Server-Side Rendering (SSR) in Next.js is a technique where pages are rendered on the server at request time, allowing for dynamic content that can be generated based on incoming requests. This approach contrasts with Static Generation (SSG), where pages are pre-rendered at build time. SSR is particularly useful for applications that require real-time data or personalization, as it allows the server to fetch and serve fresh content on each request.

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

In SSR, every time a user requests a page, the server generates the HTML for that page in real-time and sends it to the client. This process ensures that the user receives the latest data every time they visit the page. SSR is beneficial for pages that need to display frequently changing data or require authentication and user-specific information.

2. When to Use Server-Side Rendering

• Dynamic Data: Use SSR for pages that display frequently changing data, such as user profiles, dashboards, or real-time feeds.

• User-Specific Content: When content varies based on the user (e.g., authenticated user data), SSR is suitable.

• SEO Optimization: SSR provides fully rendered HTML to search engines, making it effective for SEO.

3. How to Implement Server-Side Rendering in Next.js

To implement SSR in Next.js, you can export an async function called getServerSideProps from your page component. This function runs on the server for every request and fetches data before rendering the page.

a. Basic Example of Server-Side Rendering

// pages/user/[id].js
export default function UserProfile({ user }) {
  return (
    <div>
      <h1>{user.name}</h1>
      <p>Email: {user.email}</p>
    </div>
  );
}

// This function is called on each request
export async function getServerSideProps({ params }) {
  const res = await fetch(`https://api.example.com/users/${params.id}`);
  const user = await res.json();

  // If the user is not found, you can return a 404 status
  if (!user) {
    return {
      notFound: true,
    };
  }

  return {
    props: {
      user, // Passed to the page component as props
    },
  };
}

4. Breaking Down the Example

• getServerSideProps: This function fetches data on each request. In the example above, it retrieves user information based on the user ID passed in the URL.

• Dynamic Content: Each time a request is made to /user/[id], the server fetches the latest user data and renders the page accordingly.

• Error Handling: If the user is not found, you can return a notFound key to display a 404 error page.

5. Benefits of Server-Side Rendering

• Fresh Data: SSR provides the latest data with every request, ensuring that users always see the most current information.

• SEO Optimization: SSR delivers fully rendered HTML to search engines, improving crawlability and indexing for SEO.

• Personalization: SSR allows for user-specific content to be generated dynamically based on the request.

6. Limitations of Server-Side Rendering

• Performance: Since pages are rendered on each request, SSR can introduce latency, especially for heavy data-fetching tasks.

• Increased Server Load: SSR requires the server to process each request, which can lead to higher server resource usage compared to static pages.

• Caching Strategies: While SSR provides fresh data, implementing caching strategies can be complex and is crucial for optimizing performance.

7. Using Middleware with SSR

You can also combine SSR with middleware in Next.js to handle authentication, redirects, and other logic before rendering the page. This allows you to control access to certain pages based on user authentication status or other criteria.

Summary

Server-Side Rendering (SSR) in Next.js is a powerful technique for delivering dynamic content by rendering pages on the server at request time. Key points about SSR include:

1. Dynamic Data: SSR fetches and renders data in real-time, ensuring users always see the latest information.

2. User-Specific Content: SSR is effective for generating personalized content based on user requests.

3. SEO Benefits: Fully rendered HTML improves SEO by making content accessible to search engines.

4. Performance Considerations: While SSR provides fresh data, it can introduce latency and increase server load, requiring careful optimization.

By leveraging SSR, you can build Next.js applications that are responsive to user needs, provide personalized experiences, and maintain strong SEO performance.