Client-side rendering (CSR) and Server-side rendering (SSR)

Client-side rendering (CSR) and Server-side rendering (SSR) are two approaches used to display content on web pages, and they differ in how and where the rendering of HTML content occurs.

1. Client-Side Rendering (CSR)

In client-side rendering, the browser (client) downloads a minimal HTML page along with JavaScript files. The content of the page is rendered dynamically by JavaScript running in the browser after the initial page load. Modern frameworks like React, Angular, and Vue commonly use CSR.

• How it works:

  • When a user visits a website, the browser initially receives a basic HTML shell.

  • The JavaScript files are then loaded and executed, which dynamically fetches the content and updates the DOM (Document Object Model) to display the full page.

  • The rendering happens on the client’s machine (browser).

• Advantages:

  • Interactive and dynamic UIs: CSR enables the creation of highly dynamic and responsive user interfaces.

  • Fast subsequent interactions: After the initial page load, navigating through the site is often faster since only the necessary data is fetched, without needing to reload the entire page.

• Disadvantages:

  • Slower initial load: The initial page load can be slower since the browser needs to download and execute JavaScript before rendering the content.

  • SEO challenges: Because search engines may have difficulty indexing dynamically rendered content, SEO can be a concern.

2. Server-Side Rendering (SSR)

In server-side rendering, the HTML is generated on the server for each request, and a fully-rendered page is sent to the browser. The browser displays the content immediately without waiting for JavaScript to execute.

• How it works:

  • When a user requests a page, the server processes the request, fetches the necessary data, and generates the HTML content on the server-side.

  • The fully rendered HTML page is then sent to the client’s browser, where it is immediately displayed.

  • JavaScript can still be used to make the page interactive after the initial load.

• Advantages:

  • Faster initial load: The user can see the page content immediately because the server sends fully-rendered HTML.

  • Better SEO: Since the content is present in the HTML sent to the browser, search engines can easily index the page content.

• Disadvantages:

  • More server load: Since the server has to generate a fully-rendered page for every request, it can increase the load on the server.

  • Slower interactions: Subsequent interactions like navigation can be slower because new HTML has to be requested from the server.

Comparison:

When to Use CSR or SSR:

• Use CSR when building highly dynamic, single-page applications (SPAs) where user interactivity is key and SEO is less of a concern.

• Use SSR when SEO is important, or if you want to improve the performance of the initial page load, such as for blogs, e-commerce sites, or static websites. Some frameworks like Next.js allow hybrid approaches (combining CSR and SSR).