The Value of Next.js SSR | Sara Keyser Light

As modern web applications become increasingly dynamic, performance and user experience have become central to their success. Server-side rendering (SSR) is one of the key tools that developers have to improve these aspects, and Next.js, one of the most popular React frameworks, has built-in support for SSR.

In this post, I'll break down the value of SSR in Next.js, when it’s appropriate to use, and provide concrete code examples to help you understand how to use SSR effectively in production applications.

The Case for SSR in Next.js

1. Faster Time-to-Content

When it comes to user experience, time-to-content is one of the most important metrics. SSR allows you to pre-render a page on the server, meaning the browser can load HTML directly, reducing the time it takes to show meaningful content to the user.

For instance, Google’s Core Web Vitals places a premium on metrics like Largest Contentful Paint (LCP) and Time to First Byte (TTFB). These metrics heavily benefit from SSR, as the server provides a fully rendered page, rather than waiting for client-side JavaScript to download, parse, and execute before rendering content.

2. SEO Benefits

Search engines like Google still rely heavily on HTML to index content. If you're building a website where SEO is important (e.g., blogs, landing pages, e-commerce), SSR can improve how your pages are indexed by search engines. A server-rendered page is much easier for Googlebot to crawl and understand.

While static site generation (SSG) is often more performant, SSR ensures that the content is always fresh. For example, an e-commerce website where inventory updates in real-time needs SSR to ensure that search engines are seeing the latest data.

3. Personalization & Authentication

A lot of modern applications need to render different content for different users (e.g., personalized dashboards, user-specific recommendations). Server-side rendering allows you to conditionally render content based on the user’s authentication status or user data stored on the server, without relying on JavaScript to load and hydrate the page on the client.

For instance, consider a dashboard where logged-in users see their personal data, while unauthenticated users see a login prompt. SSR lets you handle this efficiently and securely.

When Should You Use SSR in Next.js?

Next.js gives you the flexibility to choose between SSR, static site generation (SSG), and client-side rendering (CSR). The decision depends on your use case. Here are some scenarios where SSR shines:

1. Dynamic Content

If your website needs to display dynamic, user-specific, or frequently updated data, SSR is a good fit. For example:

User dashboards: Content that’s personalized based on user identity (e.g., account settings, recent activity, etc.)
Real-time data: Applications that need to display live data, like stock tickers, sports scores, or inventory levels.

2. SEO Needs

If search engine optimization is a priority and you need pages to be indexed properly and quickly, SSR is beneficial. Static generation (SSG) can be used if content does not change often, but if content is highly dynamic or user-dependent, SSR will provide the most up-to-date results for crawlers.

3. Complex Pages

Pages that need complex data manipulation or have slow-loading APIs can benefit from SSR, because it allows the server to make all those calculations and data fetches before sending the page to the client.

4. First-Visit Performance

If you're focusing on the initial page load experience, SSR ensures that users see the page content quickly. In contrast, CSR (client-side rendering) can result in a slower first-page load because JavaScript needs to download, parse, and render the page client-side.

Next.js SSR Implementation: Code Examples

Let’s dive into some basic examples to see how SSR works in practice.

Basic SSR with `getServerSideProps`

Next.js provides getServerSideProps to fetch data on the server and pass it as props to your page. This function is called on each request, meaning the page will always be pre-rendered with fresh data.

Here's an example of how to implement SSR with Next.js using getServerSideProps.

Example 1: Server-Side Rendering a Blog Post

jsx

// pages/blog/[id].js

import React from "react";

const BlogPost = ({ post }) => {
  return (
    <div>
      <h1>{post.title}</h1>
      <p>{post.content}</p>
    </div>
  );
};

export async function getServerSideProps(context) {
  const { id } = context.params;

  // Fetch the blog post from an API or database
  const res = await fetch(`https://api.example.com/blog/${id}`);
  const post = await res.json();

  return {
    props: { post }, // will be passed to the page component as props
  };
}

export default BlogPost;

In the example above, getServerSideProps is used to fetch a blog post on the server for each request. This is useful if the blog post data is updated frequently, ensuring that users always see the most up-to-date content.

Using SSR for Authentication

Sometimes you need to display different content based on whether a user is logged in. Here's an example of using SSR to check authentication status.

Example 2: Server-Side Rendering a Protected Page

jsx

// pages/dashboard.js

import React from "react";

const Dashboard = ({ user }) => {
  if (!user) {
    return <p>You must be logged in to view this page.</p>;
  }

  return (
    <div>
      <h1>Welcome, {user.name}!</h1>
      <p>Your account balance: ${user.balance}</p>
    </div>
  );
};

export async function getServerSideProps(context) {
  const token = context.req.cookies.token; // Get token from cookies

  if (!token) {
    return { props: { user: null } }; // Not logged in
  }

  // Fetch user data from an API
  const res = await fetch("https://api.example.com/user", {
    headers: { Authorization: `Bearer ${token}` },
  });
  const user = await res.json();

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

export default Dashboard;

In this example, we check if the user is authenticated by inspecting the cookies sent with the request. If the user is authenticated, we fetch user data from an API and pass it as props to the page.

When NOT to Use SSR

While SSR has its advantages, there are also scenarios where it's not the best choice:

1. When Data Does Not Change Frequently

If your content doesn’t change much (e.g., static blog content or marketing pages), using Static Site Generation (SSG) or even a hybrid approach with Incremental Static Regeneration (ISR) is often more efficient.

2. Performance Concerns

SSR comes with some overhead because the server must render the page on every request. If your pages are highly dynamic, this can result in slower server response times. In such cases, SSR can be complemented with caching strategies or replaced with static rendering methods like SSG or CSR.

3. High Traffic Websites

For sites that experience high traffic, SSR can put a heavy load on your server, as each request requires a fresh rendering. Implementing caching mechanisms or leaning towards static generation might be more scalable.

Conclusion

Next.js SSR offers a powerful tool for building dynamic, SEO-friendly applications. By rendering pages on the server, you can deliver content quickly to users and ensure that search engines index your pages properly. However, it's important to evaluate your use case carefully — SSR is not always the best solution, and Next.js provides a range of tools like SSG and ISR to meet different needs.

If you’re building a modern web app that requires dynamic content, fast first-page loads, and SEO-friendly features, SSR with Next.js is an invaluable approach for production-grade applications.

The Value of Next.js SSR: When to Use It and Code Examples for Production