SSR vs CSR vs Pre-rendering in React JS: Which Is Better?

Understanding ‘SSR vs CSR vs Pre-rendering in React JS’ is crucial for optimizing web performance and improving user experiences. These techniques solve issues like slow page loads, poor SEO, and increased server load. Intrigued? Keep reading to discover how mastering these concepts can enhance your React JS applications for both developers and users alike.

What Is Rendering in React JS?

Rendering in React JS refers to the process of displaying UI components on the browser screen. Whenever data changes in a React application, React updates the user interface by rendering components again.

In simple terms, rendering means converting React components into HTML that users can see and interact with in the browser.

React uses a Virtual DOM to improve performance. Instead of updating the entire webpage, React compares changes in the Virtual DOM and updates only the required parts of the actual DOM.

How React Displays Content in Browsers

React applications typically start with a root HTML file containing a single <div> element:

<div id="root"></div>

React then injects components into this root element using JavaScript.

Example:

import React from "react";
import ReactDOM from "react-dom/client";
import App from "./App";

const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(<App />);

Here’s what happens step-by-step:

1. Browser loads the HTML file
2. JavaScript bundle is downloaded
3. React executes the code
4. Components are converted into HTML
5. Content appears on the screen

Difference Between Server and Browser Rendering

Feature	Server Rendering	Browser Rendering
Rendering Location	Server	User’s Browser
Initial Load Speed	Faster	Slower
SEO Performance	Excellent	Weak
JavaScript Dependency	Less	High
User Experience	Faster first view	Better app-like interactions

In server rendering, the server sends fully generated HTML to the browser. In browser rendering, JavaScript creates the page after loading.

What Is CSR (Client-Side Rendering)?

Client-Side Rendering (CSR) is a rendering method where the browser downloads JavaScript first and then generates the webpage content on the client side.

React applications created using tools like Vite or Create React App mainly use CSR.

Definition of CSR

In CSR, the server sends a minimal HTML file along with JavaScript bundles. React runs inside the browser and dynamically builds the UI.

The browser is responsible for rendering the content instead of the server.

How CSR Works Step-by-Step

1. User requests a webpage
2. Server sends basic HTML and JavaScript files
3. Browser downloads JavaScript bundles
4. React executes in the browser
5. Components render dynamically
6. Page becomes interactive

React SPA Architecture

CSR is commonly used in Single Page Applications (SPAs).

In an SPA:

• Only one HTML page is loaded initially
• Navigation happens without full page refreshes
• React updates components dynamically

Popular examples include:

• Gmail
• Trello
• Notion

CSR Rendering Flow Diagram

User Request
      ↓
Server Sends Empty HTML + JS Bundle
      ↓
Browser Downloads JavaScript
      ↓
React Executes in Browser
      ↓
UI Generated Dynamically
      ↓
Interactive Webpage Displayed

Example Using Vite

Create a React App with Vite

npm create vite@latest my-app
cd my-app
npm install
npm run dev

Example Component

function App() {
  return <h1>Welcome to CSR in React</h1>;
}

export default App;

The content is rendered entirely inside the browser after JavaScript loads.

Pros of CSR

• Fast Client-Side Navigation
  After the first load, navigation between pages becomes very fast because only component data changes instead of reloading entire pages.
• Better Interactive UX
  CSR provides smooth interactions, animations, and real-time updates, making applications feel more like native apps.
• Reduced Server Load
  The server mainly delivers static assets, reducing rendering work on the backend.

Cons of CSR

• Poor SEO
  Search engines may struggle to index JavaScript-generated content properly, especially if rendering fails.
• Slower First Contentful Paint
  Users may initially see a blank page while JavaScript loads and executes.
• Blank Screen Issue on Slow Devices
  Heavy JavaScript bundles can delay rendering on low-end devices or slow internet connections.

Best Use Cases for CSR

• Dashboards
  Applications with highly interactive interfaces and authenticated users.
• SaaS Apps
  Tools like project management systems or CRMs benefit from CSR responsiveness.
• Admin Panels
  Admin dashboards often prioritize interactivity over SEO.

