The Ultimate Guide to Next.js Server Side Rendering to Level up Your App

Next.js, a powerful framework built on React, is known for its ability to optimize web applications through various rendering strategies, including Server-Side Rendering (SSR), Static Site Generation (SSG), and Client-Side Rendering (CSR).

This blog delves into the intricacies of SSR in Next.js, explaining its benefits, how it compares to other rendering methods, and practical implementation tips.

What is Next.js Server-Side Rendering?

Server-side rendering (SSR) in Next.js involves generating the HTML for each page on the server for every request. This approach contrasts with Client-Side Rendering (CSR), where the browser generates JavaScript HTML. SSR can significantly enhance performance and SEO by reducing the time it takes for the page to become interactive.

How SSR Works

When a user requests a page, the Next.js server fetches the necessary data, renders the page HTML on the server, and sends this HTML to the client. This process ensures that the user sees a fully rendered page almost immediately, even before the JavaScript bundles have loaded.

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// pages/index.js
export async function getServerSideProps() {
  // Fetch data from an API
  const res = await fetch('https://api.example.com/data');
  const data = await res.json();

  // Pass data to the page via props
  return { props: { data } };
}

function HomePage({ data }) {
  return (
    <div>
      <h1>Data from API</h1>
      <pre>{JSON.stringify(data, null, 2)}</pre>
    </div>
  );
}

export default HomePage;

Benefits of Server-Side Rendering

• Improved Performance: By rendering the page HTML on the server, SSR reduces the initial load time, providing a faster Time to First Byte (TTFB) and an immediate visual response, enhancing the user experience.

• SEO Advantages: Search engines can easily crawl and index the fully rendered HTML, improving the visibility of your web application in search results.

• Better User Experience: Users on slower networks or less powerful devices benefit from faster initial loads, as the browser has less client-side JavaScript to download, parse, and execute.

SSR vs. Static Site Generation (SSG)

While SSR generates HTML on each request, Static Site Generation (SSG) pre-renders pages at build time. This approach is beneficial for static content that doesn't change often.

Key Differences

• Build Time: SSG generates HTML during the build process, while SSR generates HTML on each request.

• Caching: SSG pages can be cached more effectively, reducing server load and enhancing performance.

• Flexibility: SSR is more flexible for dynamic content that changes frequently, while SSG is optimal for static content.

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// pages/index.js
export async function getStaticProps() {
  // Fetch data from an API
  const res = await fetch('https://api.example.com/data');
  const data = await res.json();

  // Pass data to the page via props
  return { props: { data } };
}

function HomePage({ data }) {
  return (
    <div>
      <h1>Data from API</h1>
      <pre>{JSON.stringify(data, null, 2)}</pre>
    </div>
  );
}

export default HomePage;

Implementing SSR with getServerSideProps

In Next.js, you can implement SSR using the getServerSideProps function. This function runs on the server and fetches data needed to render the page.

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

function HomePage({ data }) {
  return (
    <div>
      <h1>Data from API</h1>
      <pre>{JSON.stringify(data, null, 2)}</pre>
    </div>
  );
}

export default HomePage;

SSR with Server Components

Next.js also supports Server Components , which allow you to render parts of your UI on the server. This can improve performance by reducing the amount of JavaScript sent to the client.

Benefits of Server Components

• Data Fetching: Moves data fetching to the server, closer to your data source.

• Security: Keeps sensitive data and logic on the server.

• Caching: Renders can be cached and reused across requests and users.

• Performance: Reduces client-side JavaScript needed, benefiting users with slower internet or devices.

Client-Side Rendering in Next.js

Client-Side Rendering (CSR) is another rendering method where JavaScript runs in the browser to generate HTML. While CSR can provide rich interactivity, it often results in slower initial load times compared to SSR and SSG.

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import { useEffect, useState } from 'react';

function HomePage() {
  const [data, setData] = useState(null);

  useEffect(() => {
    async function fetchData() {
      const res = await fetch('https://api.example.com/data');
      const data = await res.json();
      setData(data);
    }
    fetchData();
  }, []);

  if (!data) {
    return <div>Loading...</div>;
  }

  return (
    <div>
      <h1>Data from API</h1>
      <pre>{JSON.stringify(data, null, 2)}</pre>
    </div>
  );
}

export default HomePage;

Static Site Generation in Next.js

Static Site Generation (SSG) pre-renders pages at build time, making it a great choice for static content that doesn't change frequently. This method can significantly improve performance by serving cached HTML.

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

function HomePage({ data }) {
  return (
    <div>
      <h1>Data from API</h1>
      <pre>{JSON.stringify(data, null, 2)}</pre>
    </div>
  );
}

export default HomePage;

Using Next.js Proxy for Data Fetching

Next.js provides built-in support for API routes, which can act as a proxy for external API requests. This setup can help manage API keys securely and reduce CORS issues.

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// pages/api/data.js
export default async function handler(req, res) {
  const apiRes = await fetch('https://api.example.com/data');
  const data = await apiRes.json();
  res.status(200).json(data);
}

Conclusion

Next.js offers a flexible approach to rendering with Server-Side Rendering (SSR), Static Site Generation (SSG), and Client-Side Rendering (CSR). Each method has its advantages and is suited to different types of web applications. You can optimize your Next.js application for performance, SEO, and user experience by understanding these rendering strategies and implementing them correctly.