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Static, Dynamic, or ISR? Choosing the Best Rendering Strategy for Next.js Projects

When building a web project in Next.js, one of the most important decisions you'll make is how your pages are rendered. Next.js offers three main rendering strategies: Static Site Generation (SSG), Server-Side Rendering (SSR), and Incremental Static Regeneration (ISR). Each option has its strengths and ideal use cases, so understanding them can help you create fast, scalable, and user-friendly web applications.

Let’s explore these strategies, when to use them, and how they impact your project’s performance and user experience.

1. Static Site Generation (SSG)

Static Site Generation pre-renders your pages at build time. This means Next.js generates HTML files when you build your application, and these files are served to users whenever they visit your site.

Use Cases for SSG:

• Blog posts
• Marketing pages
• Documentation

Key Benefits of SSG:

• Speed: Pages are served as static files, leading to near-instant loading times.
• SEO-Friendly: Search engines can easily crawl and index fully-rendered HTML.
• Cost Efficiency: No need for a server to handle rendering requests.

Here’s how you might use SSG in a blog:

// pages/blog/[slug].tsx

import { GetStaticProps, GetStaticPaths } from 'next';

export const getStaticPaths: GetStaticPaths = async () => {
  const posts = await fetch('https://api.example.com/posts').then((res) => res.json());
  return {
    paths: posts.map((post) => ({ params: { slug: post.slug } })),
    fallback: false, // Only pre-render paths defined here
  };
};

export const getStaticProps: GetStaticProps = async (context) => {
  const { slug } = context.params!;
  const post = await fetch(`https://api.example.com/posts/${slug}`).then((res) => res.json());
  return {
    props: { post },
  };
};

const BlogPost = ({ post }: { post: any }) => (
  <article>
    <h1>{post.title}</h1>
    <p>{post.content}</p>
  </article>
);

export default BlogPost;

This setup pre-renders your blog pages during the build process, making them lightning-fast for users.

2. Server-Side Rendering (SSR)

Server-Side Rendering generates the HTML for each request on the server, ensuring users get the most up-to-date content.

Use Cases for SSR:

• User-specific dashboards
• Real-time data feeds
• Applications requiring high personalization

Key Benefits of SSR:

• Dynamic Content: Each request fetches the latest data.
• Real-Time Updates: Ideal for data that changes frequently.

For example, here’s how you might create a user dashboard with SSR:

// pages/dashboard.tsx

import { GetServerSideProps } from 'next';

export const getServerSideProps: GetServerSideProps = async (context) => {
  const userData = await fetch('https://api.example.com/user', {
    headers: { Authorization: `Bearer ${context.req.cookies.token}` },
  }).then((res) => res.json());

  return {
    props: { userData },
  };
};

const Dashboard = ({ userData }: { userData: any }) => (
  <div>
    <h1>Welcome, {userData.name}!</h1>
    <p>Your account balance is ${userData.balance}</p>
  </div>
);

export default Dashboard;

This approach ensures each user sees personalized, up-to-date information.

3. Incremental Static Regeneration (ISR)

ISR combines the best of both worlds: the speed of SSG with the flexibility of SSR. With ISR, you can update static pages at runtime without needing a full rebuild.

Use Cases for ISR:

• E-commerce product pages
• News articles
• Content-heavy sites with frequent updates

Key Benefits of ISR:

• Scalability: Static pages are served quickly, reducing server load.
• Dynamic Updates: Fresh content is generated on demand based on a defined revalidation interval.

Here’s how you could use ISR for a product page:

// pages/product/[id].tsx

import { GetStaticProps, GetStaticPaths } from 'next';

export const getStaticPaths: GetStaticPaths = async () => {
  const products = await fetch('https://api.example.com/products').then((res) => res.json());
  return {
    paths: products.map((product) => ({ params: { id: product.id.toString() } })),
    fallback: 'blocking', // Render page on the server if not pre-generated
  };
};

export const getStaticProps: GetStaticProps = async (context) => {
  const { id } = context.params!;
  const product = await fetch(`https://api.example.com/products/${id}`).then((res) => res.json());
  return {
    props: { product },
    revalidate: 60, // Revalidate the page every 60 seconds
  };
};

const ProductPage = ({ product }: { product: any }) => (
  <div>
    <h1>{product.name}</h1>
    <p>{product.description}</p>
    <p>Price: ${product.price}</p>
  </div>
);

export default ProductPage;

With ISR, product pages stay current without sacrificing speed or scalability.

Comparing the Strategies

Static Site Generation (SSG):

If your pages don’t change frequently and speed is critical, SSG is the ideal choice. However, it requires a rebuild to reflect updates unless paired with ISR.

Server-Side Rendering (SSR):

When content changes dynamically or needs to be personalized per user, SSR is a better fit. Be mindful of its higher server costs and potentially slower load times.

Incremental Static Regeneration (ISR):

ISR offers a balance between speed and dynamism. It’s perfect for sites with semi-frequent updates, ensuring scalability and performance.

Which Should You Choose?

The right strategy depends on your project’s specific needs. Here are some quick tips:

• Use SSG for blogs, marketing pages, and static content.
• Opt for SSR for dashboards, real-time data, or personalized pages.
• Leverage ISR for content-heavy or frequently updated sites where speed is crucial.

Don’t forget—you can mix and match! For example, a site can use SSG for its homepage, SSR for its admin panel, and ISR for its product pages.

Conclusion

Selecting the right rendering strategy in Next.js boils down to understanding your project’s goals and your users’ needs. Whether you prioritize speed, data freshness, or scalability, Next.js gives you the flexibility to build a solution that fits. Experiment with different strategies and analyze performance metrics to optimize your app’s user experience.