Server-Side Rendering (SSR) vs Client-Side Rendering (CSR) in React

When building React applications, one of the most important architectural choices is how your app renders: on the server or in the browser. Both approaches—Server-Side Rendering (SSR) and Client-Side Rendering (CSR)—come with trade-offs that directly impact performance, SEO, and user experience.

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Client-Side Rendering (CSR)

In CSR, the browser receives a mostly empty HTML file and loads JavaScript bundles. React then builds the UI on the client.

How it works:

1. The user requests the page.
    
2. Server returns an HTML shell + JS bundle.
    
3. Browser downloads JS, React hydrates the DOM, and UI appears.
    

Pros:

• Great for rich, interactive apps (SPAs).
   
• Less server load, since most work happens in the browser.
   
• Simplifies deployment (static hosting works).
   

Cons:

• Slower first load (blank screen until JS executes).
   
• SEO challenges, since crawlers may not wait for JS to render content.

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Server-Side Rendering (SSR)

In SSR, React runs on the server. The server sends fully rendered HTML, which the browser displays immediately. React then hydrates it to make it interactive.

How it works:

1. The user requests the page.
    
2. Server executes React code, generates HTML.
    
3. Browser shows HTML instantly, then downloads JS to hydrate interactivity.
    

Pros:

• Faster initial load (users see content sooner).
   
• Better SEO (HTML content is ready for crawlers).
   
• Works well for content-heavy or marketing pages.
   

Cons:

• Higher server load (must render per request).
   
• Slightly more complex setup (needs Node.js server or frameworks like Next.js).
   

When to Use Which?

• CSR: Best for dashboards, apps with heavy interactivity, and logged-in user flows.
   
• SSR: Best for e-commerce, blogs, landing pages, or apps where SEO and first-paint speed matter.
   

 React + Tools for SSR

• Next.js → most popular framework for SSR with React.
   
• Remix → full-stack framework focusing on server rendering.
   

Takeaway:

If your app depends on fast content delivery and SEO, choose SSR. If it’s highly interactive with less SEO needs, CSR is often simpler. Many modern React apps combine both (using frameworks like Next.js for SSR + CSR for dynamic parts).