With SSR, the server runs your JavaScript framework (React, Vue, Svelte, etc.), generates complete HTML, and sends that to the browser. The visitor sees rendered content immediately — headlines, images, text — while JavaScript loads in the background to make the page interactive. Compare this with client-side rendering (CSR), where the server sends an empty HTML shell and the browser has to download, parse, and execute JavaScript before showing anything.
For landing pages, the difference is brutal. A CSR React app might show a blank white screen for 2-4 seconds on a mid-range phone while JavaScript bundles download and execute. That's 2-4 seconds of your paid traffic staring at nothing. SSR pages show content within the TTFB + HTML download time — typically under 1 second. Your headline is readable before a CSR page even starts rendering.
SSR, SSG, or ISR?
For most landing pages, Static Site Generation (SSG) is even better than SSR. SSG pre-builds the HTML at deploy time, so there's no server computation per request — it's just serving a static file from a CDN. Use SSG for pages that don't change per-visitor. Use SSR when you need personalization (different content based on user, location, or A/B test variant). ISR (Incremental Static Regeneration) gives you the best of both — static speed with periodic updates.
The SEO benefit is equally important: search engine crawlers can reliably index SSR/SSG content without executing JavaScript. CSR pages depend on Google's rendering queue, which can delay indexing by days or weeks and sometimes fails entirely for complex SPAs.