What Is SSR (Server-Side Rendering)?

Server-Side Rendering (SSR) is a rendering method where HTML is generated on the server before being sent to the browser.

Unlike CSR, users receive fully rendered HTML immediately, improving SEO and initial loading speed.

Frameworks like Next.js are widely used for SSR in React applications.

Definition of SSR

In SSR, the server processes React components and generates complete HTML before sending it to the client.

The browser receives ready-to-display content instead of building everything using JavaScript.

How SSR Works in React

Here’s the SSR workflow:

1. User requests a webpage
2. Server runs React components
3. HTML is generated on the server
4. Fully rendered HTML is sent to browser
5. Browser displays content immediately
6. React hydrates the page for interactivity

Hydration connects server-rendered HTML with React event handlers on the client side.

SSR with Next.js

Next.js makes SSR implementation easier using functions like:

export async function getServerSideProps() {
  const data = await fetchData();

  return {
    props: { data },
  };
}

This function runs on every request and generates fresh HTML dynamically.

Request-Response Lifecycle

User Request
      ↓
Server Runs React Components
      ↓
HTML Generated on Server
      ↓
Browser Receives Ready HTML
      ↓
Content Appears Immediately
      ↓
React Hydration Starts

HTML Generated on Server

Example of server-rendered HTML:

<h1>SSR Page in React</h1>
<p>Content generated on the server.</p>

This HTML is immediately visible to users and search engines.

Pros of SSR

• Better SEO
  Search engines can easily crawl server-rendered HTML content.
• Faster Initial Page Load
  Users see meaningful content quickly without waiting for JavaScript execution.
• Improved Social Sharing Previews
  Social media platforms can correctly read metadata and previews from SSR pages.

Cons of SSR

• Higher Server Cost
  Servers must render pages for every request, increasing infrastructure usage.
• Slower Navigation After First Load
  Subsequent page transitions may feel slower compared to CSR apps.
• More Complex Infrastructure
  SSR applications require backend rendering logic, caching strategies, and deployment optimization.

Best Use Cases for SSR

• E-commerce Websites
  Product pages benefit greatly from SEO and fast initial loading.
• Blogs
  Search visibility is critical for content-based websites.
• Marketing Websites
  Landing pages need strong SEO and social media previews.

What Is Pre-rendering in React JS?

Pre-rendering is a technique where HTML pages are generated before users request them, usually during build time. This approach is also called Static Site Generation (SSG).

Definition of Pre-rendering

In pre-rendering, React pages are converted into static HTML files during the build process instead of generating them dynamically per request. These static files are then served instantly to users.

Static Site Generation (SSG)

SSG creates pages ahead of time and stores them as static assets. Popular React frameworks like Next.js support SSG.

Build-Time HTML Generation

During deployment:

1. React pages are generated
2. HTML files are created
3. Static assets are deployed to CDN
4. Users receive prebuilt pages instantly

How Pre-rendering Differs from SSR

Feature	Pre-rendering (SSG)	SSR
HTML Generation	Build Time	Request Time
Speed	Extremely Fast	Fast
Server Usage	Very Low	Higher
Dynamic Content	Limited	Excellent
Hosting Cost	Lower	Higher

Next.js Static Generation Example

export async function getStaticProps() {
  const posts = await fetchPosts();

  return {
    props: { posts },
  };
}

The page is generated once during build time.

Pros of Pre-rendering

• Extremely Fast Loading
  Static files are served directly from CDN networks with minimal delay.
• Excellent SEO
  Search engines receive fully rendered HTML immediately.
• Lower Hosting Costs
  Static hosting requires fewer server resources compared to SSR.

Cons of Pre-rendering

• Rebuild Required for Updates
  Content changes often require rebuilding and redeploying the site.
• Not Suitable for Real-Time Apps
  Applications needing live data updates may not work efficiently with static generation.

