Rendering

Rendering is how a page's source becomes its visible, interactive form. The strategic question for SEO is where it happens. With server-side rendering and static rendering, the server sends fully formed HTML and a crawler reads the content immediately. With client-side rendering, the server sends a near-empty shell and the browser builds the content with JavaScript, which means a crawler that does not run JavaScript reads nothing.

Googlebot does render JavaScript, but on a deferred second pass and with caveats, so even for Google, server-rendering the important content is safer and faster to index. For the AI crawlers, server-rendering is not optional: they do not execute JavaScript in their production paths, so client-rendered content is invisible to ChatGPT, Claude, and Perplexity.

Modern frameworks give you the tools to render on the server by default and hydrate selectively. The Next.js App Router renders Server Components to HTML and only ships JavaScript for the interactive islands. The practical rule is to keep primary content in the server-rendered output and reserve client rendering for genuine interactivity. The render-parity diff is how we measure whether a site is actually following that rule.