React 18 vs React 19: Boosting Rendering Performance

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React 18 vs React 19: Boosting Rendering Performance

Quick Summary

This blog compares React 18 and React 19, focusing on how the latter improves performance and reduces costs for businesses. React 19 introduces automatic concurrent rendering and fully integrated React Server Components, offering smoother user experiences and better scalability. It eliminates the need for manual configurations, making apps faster, reducing server costs, and enhancing user retention. Businesses can benefit from these improvements through faster load times, smaller bundles, and simplified development.

Introduction:

React has come a long way, and with React 19, there are some exciting improvements, especially in how it handles rendering. But what does that actually mean for businesses? In this blog, we’ll explore how these changes can help reduce costs and create better experiences for your users. If you’ve been wondering whether upgrading from React 18 to React 19 is worth it, this is the place to start! For businesses looking to leverage the power of React 19 and improve app performance, working with a trusted React JS development company can ensure a smooth and efficient transition.

Problem Analysis

Slower Performance for Complex Apps: For apps with lots of interactive or complex components, React 18 sometimes struggled to keep things running smoothly. This could lead to delays in updating the UI, which wasn’t great for users.
Higher Costs: React 18 wasn’t always efficient with how it used resources, meaning businesses often had to spend more on servers and infrastructure to keep their apps performing well — especially during high-traffic times.
Frustrated Users: When an app feels slow or clunky, users notice. Even small delays in React 18’s rendering could leave users feeling frustrated, which isn’t good for keeping them engaged or happy.

To understand how React 19 improves rendering, let’s dive into practical examples highlighting its enhancements.

What is Concurrent Rendering?

Concurrent rendering allows React to handle multiple tasks at once, without blocking the user interface. It ensures that user interactions, like typing, scrolling, or clicking, are prioritized and handled quickly, while background tasks, like data fetching or complex calculations, can run concurrently without freezing the UI.

In React 18, concurrent rendering was experimental, and developers had to manually opt into features like useTransition or startTransition to make certain tasks less urgent and prioritize others. It was useful, but developers had to manage it more carefully.

Here’s an example of how you would set up concurrent rendering in
React 18:

import React, { useState, useTransition } from 'react';
const SearchList = ({ data }) => {
const [query, setQuery] = useState('');
const [isPending, startTransition] = useTransition();
const handleChange = (e) => {
startTransition(() => {
setQuery(e.target.value); // This operation is treated as low priority in React 18
});
};
const filteredData = data.filter(item => item.includes(query));
return (
<div>
<input
type="text"
value={query}
onChange={handleChange}
placeholder="Search..."
/>
{isPending && <p>Loading...</p>}
<ul>
{filteredData.map((item, index) => <li key={index}>{item}</li>)}
</ul>
</div>
);
};
export default SearchList;

In React 18, we used startTransition to mark the state update as a lower priority, so it wouldn’t block more important tasks like typing in the search bar. While effective, it required manual control.

React 19 automatically manages concurrent rendering. Unlike React 18, there is no need for manual transitions or hooks like useTransition. React 19 can prioritize user interactions (like typing, clicking) over less critical tasks (like filtering data or fetching resources). This means less boilerplate code and smoother performance right out of the box.

In React 19:

import React, { useState } from 'react';
const SearchList = ({ data }) => {
const [query, setQuery] = useState('');
const handleChange = (e) => {
setQuery(e.target.value); // Automatically treated as high priority in React 19
};
const filteredData = data.filter(item => item.includes(query));
return (
<div>
<input
type="text"
value={query}
onChange={handleChange}
placeholder="Search..."
/>
<ul>
{filteredData.map((item, index) => <li key={index}>{item}</li>)}
</ul>
</div>
);
};
export default SearchList;

Why React 19’s Concurrent Rendering is Better for Businesses

Smoother User Experience: React 19 automatically prioritizes user actions, making your app feel instant and responsive, even when performing complex tasks in the background.
Better Performance at Scale: As your app grows, React 19 can handle more updates without slowing down, improving user retention and satisfaction.

What are React Server Components?

React Server Components allow you to render parts of your React component tree on the server and send only the minimal HTML and data to the client, improving performance.

In React 18, Server Components were introduced but still in experimental stages. You had to manually enable them by using certain flags and features. React 18 allowed Server Components to fetch data from a server and render it, but it wasn’t as integrated or easy to use as in React 19.

In React 18:

// App.js - Client-side component
import React, { Suspense } from 'react';
import { fetchUserData } from './server';
const UserProfile = React.lazy(() => fetchUserData());
function App() {
return (
<div>
<h1>Welcome to our App</h1>
<Suspense fallback={<div>Loading...</div>}>
<UserProfile />
</Suspense>
</div>
);
}
export default App;
// server.js - Server-side code to fetch data
export const fetchUserData = async () => {
const data = await fetch('https://api.example.com/user');
return data.json();
};

In React 19, Server Components are now fully integrated and automatic. React 19 has improved how Server Components interact with both the server and client. It eliminates the need for manual setup like in React 18, making it easier to use while ensuring better performance and smoother user experience.

In React 19:

// App.js - Client-side component (with automatic Server Components)
import React from 'react';
import { UserProfile } from './server';

function App() {
return (
<div>
<h1>Welcome to our App</h1>
<UserProfile />
</div>
);
}

export default App;

// server.js - Server-side component rendering
export const UserProfile = () => {
// Fetch data directly inside the component
const data = fetchDataFromServer(); // Automatically handled in React 19
return <div>{data.username}</div>;
};

async function fetchDataFromServer() {
const response = await fetch('https://api.example.com/user');
const data = await response.json();
return data;
}

In React 19, you no longer need React.lazy or Suspense for Server Components. React automatically determines which components need to be rendered server-side and handles the entire flow more efficiently. This leads to simplified code and better performance without extra configuration.

Why React 19’s Server Components Benefit Businesses

Faster Load Times: React 19 pre-renders UI on the server for a faster user experience.
Smaller Bundles: Reduces JavaScript on the client side, speeding up apps, especially on mobile.

Conclusion:

In short, React 19 makes apps faster and smoother with automatic concurrent rendering and seamless server-side rendering. These upgrades reduce costs, improve performance, and simplify development. For businesses aiming to enhance their applications, partnering with a trusted React JS development company can help you fully leverage the benefits of React 19, ensuring better user experiences and more efficient apps.

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