getStaticProps is a built-in function in Next.js used for Static Site Generation (SSG). It allows you to fetch data at build time, which means the data is generated into static HTML files when you build your application. This can improve performance and SEO since the content is pre-rendered and served as static files.

Key Features of getStaticProps

1. Static Generation: The data is fetched during the build process, making it available to the page when it is served. This results in faster page loads since the HTML is served directly without needing to fetch data on each request.

2. Build Time Data Fetching: You can use getStaticProps to fetch data from APIs, databases, or any other data source during the build phase.

3. Props Passing: The data fetched with getStaticProps is returned as props to the page component, making it easy to render content based on that data.

4. Incremental Static Regeneration (ISR): With Next.js 9.5 and later, you can use the revalidate property to specify a time interval after which a page re-generates in the background. This allows you to serve static pages while still keeping data fresh.

Basic Usage

Here’s how you can use getStaticProps in a Next.js page component:

// pages/index.js
export default function HomePage({ data }) {
  return (
    <div>
      <h1>Static Props Example</h1>
      <ul>
        {data.map(item => (
          <li key={item.id}>{item.name}</li>
        ))}
      </ul>
    </div>
  );
}

export async function getStaticProps() {
  // Fetch data from an API or any other source
  const res = await fetch('https://api.example.com/items');
  const data = await res.json();

  return {
    props: {
      data, // Pass data to the page component as props
    },
    // Optionally, you can specify a revalidate time
    revalidate: 10, // Re-generate the page at most once every 10 seconds
  };
}

Explanation of the Code

1. Page Component: The HomePage component receives data as a prop. This data is used to render a list of items.

2. getStaticProps Function:

   • This function is declared async, allowing you to use await for data fetching.
   • Inside this function, you can fetch data from an external API or any other data source.
   • After fetching the data, you return an object containing the props key. The value of props is an object that will be merged with the component's props.

3. Revalidation (Optional):

   • By adding the revalidate key in the return object, you can specify how often the page should be re-generated in the background. For example, revalidate: 10 means that Next.js will attempt to re-generate the page at most once every 10 seconds when a request comes in.

Benefits of getStaticProps

• Performance: Since the page is pre-rendered to static HTML, it loads faster compared to server-side rendering (SSR), where data is fetched on each request.

• SEO: Static pages can be indexed better by search engines since the HTML content is available immediately.

• Simplicity: getStaticProps provides a simple way to fetch data at build time, making it easy to create pages that do not change often.

Use Cases for getStaticProps

• Blog Posts: Fetching a list of blog posts from an API or CMS that do not change frequently.

• Product Pages: Generating product detail pages based on data from an e-commerce API.

• Documentation Sites: Building static documentation where content is mostly static.

Limitations

• Static Content: If your data changes frequently and you need real-time updates, consider using server-side rendering (getServerSideProps) or incremental static regeneration with revalidation.

• Build Time: The data is fetched at build time, so if your API is slow or there are many pages, it can increase the build time for your application.

Summary

getStaticProps is a powerful feature in Next.js for generating static pages with data fetched at build time. By leveraging this function, you can create fast, SEO-friendly pages while keeping the user experience smooth and responsive.