Understanding Incremental Static Generation in Next.js: A Practical Guide

Introduction

Static generation has revolutionized the way developers build web applications, making sites faster, more efficient, and highly scalable. But what happens when your site’s content frequently changes? Enter Incremental Static Generation (ISG) in Next.js—a powerful feature that blends the best of static and dynamic site generation. This blog post will dive into the concept of Incremental Static Generation, explaining what it is, how it works, and how to implement it in your Next.js applications.

Target Audience:

This guide is designed for developers familiar with JavaScript and React who want to optimize performance and SEO for their Next.js applications by using Next.js’s static generation capabilities.

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Table of Contents

1. What is Incremental Static Generation (ISG)?

2. How Incremental Static Generation Works in Next.js

3. Benefits of ISG

4. Implementing ISG in Next.js

5. When to Use Incremental Static Generation

6. Limitations and Best Practices

7. Conclusion

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1. What is Incremental Static Generation (ISG)?

Incremental Static Generation (ISG) is a feature in Next.js that allows you to create and update static pages after the initial build, in real-time. With ISG, Next.js pre-renders pages at build time, but it can also update pages incrementally, after a specified revalidation period. This hybrid approach combines the performance benefits of static generation with the flexibility of server-rendered pages.

Why ISG Matters

• Content Freshness: Ensures that content like blog posts, product pages, and news articles stay current.

• Scalability: Ideal for applications with a large number of pages, as it doesn’t require a full rebuild to update content.

• SEO Optimization: Provides the benefits of SEO with pre-rendered, crawlable pages while still allowing for content updates.

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2. How Incremental Static Generation Works in Next.js

In traditional static generation, Next.js generates all pages at build time, which can be slow and challenging if your content changes often. With ISG, Next.js introduces a revalidation process, where pages are statically generated initially, then updated incrementally at runtime based on a specified interval.

Key Concept: Revalidation

• The revalidate option in Next.js determines how often a page should be updated.

• When a user visits a page that needs updating, Next.js will regenerate that page in the background while continuing to serve the cached version to the visitor.

• Future visitors receive the newly generated page after the revalidation period.

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3. Benefits of ISG

Incremental Static Generation offers multiple benefits for developers and end-users alike:

• Improved Performance: Pages are served as static files, leading to faster load times and better performance.

• Reduced Build Times: By only updating pages that need it, ISG avoids full rebuilds, making it efficient for large applications.

• SEO Friendliness: Pages are pre-rendered, ensuring that search engines can crawl and index them.

• Dynamic Flexibility: Content can change over time without requiring a full re-deployment, ideal for sites with frequently updated information.

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4. Implementing ISG in Next.js

Let’s walk through a simple implementation of Incremental Static Generation in Next.js using the getStaticProps function.

Step 1: Set Up getStaticProps

In your Next.js component, use the getStaticProps function to fetch data at build time.

export async function getStaticProps() {
  const data = await fetchData();
  return {
    props: { data },
    revalidate: 10, // Revalidate the page every 10 seconds
  };
}

Here, the revalidate property specifies that Next.js should check for updated data every 10 seconds and regenerate the page if necessary.

Step 2: Displaying the Data

Use the fetched data in your component to display the content

export default function MyPage({ data }) {
  return (
    <div>
      <h1 id="data-title">{data.title}</h1>
      <p>{data.content}</p>
    </div>
  );
}

With this setup, the page will be pre-rendered at build time, and after the specified revalidation period, Next.js will fetch fresh data and update the page in the background.

Step 3: Testing the ISG Setup

Deploy your Next.js application and observe the behavior:

1. Note the initial build time.

2. Check how the content refreshes based on the revalidate interval.

3. Confirm that users always see the latest version without refresh delays.

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5. When to Use Incremental Static Generation

ISG isn’t the right solution for every project. Here are cases where ISG can be particularly beneficial:

• Blogs and News Sites: For content that needs periodic updates without full rebuilds.

• E-commerce: Product pages where prices or inventory may change frequently.

• Documentation: Sites that need frequent updates while keeping low build times.

• Content-Heavy Sites: Websites with a large number of pages where a full rebuild would be impractical.

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6. Limitations and Best Practices

While ISG offers significant advantages, there are also some limitations to keep in mind:

• Caching Inconsistencies: Users may briefly see outdated content before the updated page is served after revalidation.

• Data Fetching Limitations: Real-time data that must be up-to-the-second (like live scores) is better suited to server-side rendering.

• Performance Considerations: Each regeneration uses server resources, so the revalidation interval should be balanced based on update needs and available resources.

Best Practices:

• Choose an appropriate revalidate interval based on the content’s freshness needs.

• Use ISG selectively, only on pages that benefit from periodic updates.

• Monitor revalidation usage to avoid unnecessary server load.

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7. Conclusion

Incremental Static Generation in Next.js provides a hybrid approach to building web applications that need to be fast, scalable, and SEO-friendly while handling frequently updated content. By using ISG, developers can leverage the advantages of static generation and on-demand revalidation to create a dynamic, content-rich experience. Whether you’re running an e-commerce site, a blog, or a documentation portal, ISG can improve both the user experience and backend efficiency.

Key Takeaway: ISG allows you to deliver content that’s always up-to-date without sacrificing performance or SEO—a win-win for modern web applications.

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Further Reading

• Next.js Documentation on Incremental Static Regeneration

• Static vs Server-Side Rendering in Next.js

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