[Next.js] SSR vs. CSR vs. SSG: Understanding Web Rendering Techniques

In crafting web applications, one of the paramount considerations is the delivery of content to the user. There are multiple methodologies for rendering a webpage, each with its unique strengths and weaknesses. This article delves deep into three primary rendering techniques: SSR (Server Side Rendering), CSR (Client Side Rendering), and SSG (Static Site Generation). The intent is to elucidate when and why each method is utilized, shedding light on their respective advantages and pitfalls in a manner that even novices can comprehend.

Understanding Server Side Rendering (SSR)

SSR (Server Side Rendering) refers to the methodology where web pages are rendered directly on the server.

When a user requests access to a web page, the server comprehensively renders the content of that page and sends the fully-formed HTML page to the user's browser. Consequently, the browser can instantly display the page without the need for additional JavaScript execution.

How SSR Works

1. Request: When a user initiates access to a webpage, this request is relayed to the server.
2. Data Retrieval: The server procures the requisite data for the webpage from databases or APIs.
3. Rendering: Leveraging the acquired data, the server fully renders the webpage.
4. Response: The server then transmits the rendered webpage to the user.
5. Display: The user's browser presents the fully rendered webpage as received from the server.

SSR Example Using Next.js

Next.js offers tools that simplify the implementation of SSR. Here’s a rudimentary illustration of a webpage leveraging SSR through Next.js:

1. Crafting the Data Retrieval Function: Start by composing a function on the server to retrieve data. For this illustration, we'll utilize a function that returns arbitrary data.

function fetchData() {
  return {
    title: "SSR with Next.js",
    content: "Understanding Server Side Rendering via Next.js"
  };
}

2. Page Rendering in Next.js: Next.js incorporates the getServerSideProps function, allowing the server to retrieve data and subsequently pass it to the page component.

export async function getServerSideProps() {
  const data = fetchData();
  return {
    props: { data }
  };
}

function HomePage({ data }) {
  return (
    <div>
      <h1>{data.title}</h1>
      <p>{data.content}</p>
    </div>
  );
}

export default HomePage;

In the above exemplar, getServerSideProps exclusively executes on the server. The data fetched via this function is relayed to the HomePage component, enabling users to instantaneously view the rendered outcome of the HomePage component.

Embracing Next.js allows for the streamlined application of SSR with just a few lines of code. For developers aiming to augment webpage load speeds and elevate SEO, SSR can prove to be an invaluable asset.

Pros and Cons of SSR (Server Side Rendering)

SSR, denoting the server-side rendering of web applications, offers substantial benefits in specific scenarios, yet it's not devoid of challenges. Understanding these can guide decisions on the aptness of SSR for a given project.

Advantages of SSR:

1. Accelerated Initial Page Load: Users receive a fully rendered page, replete with all requisite data, resulting in a swift initial load time - a significant enhancement to user experience (UX).
2. SEO Optimization: Search engine crawlers can effortlessly discern and index the content of pages rendered server-side, even in environments where JavaScript isn't operational, thus boosting SEO efficacy.
3. Efficacious Caching: With SSR, once a page is rendered, it can be cached. For subsequent identical requests, the cached data can be swiftly deployed, reducing server strain and presenting users with faster page load times.
4. Browser Compatibility: In instances where frontend frameworks reliant on JavaScript are used, certain older browsers might not support some JS functionalities. Utilizing SSR, which presents fully rendered HTML to the client, mitigates dependencies on client-side JavaScript execution, ensuring consistent page displays even on legacy browsers.

Disadvantages of SSR:

1. Server Strain: Each user necessitates individual page rendering, introducing additional server load, which might surge exponentially with voluminous traffic.
2. Elevated Development Intricacy: Interactions between the client and server can grow in complexity, potentially complicating both development and debugging processes.
3. TTFB (Time to First Byte) Delays: The time taken for server-side page rendering might marginally extend the duration before the initial data reaches the user.

Understanding Client Side Rendering (CSR)

Client Side Rendering (CSR) is an approach where the rendering of the web page is not done on the server but on the client's side, specifically the user's web browser.

When a user accesses a webpage, the server doesn't supply the full HTML structure but merely sends the JavaScript files. The browser then executes this JavaScript, fetching necessary data through API calls, and constructs the web page.

How CSR Works

1. Request: When the user accesses a web page, the initial HTML is largely empty. Instead, it contains essential JavaScript and CSS.
2. Download: The user's browser downloads the required JavaScript files and CSS.
3. Rendering: Once the JavaScript is downloaded and executed, it retrieves necessary data from APIs or other external sources. The web page is then constructed client-side based on this data.
4. Display: Once the data reaches the browser, the content rendered is displayed on the screen.

While this approach might result in a slightly longer initial loading time, it ensures smoother user experience since only the changed parts are updated, rather than reloading the entire page.

Is Next.js Essential for CSR?

While React.js alone is sufficient for implementing CSR, employing Next.js offers several significant advantages over using just React.js. Key features and benefits of Next.js include:

1. Page-Based Routing: Next.js provides automatic routing based on file and folder structure, allowing for easy navigation between pages without additional router configuration.
2. Built-in Optimization: Next.js comes equipped with automatic code splitting, optimized image handling, support for global CSS and modular CSS, among other optimization features.
3. API Routes: With Next.js, one can create API routes within /pages/api, simplifying backend logic processing. This allows API requests to be handled even without a separate server.
4. Plugin and Community Support: Next.js supports a range of plugins and extensions. The large and active community means a plethora of solutions and resources are readily available.

