SSR vs. CSR vs. SSG: A Comprehensive Comparison of Web Rendering Strategies
by Hugo Valcourt, Founder, Senior Front-end Developer
1. SSR (Server-Side Rendering)
Description:
In SSR, the server generates the HTML for a webpage and sends it to the client. This means that the initial page load is rendered on the server and delivered fully formed to the browser, allowing for quicker content visibility.
How it works:
When a request is made to the server, the server fetches the necessary data, compiles the page, and sends the HTML to the client.
Afterward, JavaScript on the client-side can "hydrate" the page to make it interactive.
Advantages:
Faster Time to First Paint: The HTML is fully generated on the server and sent to the client, so users see content faster, improving SEO and user experience.
Better SEO: Since the full content is served as HTML initially, search engine crawlers can easily index the content.
Supports Dynamic Content: SSR can generate dynamic pages based on real-time data.
Disadvantages:
Higher Server Load: Each request results in server-side processing, increasing server load and response times under high traffic.
Slower Interactions Post-Load: After the initial render, the page may take longer to become fully interactive because of the JavaScript hydration process.
Increased Latency: Each new page request requires server-side rendering, so there might be delays in responding to multiple user interactions.
2. CSR (Client-Side Rendering)
Description:
In CSR, the server only sends a bare-bones HTML document and JavaScript files. The content of the page is rendered by the client’s browser after downloading and executing the JavaScript. This approach is typically used with Single Page Applications (SPAs).
How it works:
The server sends a minimal HTML file.
The client downloads the necessary JavaScript, which fetches data from APIs, processes it, and then renders the content in the browser.
Advantages:
Rich Interactivity: The client handles everything, so interactions can be more dynamic, allowing for complex user interfaces and smoother experiences.
Reduced Server Load: After the initial request, the server doesn't need to re-render pages, reducing the burden on the backend.
Efficient for SPAs: Once the JavaScript is loaded, navigation between different parts of the site is fast and smooth.
Disadvantages:
Poor SEO: Search engine crawlers may struggle to index the content if JavaScript is required to generate it.
Slower Initial Load: The browser must download and execute JavaScript before the content is displayed, leading to slower time-to-first-paint compared to SSR.
Performance Issues: Large amounts of JavaScript can slow down performance, particularly on mobile devices with less processing power.
3. SSG (Static Site Generation)
Description:
SSG generates all the HTML at build time, rather than on-demand or client-side. Pages are pre-rendered into static HTML and can be served by a Content Delivery Network (CDN). This is great for websites with content that doesn’t change frequently.
How it works:
When the website is built (e.g., during a deployment process), the system generates all pages as static HTML files that are served directly to users.
Advantages:
Ultra-Fast Performance: Because the pages are static, they can be served instantly, often from a CDN, leading to minimal load times.
Highly Scalable: Static sites require very little server power, and traffic spikes don’t significantly increase server load.
Great SEO: Since the content is pre-rendered as HTML, it's easy for search engines to crawl and index the pages.
Security: There's less risk of server-side vulnerabilities since there’s no need to run server-side code for every request.
Disadvantages:
Not Suitable for Dynamic Content: SSG is less suitable for websites that rely on frequently changing data (e.g., user-specific dashboards or real-time updates).
Build Time Increases with Content Size: The more pages you need to generate, the longer your build process becomes, which can slow down deployments.
Content Staleness: If the site content changes frequently, it can be outdated until the next rebuild is triggered.
Summary Table
Rendering Method | Key Feature | Advantages | Disadvantages |
SSR | HTML rendered on server | Fast initial load, good for SEO, supports dynamic content | Higher server load, potential latency |
CSR | HTML rendered on client | Rich interactivity, reduced server load, fast SPA navigation | Slower initial load, poor SEO, performance issues |
SSG | HTML pre-rendered at build time | Ultra-fast performance, great scalability, good SEO, secure | Not ideal for dynamic content, slow builds for large sites |
Conclusion:
SSR is great for dynamic websites where SEO and fast initial content load are critical, but it can be resource-intensive.
CSR is ideal for SPAs with complex interactivity but suffers from slower initial loads and SEO challenges.
SSG excels in performance, scalability, and SEO for static content but lacks flexibility for frequently updated or personalized pages.