs. For instance, the default stale time might not be appropriate for all data types, leading to either too frequent or too infrequent data fetching. Developers should tailor React Query settings, such as staleTime and cacheTime, to fit their application's requirements.

// Customization for more frequent updates
const todosQuery = useQuery('todos', fetchTodos, {
    staleTime: 5 * 1000, // data is considered stale after 5 seconds

Misunderstanding synchronization principles can also lead to issues, especially when developers expect Broadcast Query Client to manage all state synchronization automatically without consideration for client-specific state. While React Query efficiently synchronizes server state, client-side state requires manual intervention for syncing across tabs.

Developers sometimes mistakenly use queryClient.setQueryData for optimistic updates without considering the implications for multi-tab scenarios. Without proper rollback strategies or query invalidation, this can lead to inconsistent app states. A more reliable approach involves using React Query's onMutate and onSettled options within mutations to handle optimistic updates and potential rollbacks coherently.

// Mistake: Optimistic update without considering multi-tab consistency
mutate(addTodo, {
    onMutate: async newTodo => {
        queryClient.setQueryData('todos', old => [...old, newTodo]);

// Improved approach ensuring consistency
mutate(addTodo, {
    onMutate: async newTodo => {
        await queryClient.cancelQueries('todos');
        const snapshot = queryClient.getQueryData('todos');
        queryClient.setQueryData('todos', old => [...old, newTodo]);
        return { snapshot };
    onError: (err, newTodo, context) => {
        queryClient.setQueryData('todos', context.snapshot);
    onSettled: () => {

Lastly, neglecting to consider error handling across tabs is a pitfall that can degrade the user experience. Implementing a global error handling strategy, such as using React Query's useErrorBoundary in tandem with a coherent application-wide error management approach, ensures that users receive consistent feedback and support, regardless of the tab they are interacting with.

By addressing these common pitfalls with informed strategies and best practices, developers can leverage React Query's Broadcast Query Client to build robust, real-time applications that deliver a consistent and engaging user experience across all browser tabs.


The article explores the capabilities and applications of the React Query Library's Broadcast Query Client, which enables real-time data synchronization across browser tabs in React applications. It discusses the benefits of using React Query for data fetching and state management, the technical implementation of the Broadcast Query Client, performance considerations, and common pitfalls to avoid. The key takeaway is that by implementing the Broadcast Query Client, developers can create dynamic and user-friendly web applications with seamless synchronization across tabs. A challenging technical task for the reader would be to implement the Broadcast Query Client in their own real-world scenario and optimize its performance by utilizing caching strategies and prefetching techniques.

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