JavaScript, Software Development

React.js Render Modes

by Walter S.

Rendering is an essential aspect of any web application. For apps developed using the React.js library, multiple rendering methods can be applied, each offering unique benefits and drawbacks. React developers often find themselves contemplating which render mode to choose to optimize their application’s performance. The aim of this article is to shed light on React’s render modes, their pros and cons, and advice on when to use one over the other.

Render Modes in React

React.js supports several render modes, but we will focus on the three main ones:

  1. Client-Side Rendering (CSR)
  2. Server-Side Rendering (SSR)
  3. Static Site Generation (SSG)

1. Client-Side Rendering (CSR)

CSR is the standard rendering mode in React, where the rendering happens in the user’s browser. The browser downloads the JavaScript bundle and executes it to generate the HTML content.

Pros:

  • Interactive content: Since rendering happens at the client-side, it supports interactive and dynamic content without any server request.
  • Reduced server load: Since the server only needs to send the JavaScript file, it can handle more requests, reducing the server’s load.

Cons:

  • Delayed initial load: It can cause a delay in the initial page load as the entire JavaScript bundle needs to be downloaded and executed before the user sees anything other than a loading screen.
  • SEO implications: Many search engine crawlers do not execute JavaScript or do so less effectively than HTML, potentially negatively impacting the site’s SEO.

When to use CSR?

CSR is best suited for web applications that are highly interactive, have less concern for SEO, or rely on modern search engine capabilities to index JavaScript content.

2. Server-Side Rendering (SSR)

In SSR, the server generates the HTML for a page on each request. The client then receives a fully rendered page, reducing the time to first meaningful paint (TTMP).

Pros:

  • Faster initial load: SSR sends a fully rendered page to the client, allowing the user to see the page faster than in CSR.
  • Better for SEO: As the page is fully rendered when it arrives at the client, it’s easier for search engine crawlers to scan and index the page, which is beneficial for SEO.

Cons:

  • Server load: Each request results in a full-page render, which can strain the server resources, especially during high traffic periods.
  • Delayed interactivity: While the initial content load is quicker, full interactivity may be delayed as the client still needs to download and parse the JavaScript bundle.

When to use SSR?

SSR is best for public-facing web pages where SEO is crucial and the user needs to see the content immediately, such as blogs, marketing sites, or news articles.

3. Static Site Generation (SSG)

SSG pre-renders pages at build time, creating static HTML pages. These pages can then be served from a Content Delivery Network (CDN).

Pros:

  • High performance: Since pages are served as static HTML, they can be loaded extremely quickly, resulting in a better user experience.
  • Better SEO: Similar to SSR, SSG offers full pre-rendered HTML for search engine crawlers to index, improving SEO.
  • Low server load: Static pages can be served directly from a CDN, reducing the load on your server.

Cons:

  • Limited dynamic content: Dynamic changes are harder to manage as the entire site needs to be re-rendered and redeployed for any changes.
  • Build time: Larger sites with many pages can have longer build times.

When to use SSG?

SSG is optimal for sites where the content does not change frequently, such as blogs, documentation sites, or marketing sites.

Conclusion

Choosing the right render mode can greatly influence an application’s performance and the user’s experience. While CSR is suitable for dynamic and interactive apps, SSR and SSG offer enhanced SEO and faster initial load times. SSR is best suited for SEO-critical pages needing instant rendering, while SSG shines when serving static content with infrequent updates.

Always keep your app’s unique needs and trade-offs in mind while choosing the rendering mode. Remember that these modes can also be combined, enabling you to leverage the benefits of each according to different scenarios in your application. This combination approach is often referred to as hybrid rendering or Incremental Static Regeneration (ISR) in Next.js, a React framework that supports all three render modes.

With React’s flexibility and these rendering options, developers can tailor their applications to offer the best user experience, improve SEO, and manage server resources effectively.