SvelteKit Server-Side Rendering: Complete Guide to SSR, CSR, and Prerendering

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04-01-2026, 05:45 PM #1

SvelteKit offers flexible rendering strategies that let you choose between SSR, CSR, and prerendering on a per-page basis. This thread breaks down each approach with practical examples.

Understanding Rendering Modes in SvelteKit

SvelteKit supports three rendering modes:
1. Server-Side Rendering (SSR) - HTML generated on the server for each request
2. Client-Side Rendering (CSR) - HTML generated in the browser using JavaScript
3. Prerendering - HTML generated at build time as static files

Server-Side Rendering (SSR)

SSR is the default in SvelteKit. When a user requests a page, the server runs your Svelte component and sends back fully rendered HTML.

Code:

// src/routes/products/+page.server.ts

export async function load({ fetch }) {

  const response = await fetch('/api/products');

  const products = await response.json();

  return { products };

}

Code:

<!-- src/routes/products/+page.svelte -->

<script>

  export let data;

</script>

{#each data.products as product}

  <div class="card">

    <h2>{product.name}</h2>

    <p>{product.price}</p>

  </div>

{/each}

Benefits of SSR:
- Better SEO since crawlers see full HTML content
- Faster First Contentful Paint (FCP)
- Works even if JavaScript is disabled

Prerendering Static Pages

For pages that don't change often, prerendering generates static HTML at build time:

Code:

// src/routes/about/+page.ts

export const prerender = true;

You can also prerender your entire site:

Code:

// svelte.config.js

const config = {

  kit: {

    prerender: {

      entries: ['*']

    }

  }

};

Client-Side Rendering Only

For dashboard-style apps that don't need SEO:

Code:

// src/routes/dashboard/+page.ts

export const ssr = false;

Streaming with SvelteKit

SvelteKit supports streaming SSR which sends HTML progressively:

Code:

// src/routes/feed/+page.server.ts

export async function load({ fetch }) {

  return {

    quickData: await fetch('/api/quick').then(r => r.json()),

    slowData: fetch('/api/slow').then(r => r.json()) // not awaited = streamed

  };

}

Code:

<!-- +page.svelte -->

<script>

  export let data;

</script>

<h1>Feed</h1>

<p>{data.quickData.title}</p>

{#await data.slowData}

  <p>Loading more content...</p>

{:then slowContent}

  <p>{slowContent.body}</p>

{/await}

Choosing the Right Strategy

| Page Type | Recommended Mode |
|-----------|------------------|
| Marketing/Landing | Prerender |
| Blog posts | Prerender |
| Product pages | SSR |
| User dashboard | CSR |
| Search results | SSR with streaming |

Performance Tips

- Use prerendering for static content to reduce server load
- Enable streaming for pages with slow data fetches
- Use CSR only for authenticated pages that don't need SEO
- Combine modes within the same app for optimal performance

What rendering strategy are you using in your SvelteKit projects? Let us know!

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