Dynamic Rendering in Next.js: Implementing Server-Side Rendering and Incremental Static Regeneration

If you are building a web application with Next.js, you might be wondering how to optimize your site for performance and SEO. One of the key features of Next.js is its ability to render pages on the server or on the client, depending on the situation. This is called dynamic rendering, and it can help you deliver fast and user-friendly experiences to your visitors.

In this blog post, I will explain what dynamic rendering is, how it works in Next.js, and how to implement two common rendering techniques: server-side rendering (SSR) and incremental static regeneration (ISR).

What is dynamic rendering?

Dynamic rendering means that the HTML content of a page is generated at different times, depending on the request. For example, some pages might be rendered on the server when they are first requested, while others might be rendered on the client when they are navigated to. This allows you to tailor the rendering process to the needs of each page and optimize for performance and SEO.

Next.js supports three main types of dynamic rendering:

• Static generation: The HTML content of a page is generated at build time and served from a CDN(Content Delivery Network). This is the fastest and most SEO-friendly option, but it requires that the data for the page is available at build time and does not change frequently.
• Server-side rendering: The HTML content of a page is generated on the fly by the server when a request comes in. This is useful for pages that need to display dynamic or personalized data that cannot be pre-rendered at build time.
• Client-side rendering: The HTML content of a page is generated by the browser when the user navigates to it. This is useful for pages that do not need SEO or initial loading performance, but rely on interactivity and user input.

How does dynamic rendering work in Next.js?

Next.js provides a simple and flexible way to implement dynamic rendering for your pages. You can choose which rendering strategy to use for each page by exporting one of these functions from your page component:

• getStaticProps: This function tells Next.js to pre-render the page at build time using static generation. You can use this function to fetch any data that is needed for the page and pass it as props to the component. Next.js will then generate a static HTML file for the page and serve it from a CDN.
• getServerSideProps: This function tells Next.js to render the page on the server when a request comes in using server-side rendering. You can use this function to fetch any data that is needed for the page and pass it as props to the component. Next.js will then generate an HTML response for the page and send it to the browser.
• getStaticPaths: This function tells Next.js which paths to pre-render at build time using static generation. You can use this function to specify a list of dynamic routes that have different data based on the URL parameters. Next.js will then generate a static HTML file for each path and serve them from a CDN.

You can also combine these functions to create hybrid rendering strategies, such as incremental static regeneration (ISR). ISR allows you to update the static HTML files of your pages at runtime without rebuilding your entire site. You can use this feature to keep your pages fresh with new data while still benefiting from fast loading times and SEO.

How to implement SSR and ISR in Next.js?

Let’s see how to implement SSR and ISR in Next.js, two powerful data-fetching methods that can improve your website’s performance and user experience.

SSR stands for Server-Side Rendering, which means that the page is rendered on the server and sent to the browser as HTML. This way, the page loads faster and is SEO-friendly, since search engines can crawl the content easily. SSR is useful for pages that need to display dynamic data that changes frequently, such as a product page or a blog post.

ISR stands for Incremental Static Regeneration, which means that the page is pre-rendered at build time and served as a static file. However, unlike regular static generation, ISR allows you to update the page in the background as new data becomes available, without rebuilding the entire site. ISR is useful for pages that display data that changes occasionally, such as a dashboard or a news feed.

To use SSR in Next.js, you need to export a function called getServerSideProps from your page component. This function runs on the server every time a request is made to that page, and it can fetch data from any source, such as an API or a database. The data returned by this function is passed as props to your page component, which can then render it on the server.

Here’s an example of how to use SSR in Next.js:

import { getServerSideProps } from 'next'

function Home({ posts }) {
  // Render posts on the server
  return (
    <div>
      <h1>Latest Posts</h1>
      <ul>
        {posts.map((post) => (
          <li key={post.id}>
            <h2>{post.title}</h2>
            <p>{post.content}</p>
          </li>
        ))}
      </ul>
    </div>
  )
}

// Fetch posts from an API on the server
export async function getServerSideProps() {
  const res = await fetch('https://example.com/api/posts')
  const posts = await res.json()

  return {
    props: {
      posts,
    },
  }
}

export default Home

To use ISR in Next.js, you need to export a function called getStaticProps from your page component. This function runs at build time on the server and can fetch data from any source, just like getServerSideProps. The difference is that you also need to specify a revalidate property, which tells Next.js how often (in seconds) to regenerate the page in the background when new data is available.

Here’s an example of how to use ISR in Next.js:

import { getStaticProps } from 'next'

function Home({ posts }) {
  // Render posts statically
  return (
    <div>
      <h1>Latest Posts</h1>
      <ul>
        {posts.map((post) => (
          <li key={post.id}>
            <h2>{post.title}</h2>
            <p>{post.content}</p>
          </li>
        ))}
      </ul>
    </div>
  )
}

// Fetch posts from an API at build time
export async function getStaticProps() {
  const res = await fetch('https://example.com/api/posts')
  const posts = await res.json()

  return {
    props: {
      posts,
    },
    // Regenerate the page every 10 seconds
    revalidate: 10,
  }
}

export default Home

As you can see, SSR and ISR are very similar in terms of how they fetch data and pass it to your page component. The main difference is when and how often they render the page. SSR renders the page on every request, while ISR renders the page once and updates it periodically.

Both methods have their pros and cons, depending on your use case and requirements. SSR can provide faster initial loading and better SEO, but it can also increase server load and latency. ISR can provide faster subsequent loading and better user experience, but it can also cause stale data and lower SEO.

To choose the right approach for your frontend development needs, you need to consider factors such as:

• How frequently does your data change?
• How important is SEO for your website?
• How much traffic do you expect on your website?
• How complex is your data-fetching logic?

That’s it! You now know what SSR and ISR are and how to use them in Next.js. I hope you found this blog post helpful and informative. If you have any questions or feedback, feel free to leave a comment below or reach out to me on Twitter/LinkedIn. Thanks for reading and happy coding!

If you want to learn more about Next.js and Dynamic Rendering check out my previous article about Static Site Generation with Next.js and watch this amazing video from the Vercel team about Server-side data fetching in Next.js 12 and Next.js 13.