React vs Angular Performance

Published on November 6th, 2024

React and Angular are two of the most reliable frameworks for building web applications. When choosing between React and Angular as the right framework for your web application, PERFORMANCE is a crucial factor. React leverages virtual DOM to outperform in its rendering efficiency. It achieves this while reducing costly DOM updates. On the other hand, Angular uses DOM manipulation and two-way data binding. It offers optimization options, like Ahead-Of-Time (AOT) compilation and change detection strategies. Both Angular and React can handle large datasets. 

In this blog, we will uncover React vs Angular performance-based differences, with a focus on aspects, like rendering, change detection, handling of large data sets, and overall scalability in real-world scenarios. 

React vs Angular Performance – Detailed Comparison 

When it comes to making a choice between React and Angular based on their performance, there are notable differences between the two, which are discussed below: 

1. Rendering Performance

React 

React uses virtual DOM to efficiently update and render changes. It reduces re-rendering, which makes it fast for dynamic applications. 

• Virtual DOM – Virtual DOM (Document Object Model) is a lightweight copy of the real DOM. React uses this virtual DOM to make updates more efficient. Instead of updating the entire real DOM, React compares the virtual DOM to the real one and finds only the parts that need changes. This process, called “diffing”, reduces the direct number of direct DOM manipulations, which are usually slow and resource-heavy. This approach helps React improve its performance by speeding up updates and rendering. 
• Component Rendering – React needs to re-render components when states or props change. However, to improve performance, React can avoid unwanted re-renders using tools like shouldComponentUpdate or React.memo function. These tools ensure React only updates the components when needed to free the app from consuming unnecessary resources and wasting them on repetitive updates.
• Example: In an app with heavy user interface, React minimizes repainting through a virtual DOM. The diffing process only renders the part of the UI that needs it, which helps to keep performance high even with frequent UI updates.

Angular 

Angular interacts with real DOM directly, making it slower. However, it uses pre-compilation to speed up rendering in the beginning. 

• Real DOM – Angular uses the real DOM, so whenever there’s a change, it actually updates the actual structure of the webpage. But that means every update will slow down performance if the application grows bigger or changes more frequently — all because the whole DOM must be refreshed every time. Hence, it’s less efficient than other frameworks that use virtual DOM.
• Ahead-of-Time (AOM) Compilation – Angular uses AOT compilation, which means it pre-compiles, HTML, and TypeScript code before the browser runs it. It allows the browser to do less work, making it render faster at runtime. By reducing the time the browser has to spend compiling, AOT makes the whole Angular application run faster and quicker.
• Example: Angular’s AOT compilation can speed up initial load for both static and lightweight (less often DOM updated) applications. Unfortunately, the performance may decline when the complexity grows from direct DOM manipulation.

Summary: 

2. Change Detection 

React 

React updates components only when state or props change. This enables control and prevents unnecessary updates, improving performance.

• State-based Rendering – Components are re-rendered in React only when the state or props change. This behavior allows developers to control exactly when and how components are updated, expanding the control traditionally granted to them. This enhanced control helps improve performance by reducing unnecessary renders. 
• Optimization Techniques: Developers can use React’s hooks, such as useMemo or useCallback to memorize values and functions, reducing unnecessary renders. This can be really useful in large applications where the rendering cycles cause performance bottlenecks.

Angular 

Angular frequently checks the entire app for changes, which can slow down the performance. However, developers can optimize this behavior using: 

• Two-Way Data Binding – Angular uses two-way data binding where changes made to the UI automatically update the model, and vice versa. This causes the application to do more frequent checks to verify everything stays in sync. Angular’s change detection is based on zones, which monitor every asynchronous operation, like user input or HTTP requests, etc., and perform a full application check every time to ensure that the updates are real-time and accurate.
• Optimization Techniques: Developers can use the OnPush change detection strategy to optimize Angular. This strategy limits checking to just those components whose data has changed and avoids performance overhead resulting from lots of change detection in large applications.

Also, read: Angular Vs React Vs Vue: Which One To Choose

3. Handling Large Data Sets

React 

It uses data virtualization to render large lists efficiently. It only renders what’s visible, which improves performance in large applications. 

• Virtualization: React provides great support for data virtualization with libraries like react-window and react-virtualized. These tools render the items that are currently visible on the screen, making it easier to manage and display large data sets without slowing down performance. React improves efficiency and responsiveness by reducing the number of rendered elements at a time, particularly for apps handling lots of data. 
• Example: 

When displaying 10,000 items in an app, React can render just the ones we see now and load more as we scroll. It neatly minimizes memory used and still allows smooth scrolling with large data sets.

