Server-Side Rendering (Next.js)

Server-Side Rendering (SSR) is a technique where the HTML is generated on the server for each request and then sent to the browser. This is in contrast to client-side rendering (CSR), where the browser renders the HTML after receiving a JavaScript bundle. Next.js is a popular React framework that simplifies server-side rendering, static site generation, and hybrid rendering for React applications.

In this guide, we’ll explore how Next.js handles Server-Side Rendering and why it is beneficial for React applications.

1. What is Server-Side Rendering (SSR)?

In SSR, the server generates the HTML for a web page before sending it to the client. This approach has several benefits:

Faster initial load: Since the server sends fully rendered HTML, the browser doesn’t need to process and render JavaScript before displaying content.
Better SEO: Search engine bots can crawl the fully rendered HTML easily, improving indexing and SEO.
Improved Performance: SSR helps with performance on slower networks, as the browser gets a fully rendered page immediately.

2. How SSR Works in Next.js

Next.js simplifies the process of server-side rendering by allowing pages to render dynamically on the server for each request.

When using SSR in Next.js, the framework uses the following approach:

The user requests a page.
The server processes the request, fetches data, and renders the page HTML on the server.
The HTML is sent to the client, which can immediately display the content.
The client-side React app then takes over and becomes interactive after the initial render.

3. Setting Up Server-Side Rendering in Next.js

Next.js allows you to create SSR pages using the getServerSideProps function. This function is run on the server for each request, ensuring that the content is always up to date.

3.1 Creating an SSR Page

Here’s how to use getServerSideProps in a Next.js page to fetch data on the server and render it on the page.

// pages/index.js
import React from 'react';

const Home = ({ data }) => {
  return (
    <div>
      <h1>Server-Side Rendered Page</h1>
      <p>{data}</p>
    </div>
  );
};

// getServerSideProps function runs on the server side to fetch data
export async function getServerSideProps() {
  // Simulating an API call or data fetch
  const response = await fetch('https://api.example.com/data');
  const data = await response.json();

  // Returning data as props to the component
  return {
    props: {
      data: data.message,  // Pass the fetched data as a prop
    },
  };
}

export default Home;

getServerSideProps: This is an async function that runs on the server side before the page is rendered. It can be used to fetch data, call APIs, or do other server-side tasks.
The data fetched in getServerSideProps is passed as a prop to the component and rendered on the page.

3.2 What Happens During SSR?

Page Request: When a user visits the page, Next.js calls getServerSideProps on the server.
Data Fetching: The server fetches data from an API, database, or any other data source.
Page Rendering: The page is rendered on the server with the fetched data.
Sending HTML to Browser: The fully rendered HTML is sent to the browser, which displays it immediately.
Client-Side React Activation: After the page is loaded, React takes over on the client side, and the app becomes interactive.

4. Key Advantages of SSR in Next.js

4.1 SEO Benefits

SSR ensures that the page content is fully rendered on the server, which makes it easier for search engines to crawl and index the content. This can improve your website’s SEO ranking.

Better SEO: Since the server sends fully rendered HTML, search engines like Google can easily crawl the page content.
Meta Tags: You can dynamically set meta tags for each page (e.g., for social sharing) directly in getServerSideProps.

4.2 Faster Initial Page Load

SSR improves the time-to-content (TTC) since the server sends the rendered HTML to the client. This is especially helpful for users with slow internet connections, as they get the content faster without waiting for JavaScript to load and render.

4.3 Dynamic Content

SSR is perfect for applications that need to render dynamic content for each request, such as:

User-specific data (e.g., profile information).
Real-time data updates (e.g., stock prices or weather reports).
Content based on user authentication.

5. Handling Errors and Fallbacks in SSR

Next.js also allows you to handle errors and implement fallback strategies. For example, you can handle errors in getServerSideProps by wrapping it in a try-catch block.

export async function getServerSideProps() {
  try {
    const response = await fetch('https://api.example.com/data');
    if (!response.ok) {
      throw new Error('Failed to fetch data');
    }
    const data = await response.json();

    return {
      props: { data: data.message },
    };
  } catch (error) {
    console.error(error);
    return {
      notFound: true,  // Automatically show the 404 page
    };
  }
}

Error Handling: If there’s an error during data fetching, you can return notFound: true to show the built-in 404 page or handle it as per your requirements.
Fallbacks: You can return fallback data to ensure that the page still renders even when data fetching fails.

6. When to Use SSR in Next.js

SSR is useful in several scenarios:

SEO Optimization: If SEO is crucial for your application (e.g., blogs, e-commerce, marketing pages), SSR ensures search engines can index your content properly.
Dynamic Data: For pages that need real-time or frequently changing data (e.g., news, sports scores, stock prices), SSR ensures that users always see the latest content.
Personalized Content: For user-specific content (e.g., user dashboards, profile pages), SSR provides the data to the page on the server before it’s sent to the client.

However, SSR may not be necessary for every page. Static Site Generation (SSG) or Client-Side Rendering (CSR) might be better choices for pages that don’t require dynamic data or frequent updates.

7. Comparing SSR, SSG, and CSR in Next.js

SSR (Server-Side Rendering): HTML is generated on the server for every request.
- Best for: SEO, personalized or dynamic content, and pages with frequently changing data.
SSG (Static Site Generation): HTML is generated at build time, not on each request.
- Best for: Static content that doesn’t change often (e.g., blog posts, documentation).
CSR (Client-Side Rendering): HTML is generated in the browser using JavaScript, and the initial page load is typically slower.
- Best for: Single-page applications (SPAs), where SEO isn’t a primary concern.

Next.js gives you the flexibility to choose between SSR, SSG, and CSR for different pages, depending on your application’s needs.