Published at: November 12, 2021
As a React developer, when you start working with frameworks like Next.js, you’ll encounter two key methods for rendering content: Server-Side Rendering (SSR) and Static Site Generation (SSG). Both are used to pre-render your pages for improved performance and SEO, but which one should you choose for your next project?
In this post, we’ll explore the differences between SSR and SSG, their benefits, and how to decide which one to use in your Next.js app.
1. What is Server-Side Rendering (SSR)?
Server-Side Rendering (SSR) refers to the process where React pages are rendered on the server at the time of the request. When a user visits a page, the server generates the HTML for that page on the fly and sends it to the client. The React app then takes over on the client side, making it fully interactive.
Benefits of SSR:
- Fresh Data: SSR allows you to always display the latest data since the HTML is generated for each request, ensuring content is up-to-date.
- SEO Advantages: Because the HTML is generated on the server, search engine crawlers can easily index the fully rendered page, improving SEO.
When to Use SSR:
- Dynamic Content: If your app has content that changes frequently, SSR can ensure that your users see the most recent data every time they visit.
- Personalized Experiences: If the content needs to be tailored to individual users, such as a dashboard or user profile page, SSR can dynamically load user-specific information from the server.
2. What is Static Site Generation (SSG)?
Static Site Generation (SSG) is the process where React pages are pre-rendered at build time. In this approach, the HTML is generated once when you build your app, and the resulting HTML files are served to all users, regardless of when they visit the site.
Benefits of SSG:
- Blazing Fast Performance: Since the HTML is pre-built and served as static files, the page loads almost instantly when the user requests it. There’s no need to wait for the server to generate the page on the fly.
- Cost-Effective: SSG typically requires fewer server resources because the pages are static and don’t need to be generated dynamically for each request.
- Great for SEO: Like SSR, SSG provides fully-rendered HTML that can be easily indexed by search engines.
When to Use SSG:
- Content That Doesn’t Change Often: SSG is ideal for blogs, portfolios, or marketing pages where the content remains mostly static and doesn’t change frequently.
- Performance-Critical Apps: If the app needs to be extremely fast and responsive, SSG is a great choice because static pages are delivered quickly, reducing load times.
- SEO-Friendly Sites: Like SSR, SSG also benefits from great SEO because the content is pre-rendered.
3. SSR vs. SSG: Key Differences
| Feature | Server-Side Rendering (SSR) | Static Site Generation (SSG) |
|---|---|---|
| Page Rendering | On the server at runtime | At build time |
| Performance | Slower load times (on first request) | Fast load times (instant) |
| Data Freshness | Always fresh on each request | Can be stale (depends on re-building) |
| SEO | Excellent SEO | Excellent SEO |
| Use Case | Dynamic content, user personalization | Blogs, documentation, static pages |
4. Performance and SEO Considerations
Performance:
- SSR: The main disadvantage of SSR is that the HTML needs to be generated for every user request, which can cause slower load times, especially if the server is busy or if there’s a lot of dynamic content to load.
- SSG: Since the HTML is pre-built, SSG pages are incredibly fast to load. However, the data might not be the most up-to-date if your content changes frequently.
SEO:
Both SSR and SSG offer significant SEO benefits because the HTML is rendered on the server before it is sent to the browser. This allows search engine crawlers to fully index the page, making it more discoverable.
- SSR: Since each request generates the most up-to-date HTML, SSR is great for pages with rapidly changing content that must be indexed.
- SSG: SSG also provides SEO benefits, especially for content that doesn’t change frequently. Static pages are indexed quickly and efficiently.
5. How to Choose Between SSR and SSG in Next.js
In Next.js, the choice between SSR and SSG is made at the page level, and you can configure each page according to its needs. Here’s a quick guide:
- Use SSR (getServerSideProps) if:
- You need fresh data on every request.
- The content is highly dynamic (e.g., user-specific data).
- Your app requires server-side logic for rendering the page.
- Use SSG (getStaticProps) if:
- Your content is static or doesn’t change often.
- You want the fastest possible page load times.
- SEO is important, and you don’t need to load fresh data on every request.
Here’s an example of how to implement each in Next.js:
SSR Example:
// pages/ssr-example.js
export async function getServerSideProps() {
// Fetch dynamic data on each request
const res = await fetch('https://api.example.com/data');
const data = await res.json();
return { props: { data } };
}
const SSRExample = ({ data }) => {
return <div>Data: {JSON.stringify(data)}</div>;
};
export default SSRExample;
SSG Example:
// pages/ssg-example.js
export async function getStaticProps() {
// Fetch static data at build time
const res = await fetch('https://api.example.com/data');
const data = await res.json();
return { props: { data } };
}
const SSGExample = ({ data }) => {
return <div>Data: {JSON.stringify(data)}</div>;
};
export default SSGExample;
6. Conclusion
When deciding between SSR and SSG, consider your app’s requirements. If you have dynamic, personalized content or need real-time updates, SSR is likely the better choice. On the other hand, if your app consists of static content or can tolerate some delay in content updates, SSG will offer lightning-fast performance and a better user experience.
In Next.js, you can mix and match both approaches, using SSR for dynamic pages and SSG for static content, giving you the flexibility to build highly performant React applications.
