Understanding Server-Side Rendering (SSR) and Static Site Generation (SSG)

Server-Side Rendering (SSR) 🍕

Server-Side Rendering (SSR) is a powerful technique in Next.js where web pages are rendered on the server for each user request, rather than in the client's browser. This means when a user navigates to a page, the server fetches any necessary data and generates the complete HTML content before sending it to the client. The browser receives a fully formed HTML page, ready to be displayed immediately.

How SSR Works in Next.js

In Next.js, you implement SSR by exporting an asynchronous function called getServerSideProps from your page file. This function runs on the server with every incoming request, allowing you to fetch dynamic or real-time data and pass it as props to your React component.

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

export default function DynamicPage({ data }) {
  return (
    <div>
      <h1>{data.title}</h1>
      <p>{data.content}</p>
    </div>
  );
}
            
        

Benefits of SSR 🚀

• Improved Performance: By delivering pre-rendered HTML, SSR significantly reduces the initial load time and Time to First Byte (TTFB), offering an immediate visual response to users.
• Enhanced SEO: Search engines can easily crawl and index the fully rendered content, which positively impacts your application's search engine ranking.
• Better User Experience: Users, especially those on slower networks or less powerful devices, benefit from faster initial loads as the browser has less JavaScript to download and execute initially.
• Dynamic Content: SSR is ideal for websites with dynamic or personalized content that changes frequently, such as e-commerce sites, social media feeds, or real-time chat applications.

When to Use SSR

Choose SSR when your application requires:

• Content that updates frequently and needs to be current with every request.
• Personalized content based on user data or real-time information.
• An interactive user experience where real-time data is crucial.

Static Site Generation (SSG) ⚡

Static Site Generation (SSG) is a method where HTML pages are pre-rendered at build time. This means all the pages are generated into static HTML files during the project's build process, before any user even visits the site. When a user requests a page, the server simply sends these ready-made HTML files.

How SSG Works in Next.js

Next.js supports SSG through functions like getStaticProps and getStaticPaths.

The getStaticProps function runs at build time and allows you to fetch external data (e.g., from a headless CMS or API) to pass as props to your page component.

            
// For a static page with data
export async function getStaticProps() {
  const res = await fetch('https://api.example.com/posts');
  const posts = await res.json();
  return {
    props: { posts },
  };
}

export default function BlogList({ posts }) {
  return (
    <ul>
      {posts.map(post => <li key={post.id}>{post.title}</li>)}
    </ul>
  );
}
            
        

For dynamic routes (e.g., individual blog posts), getStaticPaths is used to define a list of paths that should be pre-rendered at build time.

            
// For dynamic static pages (e.g., /posts/[id])
export async function getStaticPaths() {
  // Fetch all possible post IDs
  const res = await fetch('https://api.example.com/posts');
  const posts = await res.json();
  const paths = posts.map(post => ({ params: { id: post.id.toString() } }));

  return { paths, fallback: false }; // fallback: false means pages not returned by getStaticPaths will 404.
}

export async function getStaticProps({ params }) {
  const res = await fetch(`https://api.example.com/posts/${params.id}`);
  const post = await res.json();
  return { props: { post } };
}

export default function Post({ post }) {
  return (
    <div>
      <h1>{post.title}</h1>
      <p>{post.body}</p>
    </div>
  );
}
            
        

Benefits of SSG 🏆

• Blazing Speed: Pages load incredibly fast because they are pre-built HTML files, served directly.
• Enhanced Scalability: Static files can be easily served by Content Delivery Networks (CDNs) globally, handling massive traffic efficiently with minimal server resources.
• Improved Security: With content pre-generated, there's less reliance on dynamic server logic, reducing potential attack vectors.
• Superior SEO: Search engines favor fast, static sites, which leads to better indexing and higher rankings.
• Cost-Efficiency: Hosting static files is generally more affordable than maintaining dynamic server-side resources, leading to lower hosting costs.

When to Use SSG

Opt for SSG when your application features:

• Content that does not change frequently, such as blogs, documentation, portfolios, or marketing sites.
• High-traffic websites where speed and scalability are paramount.
• A need for excellent SEO performance and low hosting costs.

SSR vs. SSG: Choosing the Right Approach 🤔

While both SSR and SSG offer significant advantages over traditional client-side rendering, especially for performance and SEO, they cater to different needs. The core difference lies in when the HTML is generated.

• Rendering Time: SSG renders pages at build time, while SSR renders pages on the server at request time.
• Content Freshness: SSR always displays the latest data because it generates the page for each request. SSG, on the other hand, serves pre-built content, meaning updates require a re-build (unless using Incremental Static Regeneration, ISR).
• Performance: SSG generally offers faster initial page loads due to content being served from CDNs. SSR can be slower for individual requests as the server has to process and render the page each time.
• Server Load & Costs: SSG reduces server load and operational costs by serving static files. SSR increases server load as it dynamically generates pages per request.
• Interactivity: SSR websites provide a more interactive user experience for dynamic content. SSG websites are largely static unless combined with client-side rendering.

The choice between SSR and SSG depends on your project's specific requirements, particularly how frequently your content changes and your need for real-time data versus maximum performance and scalability. Next.js offers the flexibility to use both methods within the same application, allowing you to choose the best rendering strategy for each page.