Frontend Dogma

SSR vs. SSG vs. CSR vs. ISR—Rendering Performances Compared

by @designerly.bsky.social on , tagged , , , , , (share on Mastodon or on Bluesky)

Choosing a rendering strategy is one of the most impactful decisions you can make in frontend development. Using a suboptimal method for your goals can limit performance, leading to poor user experience and declining search engine rankings. Conversely, a favorable rendering technique can save you time and money while maximizing your site’s results.

Given the weight of this decision, understanding each method’s pros, cons, and appropriate uses is essential. Here’s a closer look at the four leading rendering strategies to help you in this endeavor.

Server-Side Rendering

SSR, once the standard for web development, renders all elements on the server before delivering content to the user. As a result, it enables fast load times, especially when users’ connections are slow or their hardware lacks power.

These fast speeds are vital for user retention, particularly for business-focused sites, as more than 80% of customers say their experience with a company is just as important as its actual products. SSR also improves search engine optimization by making pages easier to index.

The primary drawback of SSR is that it places high strain on the server. Because pages are rendered on the server for each request, high traffic or inefficient code can strain server resources, leading to slower response times or, in extreme cases, service interruptions. It also involves higher costs and complexity in development and can be slow to load interactive elements, even if the rest of the page loads quickly.

Given these pros and cons, SSR is a good choice when:

Static Site Generation

SSG takes things a step further. In this method, you generate and pre-render the entire site in HTML at build time, long before any request. Consequently, its load times are almost instantaneous, which is great for UX and SEO.

SSG is ideal for bandwidth-hungry images and videos. This can be a useful marketing tool, especially in light of SSG’s SEO benefits. However, SSG doesn’t support real-time data and updates take a long time, especially for larger sites.

These unique characteristics make SSG best for:

Client-Side Rendering

As JavaScript became the most-used programming language, CSR grew into the unofficial frontend development standard. As the name implies, this method renders content on the client’s side through JavaScript, reducing coding complexities for developers and minimizing server loads.

Recently, CSR has begun to fall out of favor with some devs. This decline stems mostly from the technique’s long load times and slower user experiences, which are not ideal for SEO.

Still, CSR is useful for:

Incremental Static Regeneration

While less common, ISR deserves attention, too. It largely works the same as SSG, generating entire sites at build time, but it regularly regenerates some pages to update their content. Consequently, you get the SEO benefits of SSG without the downside of slow updates.

As beneficial as ISR can be, it’s also complex. With IT skills shortages anticipated to affect over 90% of organizations by 2026, organizations must prepare to tackle these difficulties. ISR also produces a lag between fetching new data and updating a page.

In light of these benefits and disadvantages, ISR is best for:

Use the Rendering Method That Works Best for You

There’s no single correct answer as to which rendering strategy performs best, as each has situations where it outshines others and circumstances where it falls short. You must recognize these unique strengths and weaknesses to use these methods effectively.

You may need to combine several techniques within the same application to meet the goals for each page or section. Regardless of what you do, an informed decision starts with learning about these strategies and experimenting to find what works for you.

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