Imagine you’re a hungry diner with two restaurant options: one where the chef prepares your entire meal in the kitchen and serves it ready to eat (faster, but changes require a trip back to the kitchen), or one where you’re given raw ingredients to cook at your table, like Korean barbecue (slower to start, but easy to customize as you go).
Similarly, in web development, two prominent rendering techniques shape how and when web pages appear, or render, in the user’s browser: server-side rendering, or SSR (done on the web server before sending the page), and client-side rendering, or CSR (done in the user’s browser after receiving the page).
CSR shifts the workload to the user’s browser, easing the server’s burden but sometimes making the experience feel slower. SSR, by contrast, delivers a fully rendered, ready-to-view page from the server to the client’s browser, which can feel faster to the user.
Here are the key differences between server-side and client-side rendering.
What is server-side rendering (SSR)?
Server-side rendering (SSR) is when web pages load and render on a server, not the user’s device. The server builds the fully rendered HTML for a requested page—complete with the user interface and data—to the user’s browser, which displays the fully rendered page. The browser can then download any JavaScript needed to make the page more interactive.
SSR is ideal for ecommerce sites, landing pages, blogs, and content-heavy pages where search engine optimization (SEO) and quick page loads are key. Because the server sends a complete HTML page, the content shows up quickly and is easy for search engines to crawl and index.
That said, SSR can require more server resources, especially during high traffic, and it can feel less smooth in more dynamic apps (think Gmail, Google Docs, to-do apps like Notion), since every reload requires a fresh server request. You can work around this with techniques like websockets (for real-time server-client communication) or client-side state management (like storing cookies or using hidden fields to store data), which can lead to reduced server load.
What is client-side rendering (CSR)?
Client-side rendering (CSR) shifts the work of building and displaying web pages—including the HTML content and user interface (UI)—to the user’s browser. When a page is requested, the server sends a minimal, almost empty HTML file, and the browser downloads JavaScript code that handles how the page looks and behaves. That JavaScript then pulls in content—typically via application programming interfaces (APIs)—and renders it directly in the user’s browser.
CSR lets you create smoother, app-like experiences like chat apps, social media feeds, and dashboards. It’s especially useful for single-page applications (SPAs), where users interact with one page and only parts of the content change without reloading.
The downside is that CSR can take longer to fully display content, especially on slower devices and connections. It’s also less SEO-friendly, as search engines may have difficulty indexing JavaScript-rendered pages (though this is improving). For simple, static pages, CSR may be more than you need.
SSR vs. CSR: What’s the difference?
- Where the content is rendered
- Initial page load
- Interactivity
- Search engine optimization
- Server load
Both rendering methods deliver the necessary data, content, and user interface from the server to the user’s browser—just in different ways. Modern websites often combine both approaches, serving the initial page through SSR for speed, then switching to CSR for smooth interactions afterward—like getting your appetizer from the chef but cooking the main course yourself.
Here are the key differences between SSR and CSR:
Where the content is rendered
In SSR, both the content and user interface are rendered on the server before being sent to the browser. JavaScript can still enhance interactivity afterward, but the main structure and data are already in place. This results in faster initial load times and more consistent layouts across different devices, though it requires the server to process every request, which could demand more infrastructure as your traffic scales.
In CSR, content is rendered in the user’s browser. JavaScript fetches data from the server and loads it into the browser after the initial, minimal HTML is delivered. This approach reduces server load and gives the browser more control over the user interface. However, it does require JavaScript to be enabled and can delay content visibility until scripts finish loading.
Initial page load
With SSR, everything—content and interface—arrives at the user’s browser all at once. Since the page is fully formed when it reaches the browser, users see content faster, improving the time it takes for content to show up on screen and creating a perception of better performance. The downside here is navigation between pages can feel slower, and if server rendering lags or relies on post-load JavaScript, it can introduce delays.
CSR, on the other hand, quickly sends a lightweight HTML file, but users have to wait for JavaScript to download, fetch data, and render the page, so the content appears more slowly at first. But once loaded, CSR offers faster navigation within the app, since the browser handles updates without full page reloads.
CSR can seem slower to users who have to wait for the JavaScript to download, fetch, and execute the data before it shows up fully on screen. It’s good for subsequent navigation, though, since the JavaScript is loaded and running in the user’s browser.
Interactivity
SSR can feel faster at first because users see content immediately. But dynamic elements like buttons or forms won’t work until the JavaScript finishes loading and “hydrates” the static HTML. Hydration bridges the gap between fast first loads of SSR and the more interactive capabilities of CSR.
CSR is generally well-suited for web development of interactive apps like chat rooms, real-time data dashboards, or interfaces with drag-and-drop functionality. Since the browser handles all the rendering, updates or transitions happen without having to reload the page from a web server, making for a more fluid, app-like experience. The tradeoff is that users don’t see any content until the JavaScript code is fully downloaded and parsed, which can lead to a brief flicker or delay before the page becomes usable.
Search engine optimization (SEO)
SSR pages include all the content directly in the HTML sent to the browser, which also makes it easier for search engines like Google to crawl and rank the page. This makes SSR great for SEO-critical content like blogs or other informational sites. However, handling personalized or user-specific content is more complex, since it delivers a fully rendered HTML page prior to delivery. To show personalized data, you’ll need to capture user data before rendering the page.
CSR can be more difficult for search engines to index, because the content isn’t available in the initial HTML—it only appears after JavaScript runs in the browser. This delay can make it harder for search engines to index the page, especially for content-heavy or search-dependent websites. That said, solutions like pre-rendering, static generation, or hybrid rendering can help mitigate this, and search engines keep getting better at indexing JavaScript-rendered pages.
Server load
With SSR, the server processes the request itself, builds an HTML page, and delivers it in real time. This requires more server resources, especially under heavy load, like heavy traffic or with complex web pages. To optimize performance, caching and techniques like database query optimization or parallel data fetching might be necessary.
With CSR, most of the work happens in the user’s browser. The server only needs to send static files or respond to API data requests, which reduces the load on the web server and makes it easier (and cheaper) to scale. However, this can put a strain on users with older or less powerful devices, as they’re doing more of the processing.
SSR vs. CSR FAQ
Is SSR always better than CSR?
The short answer is no. Each approach has its own strengths and is better for different types of web pages. SSR is better for sites where SEO and fast initial load matter and where content changes per request but doesn’t need to be highly interactive. CSR is better for highly interactive apps that don’t prioritize SEO as much and place less demand on the server.
Is CSR or SSR better for SEO?
While search engines are getting better at indexing post-delivery content, server-side rendering is still better for search engine optimization. The web page is delivered directly to users (and search engine bots), so there’s a more direct connection.
How can you check if a page is SSR or CSR?
First, view the page source and see if the content (headers, text, titles, product names) is there or if it’s mostly placeholders (things like (
). The former generally means it’s using SSR, while the latter can mean it’s using CSR. You can also disable JavaScript on your browser and see if the page still shows the content. If so, it’s SSR. If not, then it’s using CSR. Additionally, you can use DevTools’ Network Tab to see if there is real content or a shell with place holders. Like the page source, real content indicates SSR, while placeholders indicate CSR.