Best Use Cases for Pre-rendering

• Documentation Sites
  Technical documentation benefits from static delivery speed.
• Portfolio Websites
  Personal websites usually contain mostly static content.
• Landing Pages
  Marketing pages load extremely fast with pre-rendering.

Understanding Real-Life Uses of SSR vs CSR vs Pre-rendering in React JS

1. Google using SSR for Faster Initial Load:
   Google uses Server-Side Rendering (SSR) to serve content quickly to users. This approach helps in reducing the initial load time by allowing the server to generate the HTML content before sending it to the user’s browser.
   

   
       export async function getServerSideProps() {  
         const res = await fetch('https://api.example.com/data');  
         const data = await res.json();  
         return { props: { data } };  
       }  
       

   The output of implementing SSR is a noticeably faster initial page-rendering time, enhancing user experience and SEO.
2. Facebook using CSR for Interactive UIs:
   Facebook utilises Client-Side Rendering (CSR) to manage interactive user interfaces. With components rendering on the client side, it allows dynamic interaction without reloading the page.
   

   
       function App() {  
         const [data, setData] = useState([]);  
         useEffect(() => {  
           fetch('https://api.example.com/data')  
           .then(response => response.json())  
           .then(data => setData(data));  
         }, []);  
         return (
   {data.map(item => (
   {item.name}
   ))}
   );  
       }  
       

   CSR offers a seamless user experience with fluid transitions and quick responses to user actions.
   
3. Airbnb using Pre-rendering for Static Pages:
   Airbnb implements Pre-rendering to serve static pages efficiently. This is perfect for content that doesn’t change frequently, ensuring quick load times without server load.
   

   
       export async function getStaticProps() {  
         const res = await fetch('https://api.example.com/data');  
         const data = await res.json();  
         return { props: { data } };  
       }  
       

   Pre-rendering leads to excellent performance for static content, providing users with instant access to information.
   

SSR vs CSR vs Pre-rendering in React JS- Interview Questions Overview

1. What are the scenarios where SSR (Server-Side Rendering) is preferred over CSR (Client-Side Rendering)?
   SSR is great when you need quick load times and SEO advantages. It’s perfect if your project prioritises catching search engine bots or when your users have slower internet connections.
2. How does pre-rendering improve performance in React applications?
   Pre-rendering creates a static HTML file during the build time, improving load speed significantly. It’s like having pre-cooked meals—you just gotta warm ’em up.
3. Is it possible to switch between CSR and SSR depending on user actions?
   Absolutely! You can initially render with SSR and switch to CSR for specific interactive components. It’s like opening a door, locking it, then making it automatic.
4. What are the common pitfalls when implementing SSR in React?
   Common issues involve poor caching, large bundle sizes, and dealing with third-party libraries that rely on window or document objects. Always double-check your configuration.
   
5. Can pre-rendering be used in conjunction with a REST API?
   Sure thing! Pre-rendering can be integrated with REST APIs, but remember to handle API data wisely to avoid stale content.
6. How does SSR handle large-scale applications?
   In large-scale apps, SSR maintains speed by offering cache strategies and optimising asset delivery. Still, scaling requires powerful server resources.
   
7. Why might CSR not be the best choice for e-commerce websites?
   CSR might fall short for e-commerce due to slower first-time loading and lesser SEO benefits. You don’t want your products hiding from customers, right?
   
8. Can you leverage SSR and CSR together in hybrid apps?
   Yes, developers can use a configuration setup to mix both SSR and CSR, benefiting from both methods and crafting a hybrid solution.

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Conclusion

Completing ‘SSR vs CSR vs Pre-rendering in React JS’ equips you with the knowledge to choose the best rendering strategy for your projects, enhancing performance and user experience. Why not try it yourself? Discover more programming tips on Newtum and boost your coding skills in Java, Python, and beyond.

Edited and Compiled by

This article was compiled and edited by @rasikadeshpande, who has over 4 years of experience in writing. She’s passionate about helping beginners understand technical topics in a more interactive way.

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