Next.js is a powerful React framework offering multiple rendering strategies to build highly performant and scalable applications. If you’re diving into Next.js, you’ve likely encountered terms like SSR (Server-Side Rendering), CSR (Client-Side Rendering), ISR (Incremental Static Regeneration), and Revalidate. In this blog, we’ll break down these terms, their purposes, and when to use them.

What is SSR (Server-Side Rendering)?

SSR means that your application generates HTML for a page on the server for every incoming request. The server fetches the data, renders the page, and sends it to the client.

Use Cases for SSR:

• Pages that need dynamic data for each request, like dashboards or user profiles.
• SEO-critical pages where the content depends on user input or query parameters.

Example in Next.js:

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

    return {
        props: { data }, // Pass data to the page
    };
}

This approach ensures the data is fresh on every request, making it ideal for frequently updated content.

What is CSR (Client-Side Rendering)?

In CSR, the page loads minimal HTML and JavaScript, and the browser fetches data and renders the content entirely on the client-side.

Use Cases for CSR:

• Pages where SEO isn’t a priority, like dashboards or admin panels.
• Applications with fast client-side interactions that rely heavily on user interaction.

Example in Next.js:

import { useEffect, useState } from 'react';

function Page() {
    const [data, setData] = useState(null);

    useEffect(() => {
        fetch('https://api.example.com/data')
            .then((res) => res.json())
            .then((data) => setData(data));
    }, []);

    if (!data) return <p>Loading...</p>;

    return <div>{JSON.stringify(data)}</div>;
}

export default Page;

CSR is lightweight for the server but might take longer to render the content due to the client-side fetch.

What is ISR (Incremental Static Regeneration)?

ISR combines the speed of static site generation (SSG) with the flexibility of dynamic content. With ISR, static pages are regenerated at runtime after a set time interval, ensuring your app stays up-to-date without needing full re-deployment.

Use Cases for ISR:

• Blogs, e-commerce, or marketing sites with periodically updated data.
• When fast load times are essential, but data can be slightly stale.

Example in Next.js:

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

    return {
        props: { data },
        revalidate: 10, // Revalidate the page every 10 seconds
    };
}

Here, Next.js generates the page during the build process and regenerates it in the background when a user accesses the page after the revalidate interval has expired.

What is Revalidate?

The revalidate key in ISR allows you to specify how often the static page should be updated. It ensures users always get slightly fresh data without server-side rendering for every request.

Key Features:

• Improves performance: Combines the speed of static pages with the flexibility of dynamic updates.
• SEO-friendly: Since pages are pre-rendered, search engines can crawl them easily.

Choosing the Right Rendering Strategy

Conclusion

Each rendering strategy in Next.js has its strengths and trade-offs. By understanding SSR, CSR, ISR, and revalidate, you can choose the right approach for your project based on factors like SEO, performance, and data freshness.

Leverage the flexibility of Next.js to build applications that balance speed, scalability, and user experience effectively. Whether you’re building a blog, an e-commerce platform, or a dashboard, Next.js has the right tools for you!

Happy coding! 😊