Basics of Server-Side Rendering

Anton Ioffe - October 24th 2023 - 9 minutes read

In the ever-evolving world of web development, understanding and harnessing the power of Server-Side Rendering (SSR) can set you apart from the crowd. This comprehensive article pledges to take you on a journey exploring the depths of SSR in modern web development. We'll delve into the critical roles of JavaScript, deconstruct SSR workflows, and dissect the strengths, limitations and best practices associated with Server-Side Rendering. We'll also throw in an invaluable head-to-head comparison with client-side rendering that might just have you reconsidering your current strategies. So strap in, as we demystify SSR and share insights that promise to elevate your development game.

Understanding Server-Side Rendering (SSR) in Modern Web Development

Server-Side Rendering (SSR) is a critical aspect of modern web development, particularly in the realm of single-page applications. In the SSR approach, web pages are fully rendered on the server before they are sent to the browser. This behavior diverges from client-side rendering, where the JavaScript engine in the browser is responsible for generating the HTML page from data fetched from the server. In SSR, upon a user’s request, the server executes the JavaScript code to generate the HTML markup and sends this ready-to-render HTML document along with the CSS to the client's browser. The browser can then immediately display the fully-rendered page to the user, even as it downloads and processes additional JavaScript for interactivity.

Let's dive deeper into HOW this process unfolds. The server receives an HTTP request from the client (user’s browser). It then fetches the requisite data from the database or third-party APIs, and generates a fully-rendered HTML page using the received data. The server promptly sends this pre-rendered page to the client as its HTTP response to the initial request. By unburdening the client's machine and taking the bulk of the load onto itself, the server essentially ensures that the user sees a fully-rendered, interactive page promptly upon request.

The importance of JavaScript in SSR cannot be overstated. Modern JavaScript frameworks such as React.js or Angular.js, with server-render capabilities, are often the go-to choices for implementing SSR. These frameworks render the JavaScript components into a fully-detailed HTML on the server side. Essentially, the same JavaScript code is executed on both the server and the client-side (hence the term 'universal rendering'). Developers should note however, that while server-side rendered applications can provide a faster initial page load and are generally better for SEO, their first interaction may be slightly slower due to the additional time taken by the browser to download and parse the JavaScript for interactivity.

Finally, let's delve into SSR's role in modern single-page applications (SPAs). SPAs rely heavily on client-side rendering, wherein the JavaScript bundle interacts with the DOM to create and manage web content dynamically. This results in seamless user experiences akin to traditional desktop applications. Introducing SSR into SPAs can power them with the best of both worlds – the fast initial load times of traditional multi-page websites, and the rich interactions offered by client-side rendered applications. To sum up, understanding SSR allows for judicious use of rendering techniques depending on the needs of the web application at hand, contributing significantly to the optimization of user experience and load performance.

Breaking Down SSR Workflows and Techniques

Server-Side Rendering (SSR) is a server-centric rendering technique where the HTML page is compiled on the server and shipped off to the browser. This process can be broken down into four primary stages. The first stage initiates when the client's browser sends an HTTP request to the server. In JavaScript, this can be expressed as:

const http = require('http');

http.createServer((request, response) => {
    // handle request here

The http module in Node.js creates a new server that listens on port 8080. Here, the server is ready to process incoming requests.

After the server receives the client's HTTP request, the second stage initiates. This is where the server fetches any required data from a database or third-party APIs to be injected into the HTML template. This process is known as pre-rendering. For this task, you'd likely utilize an Express.js application with EJS as the template engine. The code could look similar to this:

app.get('/', async function (req, res) {
    const fetchedData = await fetchDataFromDB();
    res.render('index', {data: fetchedData});

In the above snippet, Express.js is running a GET request at the server root ('/'), fetching data via the fetchDataFromDB() function (which in turn handles communication with a database or API), and then pre-renders the 'index' view with the fetched data.

Next, the server compiles the JavaScript components into static HTML. This is the third stage of SSR, where a fully formed HTML document is generated server-side, ready to be sent to the client. Once the HTML is prepared, it's time for the fourth and final stage: the server's HTTP response. Here, the server sends the fully rendered HTML document to the client.

response.writeHead(200, {'Content-Type': 'text/html'});

In the above code, first, the server writes the HTTP response's headers, setting the status code to 200 and the Content-Type to text/html. Then, the server writes the rendered HTML to the response body. Finally, it ends the response, effectively sending the HTML document to the client.

In summary, SSR involves a step-by-step process where the server receives the client's HTTP request, fetches any necessary data, pre-renders the HTML with this data, and finally sends this fully rendered HTML back to the client. Each of these steps can come with its own challenges and considerations, but they all work together to ensure a fast initial page load and a significant initial render to the user's browser.

Analyzing Strengths and Limitations of Server-Side Rendering

Server-side rendering (SSR) indeed brings several benefits worth considering, with its notable impact on load time, user experience, and SEO. Owing to SSR's ability to only update the parts of the HTML that need updating, faster page transitions and a swifter First Contentful Paint (FCP) can be achieved. This results in an enhanced user experience, as even users stuck with slow internet connections or outdated devices can interact with your webpages without unnecessary delay. The SEO advantages of SSR also cannot be overstated - it enables the easier crawling and indexing of content, thereby enhancing the webpage's visibility to search engines.

