Exploring Web Rendering Techniques in Next.js 15: A Deep Dive into SSG, SSR, CSR, and ISR

In the React ecosystem, Next.js has long been a dominant force, providing developers with an adaptable framework for creating scalable, high-performing web apps. The App Router keeps developing with Next.js 15, which offers improved tools for controlling page rendering. Understanding Next.js rendering techniques—Static Site Generation (SSG), Server-Side Rendering (SSR), Incremental Static Regeneration (ISR) , and Client-Side Rendering (CSR)—is essential to maximising its potential, no matter whether you're creating a dynamic dashboard, a hybrid content platform, or a static marketing site.

In deep drive we will explore rendering stratgy. And understand how it works in next.js 15. provide practical examples, and discuss when we can use this in our real time project. Let's get started.

Why Rendering Matters ?

Rendering determines how and when our web pages are generated and delivered to users. It affects our web app performance (How fast our page load) to SEO (how well search engines index out web pages) to user experience (how users interact with applications). Nextjs 15,with its app router and enhanced Server Components, provides you with precise control over these compromises. However, incredible strength requires extensive knowledge, so let's examine the four fundamental strategies.

1. Static Site Generation (SSG)

Static Site Generation pre-renders pages at build time, generating static HTML files that can be served instantly to users. This approach is ideal for content-heavy pages that don’t require frequent updates, such as blogs, marketing sites, and documentation.

🚀 Key Features
✔️ Pre-rendered at Build Time: Pages are generated as static HTML files during the build process.

✔️ Reduced server load : Pages are pre-built and cached on a CDN.

✔️ SEO-friendly : Pre-generated pages allow search engines to index content easily.

✔️ Fast Load Times: Minimal latency since the page is pre-built and cached.

📌 When to Use SSG
✅ Blogs and News Websites: Articles and posts don’t change frequently.

✅ Marketing Websites: Pages like landing pages, product descriptions, or FAQs.

✅ E-commerce Product Listings: For products with infrequent updates.

Example :

// app/page.tsx
import Image from 'next/image';

export default function Home( ) {
  return (
    <main>
      <h1>Welcome to our Web Solution</h1>
      <Image src="/logo.jpg" alt="Our Team" width={200} height={400} />
      <p>We’re a team passionate about building great web experiences.</p>
    </main>
  );
}

2. Server-Side Rendering (SSR)

SSR generates dynamic material that changes regularly or requires personalised data because it creates HTML on the server for every request.

🚀Key Features
✔️ Dynamic Content: Fresh data is fetched per request, ensuring the latest content is always delivered.

✔️ Great for personalization: Ideal for user-specific content.

✔️ SEO Friendly: Like SSG, SSR provides fully rendered HTML for search engines.

✔️ Higher server load : Each request generates a new response, increasing backend workload.

📌 When to Use SSR
✅ E-commerce Product Pages: Prices and stock change frequently.

✅ Social Media Feeds: Platforms like Twitter or Instagram rely on SSR to serve up-to-date posts and comments tailored to the user.

✅ User Dashboards: User-specific data must always be fresh.

✅ Real-Time Analytics: Tools like Google Analytics dashboards use SSR to display live metrics that change constantly.

Example :

const getServerSideProps = async ( ) => { 
const response = await fetch(`http://localhost:3000/api/ product `, 
     { cache: "no-store" }); 
  return response.json();
}

export default function Home { 
const product = await fetchNews( );
 return ( 
    <main className="lg:px-20 md:px-10 px-5 py-10 text-blue-950">
     <h1>Server-Side Rendering</h1>
     <p>{product}</p>
    </main> 
);
}

3. Client-Side Rendering (CSR)

CSR produces pages entirely in the browser using JavaScript. This strategy is great for highly interactive applications where the initial load time is less crucial than dynamic updates.

🚀Key Features
✔️ Fast navigation within the app – Ideal for SPAs (Single Page Applications).

✔️ Highly Interactive: Ideal for applications with complex user interactions.

✔️ Data Fetching: Use useEffect or libraries like React Query to fetch data on the client side.

✔️ Not SEO-friendly by default: Content is rendered on the client, which may not be indexed well.

✔️ No Server Rendering: All rendering logic runs in the browser, reducing server workload.
**
📌 When to Use SSR**
✅ Single-Page Applications (SPAs): Applications like Gmail or Trello.

✅ Gaming Platforms: Interactive games or simulations.

✅ Chat Applications: Apps like Slack or Discord use CSR to update messages in real time, relying on WebSockets or API polling

✅ Admin Panels: Highly interactive dashboards with real-time updates.

Example :

'use client'
import { useEffect, useState } from "react";

export default function Page( ) { 

const [data, setData] = useState(null); 
useEffect(() => { 
fetch('https://api.example.com/data') 
.then((res) => res.json()) .then((data) => setData(data)); 
}, []);
 return (
   <main>
     <h1>Client-Side Rendering</h1> 
       <p>{data ? data : "Loading..."}</p>
   </main>
 );
}

4. Incremental Static Regeneration (ISR)

Static pages can be updated using ISR without needing to be completely rebuilt once they have been constructed. This is especially helpful for big websites whose material changes often.

🚀Key Features
✔️ Hybrid Approach: Combines SSG with dynamic updates.

✔️ Updates content without full redeployment – No need to rebuild the entire site.

✔️ Edge Optimization: Next.js 15 improves ISR with better cache handling at the edge.

✔️ Scalable: Ideal for large sites with frequently changing content.

✔️ SEO-friendly – Pages are pre-rendered and indexed by search engines.

📌 When to Use SSR
✅ News Websites (CNN, BBC) – Articles are updated frequently but don’t need instant updates.

✅ Job Boards: Job listings that are updated daily or weekly (e.g., Indeed).

✅ Sports Scoreboards: Scores and stats are updated at regular intervals.

✅ E-commerce with Frequent Updates: An online store like Amazon might use ISR for product pages that need hourly stock or price refreshes without rebuilding the entire site.

export async function getStaticProps( ) { 
   const data = await fetchData(); 
    return { props: { data }, 
      revalidate: 60, // Regenerate every 60 seconds 
    };
}
export default function Page ({ data }) {
 return ( 
   <main> 
              <h1> Incremental Static Regeneration</h1>
               <div>{data}</div>
    <main> 
);
} 

Conclusion

Launching a Blog: Use SSG for speed and simplicity. Rebuild when you publish new posts.Building a Social Network: Choose SSR to ensure fresh, personalized feeds with good SEO.Creating a Design Tool: Go with CSR for a highly interactive, client-driven experience.Running an Online Store: Opt for ISR to balance fast loads with periodic inventory updates

The advantage of Next.js 15 is that it allows you to combine these methods in a single application. For instance, a news website may employ ISR for articles, SSR for user comments, CSR for a live chat function, and SSG for its "About" page. Which rendering technique seems most appropriate for the type of project you are considering?

🙏 Thank You for Reading