Angular 

Angular uses a tracking system to handle large amounts of data. However, its change detection can slow down the process, if not optimized.

• Track-by Function – Angular is great for dealing with large lists, thanks to features such as ngFor and trackBy which help minimize unnecessary renders by better tracking items. But if you are working with large data sets, performance issues can still occur because Angular runs its change detection, which scans the entire component tree for change. This can cause slower performance, especially with heavy data processing in complex applications.
  
  However, with Angular 17, performance in handling large lists has improved through optimized reactivity. The updated @angular/signals API reduces change detection overhead by making Angular more selective in tracking data changes, which cuts down on unnecessary re-renders. This enhancement helps streamline performance in data-heavy applications.

4. Bundle Size and Load Times 

React

It is lightweight with a smaller bundle size, which results in faster loading times. It uses tree shaking to remove unused code. 

• Tree Shaking –  It is a way for React’s bundlers, such as Webpack, to automatically remove any unused code from your project, thus reducing the total bundle size. React is a lightweight library, so its size is only around 42.5 KB when minified and zipped. Thus, it helps to speed up loading time, especially on large applications that have a complex codebase. It speeds up the app experience for users and improves it.
• Example: A small bundle size on a minimal React app means a quick initial load. Combined with lazy loading techniques, large parts of the app can be loaded only when needed.

Angular 

The bundle size of Angular is larger, but the initial load time is reduced with AOT and lazy loading

• Heavier Framework: Angular is a complete framework with a large bundle size, around 500Kb (minified & zipped). This makes it heavier than other solutions. But with features like Ahead of Time (AOT) compilation and lazy loading, Angular Command Line Interface (Angular CLI) can significantly reduce the initial load time by loading only needed resources at a time, making it better for large applications.
• Optimization example: The size of the code needed at the runtime can be reduced by using Angular’s AOT, which pre-compiles the code. Although Angular’s larger size can slow down the performance initially, strategic use of lazy loading can reduce some of the load-time penalties. 

Important article: React vs Angular: Which JS Framework is best for Front-end Development?

5. Performance in Large-Scale Applications 

React

It is well-suited for large, dynamic applications. It delivers strong performance with complex state management and efficient updates. 

• Scalability: React is an ideal option for frequently evolving apps. It makes use of efficient state management tools like Redux and MobX, which help manage data and application state. So, if your app becomes more complex with many features and components, React tends to perform well. With proper planning, React can offer a great user experience, even if your app grows bigger. 

• Example: A large e-commerce app built using React.js can handle thousands of products in real-time without compromising performance. Thanks to React’s virtual DOM and efficient state management. 

Angular

It is designed for enterprise-level applications. However, its change detection needs to be optimized for large-scale apps.

• Enterprise-Level Performance – Angular can easily support large-scale enterprise applications due to its strong architecture that can manage heavy and complex workloads. However, as the application size increases, its change detection mechanism needs to be carefully optimized. Without proper optimization, this can cause performance issues, which can slow down the app and affect its responsiveness, particularly in data-heavy applications.

6. Server-Side Rendering

React

Frameworks like Next.js can allow React to integrate well with server side rendering. In SSR, React renders the content on the server and then sends the HTML to the client. This approach speeds up the initial load times, particularly for SEO-sensitive apps in which page indexing is a must. If the initial server rendered HTML is already loaded, then React’s virtual DOM makes sure, that the updates to the DOM are quick.

Example: By preloading data and rendering it server-side, Next.js improves SSR performance for React apps, as users spend less time waiting for the first-page load.

Angular 

Angular supports SSR with Angular Universal, but that pre-renders pages on the server. This process makes Angular applications faster for the user by reducing client-side rendering time (which is invaluable in case of applications with dynamic content). Angular’s larger bundle size, though, means that SSR is more resource intensive, so it can impact performance too if it isn’t handled well. While AOT and lazy loading can’t fully eliminate initial load times, Angular Universal can still make good use of it to enhance initial load times as well as SEO rankings.

Example: With Angular Universal, an Angular-based e-commerce site can achieve quick server-rendered load times for improved SEO and user experience, still requiring some performance optimizations for large and dynamic content updates.

Also, read: React vs Vue: Comparison of the Best JavaScript Frameworks in 2024

The Verdict

When focusing entirely on performance: 

• React outperforms Angular in rendering efficiency, especially with frequent UI updates. Thanks to its virtual DOM and control over re-renders.  
• Angular is better optimized for static or less interactive apps with less frequent updates, though its performance can be enhanced through techniques like AOT and OnPush.  

In short, React is optimal for high-interactivity, while Angular is solid for stable, feature-rich applications with fewer real-time changes.