Introduction to Incremental Static Generation (ISG) in Next.js

Next JS

In the world of web development, delivering high-performance and dynamic websites is crucial for providing an exceptional user experience. Static Generation (SG) has been a go-to approach for generating static pages in Next.js, ensuring fast load times and server efficiency. However, as applications become more dynamic, maintaining up-to-date content can be challenging. That's where Incremental Static Generation (ISG) steps in, bridging the gap between static pages and real-time updates.

Next.js, a popular React framework, introduces ISG as an advanced feature that takes the benefits of Static Generation and augments them with the ability to update pages at runtime. It offers developers the power to seamlessly blend pre-rendered pages with dynamic content, resulting in fast-loading websites that display the latest data.

Static Generation (SG) in Next.js

Static Generation is a feature in Next.js that allows you to pre-render pages at build time. This means that the HTML for each page is generated once and then served to clients as static files, greatly improving performance and reducing server load.

However, there are cases where Static Generation alone may not be sufficient. For example, if you have dynamic content that frequently changes or data that needs to be fetched from an external API, static pages generated during build time won't reflect the latest data.

Enter Incremental Static Generation (ISG)

Incremental Static Generation (ISG) is an advanced feature introduced in Next.js 10.2 that combines the benefits of Static Generation with the ability to update static pages at runtime. It allows you to re-generate static pages on-demand or in the background, ensuring that your website or application always displays up-to-date information.

How does ISG work?

ISG leverages Next.js's hybrid approach to rendering. It initially generates static pages during the build process but leaves certain parts of the page as "unfilled" or "unstable." These unfilled parts act as placeholders for dynamic content that will be generated or updated later.

When a user visits a page with unfilled parts, Next.js loads the static content immediately and then fetches the dynamic data in the background. Once the data is available, Next.js regenerates the page with the updated content and caches it for subsequent requests.

Benefits of ISG

Improved performance: ISG allows you to have the best of both worlds by serving static content for fast initial page loads while still updating and re-rendering dynamic parts as needed. This approach strikes a balance between performance and up-to-date information.
Real-time data: With ISG, you can fetch data from APIs or databases at runtime, ensuring that your pages are always displaying the latest information. This is particularly useful for frequently changing data, such as social media feeds or stock prices.
Lower server load: By generating and caching static pages, ISG reduces the load on your server. It can handle more traffic and decreases the need for frequent API calls or database queries for every page request.
Better user experience: ISG allows you to show meaningful content to users immediately, even if some parts are still loading. This reduces the time spent waiting for the page to load, leading to a better user experience and increased engagement.

Implementing ISG in Next.js

To illustrate how Incremental Static Generation works in Next.js, let's consider an example of a blog application.

Suppose you're building a blog application with Next.js, and you want to display a list of blog posts on the homepage. The blog posts are dynamic and can change frequently, so you want to ensure that the latest posts are always displayed.

To implement ISG in Next.js for this example:

Create a new Next.js project and set up the necessary files and folder structure.
In your pages directory, create a file called index.js. This will be the homepage of your blog application.
Inside index.js, define a functional component called HomePage that will render the blog post list.
Use the getStaticProps function to fetch the blog posts data during the build process. In this example, let's assume the blog posts are fetched from an API endpoint.

import React from 'react';

function HomePage({ posts }) {
  return (
    <div>
      <h1>Welcome to My Blog</h1>
      <ul>
        {posts.map((post) => (
          <li key={post.id}>{post.title}</li>
        ))}
      </ul>
    </div>
  );
}

export async function getStaticProps() {
  const res = await fetch('https://api.example.com/posts');
  const posts = await res.json();

  return {
    props: {
      posts,
    },
    revalidate: 60,
  };
}

export default HomePage;

In this example, we're using the getStaticProps function to fetch the blog posts data during the build process. The fetched data is passed as a prop (posts) to the HomePage component. Additionally, we set the revalidate option to 60 seconds, indicating that Next.js should attempt to re-generate the page and fetch updated data every 60 seconds.

Run the Next.js development server and navigate to the homepage. You should see the list of blog posts rendered.
If a new blog post is published after the initial build, Next.js will attempt to re-generate the page and fetch the latest blog posts after the revalidation interval (60 seconds in this example).
When a user visits the homepage again after the revalidation interval, Next.js will serve the previously generated static page. However, in the background, Next.js will make an API request to fetch the latest blog posts.
Once the API request is complete, Next.js will re-render the HomePage component with the updated data and cache it for subsequent requests.

By utilizing ISG in this example, you ensure that the blog post list on the homepage remains up-to-date while still providing the benefits of static page generation for improved performance.

Remember to customize the example to suit your specific needs, such as integrating with your own API or database to fetch the blog posts data.

Conclusion

Incremental Static Generation (ISG) is a powerful feature in Next.js that combines the benefits of Static Generation with the ability to update static pages at runtime. It allows you to have fast-loading, pre-rendered pages while still delivering real-time data to users. By implementing ISG, you can achieve better performance, improved user experience, and reduced server load. Next.js continues to innovate and provide developers with the tools they need to build modern, scalable web applications.