In essence, while React.js might be sufficient for basic CSR, considering the growth, scalability, diverse rendering needs, and optimization features of a web application, utilizing Next.js offers numerous benefits.

CSR Example Using Next.js

import { useEffect, useState } from 'react';

function HomePage() {
  const [data, setData] = useState({ title: '', content: '' });

  useEffect(() => {
    async function fetchData() {
      const mockData = await new Promise(resolve => {
        setTimeout(() => {
          resolve({
            title: 'Title Rendered via CSR',
            content: 'This content is rendered using CSR.'
          });
        }, 1000);
      });
      setData(mockData);
    }

    fetchData();
  }, []);

  return (
    <div>
      <h1>{data.title}</h1>
      <p>{data.content}</p>
    </div>
  );
}

export default HomePage;

This code exemplifies data rendering in a Next.js project using the CSR approach. The useEffect and useState functions are React hooks used for component state management and lifecycle.

The fetchData function inside useEffect is executed only once when the web page is initially loaded. It fetches data asynchronously and sets it as a state, which is subsequently rendered in the component.

Pros and Cons of CSR

CSR is a methodology where all rendering tasks are conducted in the browser, making it highly effective for managing dynamic components of web applications, especially in modern-day applications like Single Page Applications (SPAs).

Advantages of CSR:

1. Quick Interactions: Post the initial load, all rendering resources are available client-side, resulting in swift user interactions, ensuring seamless page transitions and UI interactions.
2. Reduced Server Load: Since the server only needs to provide static files (JavaScript, CSS, HTML), there's a noticeable reduction in rendering load.
3. Frontend-Backend Segregation: The structure fetches data via APIs, facilitating a distinct development process for both frontend and backend. This concurrent development approach allows for the easy establishment of a component-based structure with high reusability.

Disadvantages of CSR:

1. Initial Loading Delays: Since the client must download and execute all JavaScript files, the initial page loading might be slow.
2. SEO Challenges: Traditional web crawlers that scan HTML content without executing JavaScript might struggle to recognize content rendered entirely via CSR. However, modern search engines are increasingly equipped to execute JavaScript to address this challenge.
3. Browser Load: As all rendering happens in the browser, performance might degrade on older devices or browsers.
4. Security Concerns: Code processed client-side is fully exposed to users, making it challenging to conceal vital logic or data.

In summary, while CSR can be highly effective for certain web applications, it's crucial to ensure its compatibility with the specific requirements of the application before implementation.

Understanding SSG (Static Site Generation)

Static Site Generation (SSG) refers to the approach where all web pages are pre-generated as static files.

Once created, these web pages consistently deliver the same files to the customer upon each server request. This method is particularly suited for websites, such as blogs, marketing sites, or documentation platforms, where the content doesn't change frequently.

How SSG Works

1. Build Time: At the point when a developer builds the website, all web pages are pre-generated as static files. During this process, necessary data is fetched from external sources (e.g., databases, APIs) and integrated.
2. Request: When a user requests access to a web page, this request is relayed to the server or a Content Delivery Network (CDN).
3. Response: The pre-generated static file is immediately served to the user without the need for additional rendering or data retrieval.
4. Display: The user's browser presents the static file received from the server.

SSG Example Using Next.js

export async function getStaticProps() {
  const data = await fetchData(); // Function to fetch external data
  return {
    props: { data }
  };
}

function BlogPage({ data }) {
  return (
    <div>
      <h1>{data.title}</h1>
      <p>{data.content}</p>
    </div>
  );
}

export default BlogPage;

This code showcases how Next.js utilizes SSG capabilities to statically generate a blog page. The getStaticProps function runs at build time, retrieving data and using it to generate the static page.

Pros and Cons of SSG (Static Site Generation)

Advantages of SSG

1. Rapid Loading Time: Since pre-generated static files are served, there's no server processing delay, allowing for content delivery at a global scale through CDNs.
2. SEO Benefits: Pre-rendered static pages are recognized efficiently by web crawlers, offering advantages for search engine optimization.
3. Reduced Server Costs: The absence of dynamic processing reduces server strain, potentially decreasing hosting expenses.
4. Security: By serving only static files, vulnerabilities related to various server-side attacks are mitigated.

Disadvantages of SSG

1. Build Duration: For extensive websites, generating all pages can be time-consuming.
2. Real-time Update Limitations: Any content changes necessitate rebuilding the website, making it less ideal for applications requiring instant data updates.
3. Dynamic Processing Constraints: Features that need to operate differently per user (e.g., user account functionalities) require separate client-side logic.

SSG can be incredibly beneficial, depending on specific scenarios and requirements. Yet, it's crucial to evaluate the nature of your application and its necessary features, then choose the most appropriate rendering approach by weighing the benefits and limitations presented in this article.

Rendering plays a pivotal role in web development. Whether it's SSR, CSR, or SSG, the optimal method varies based on the environment and demands. It's imperative to understand the nature of the web platform or application you aim to develop, recognize the user's needs, and judiciously select the best approach by taking into account the pros and cons of each method discussed here.