That said, harnessing the benefits of SSR presents a few challenges too. Significantly, as your application grows, your server will bear the full burden of requests, both from users and bots. Rendering bigger, more complex applications on the server side can increase the loading time, the server operating as a single bottleneck. This higher server load isn't just a technical challenge; it can also lead to increased expenses. For example, you would need to use your company's server to host the SSR application, which means higher running costs.

Furthermore, some compatibility issues can arise when working with SSR. It can sometimes result in inefficient caching or cause issues with some devices or browsers if not implemented carefully. Additionally, given the complexity of maintaining and debugging SSR applications, further complications may arise.

All this points to an important understanding: While SSR brings undoubtedly substantial benefits, it also necessitates careful consideration in the context of your specific project requirements. Therefore, is the faster load time and SEO benefits worth the potential increase in server load, running costs, and application complexity? Your answer to this question would determine if SSR is the most suitable solution for your web application. So, does your current project justify the implementation of server-side rendering?

SSR Vs. Client-side Rendering: A Comparison

When comparing server-side rendering (SSR) and client-side rendering, it's essential to consider factors like performance, usability, SEO, and brand image. Let's examine each of these in turn.

Performance: SSR fetches and renders the HTML file on the server before delivering it to the client, resulting in quicker initial load times and an improved user experience on the first visit. However, it comes with the tradeoff of slower interactivity due to the need to download JavaScript files for interactive features. On the contrary, client-side rendering may result in slower initial load times but can offer faster interactivity as the browser has already loaded all the necessary JavaScript files.

Usability: All elements in a webpage rendered by SSR are loaded by the server, allowing them to appear onscreen faster. This is often advantageous in creating an initially impressive user experience. On the downside, the page is not interactive until all JavaScript files have been loaded, which could potentially delay user interaction. Conversely, a client-side rendered page may take longer to display all elements but becomes interactive sooner as the scripts are loaded and executed as they are downloaded.

SEO Impact: SSR has a significant advantage over client-side rendering when it comes to SEO. Server-side rendered content is easier for search engine crawlers to interpret and index, due to the fully rendered HTML delivered to the client. On the other hand, client-side rendering relies on JavaScript to fetch data and generate HTML, a process that may not be fully accounted for by all search engine tools.

Brand Image: Page loading speeds can influence the perception of a brand, especially given user expectations for fast and responsive web experiences. SSR can provide a more frictionless user experience upon first load, creating a positive impression, while slower initial loads with client-side rendering might affect the user's view of the brand negatively.

Yet, the choice isn't as binary as it might appear. Can we leverage the strengths of both SSR and client-side rendering with progressive enhancement or a hybrid rendering strategy? Could we render critical parts of an application on the server to benefit initial load times and SEO and defer less critical parts to client-side rendering for faster interactivity? It might be time to rethink existing development strategies and embrace more adaptable, flexible approaches to rendering in modern web development.

Avoiding SSR Pitfalls: Proven Strategies and Best Practices

One common mistake while implementing Server-Side Rendering (SSR) is not properly optimizing the server load, especially for bigger applications. To avoid this, developers must carefully plan the server capacity in accordance with the expected user load, and regularly monitor the server performance. Additionally, the load can be balanced across multiple servers using technologies like load balancers and containers.

Another frequent issue stems from non-optimized caching. As every page's HTML in SSR is unique, it becomes harder for content delivery networks (CDN) to cache, potentially causing longer page load times for users. However, to combat this, developers can leverage strategies like edge caching and service workers, strategically cache dynamic parts of the page, or use a CDN provider that supports HTML caching.

SSR is often associated with higher running costs due to the requirement of using your own company's server. This is true to an extent, but there are multiple cost-optimization strategies available. Opting for a serverless architecture, using dynamically scalable cloud solutions, or implementing on-demand SSR (hydrating only the necessary components) can help in reducing costs.

Lastly, developers often face compatibility issues with SSR, encountering difficulties when attempting to use third-party libraries. The best practice to solve this problem is to identify and separate app functionalities that can function only in the browser environment. By checking if the window object is defined, you can prevent these client-specific scripts from running during the server-side rendering process.

To illustrate, let's consider a tricky situation where you're using a third-party library that interacts with the window object:

import thirdPartyLibrary from 'third-party-library';

function myComponent(){
    // The following line will throw an error during SSR

To avoid this error during SSR, a common practice is to guard the usage of browser-specific APIs:

import thirdPartyLibrary from 'third-party-library';

function myComponent(){
    // The following code will not run during SSR
    if (typeof window !== 'undefined') {

In this real-world example, typeof window !== 'undefined' checks if the code is running in the browser environment or on the server. If it's in the browser, it runs the third-party library code, allowing you to avoid errors during server-side rendering. Following best practices like these will help avoid common pitfalls associated with SSR and ensure seamless user experiences.


In this comprehensive article about server-side rendering (SSR) in JavaScript, the author explores the critical roles and benefits of SSR in modern web development. They discuss the process of SSR, its strengths and limitations, and compare it with client-side rendering. The article also provides proven strategies and best practices for avoiding common pitfalls in implementing SSR. The key takeaway is the importance of carefully considering the specific requirements of a web application when deciding whether to implement server-side rendering. As a challenging task, the reader is encouraged to explore how they can leverage the strengths of both SSR and client-side rendering through a hybrid rendering strategy to optimize performance and user experience.

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