Rendering

Rendering is the process of executing a page's JavaScript to produce the final HTML content, which search engines must do before they can read JS-dependent content.

Google can render JavaScript, but it happens as a separate, delayed second wave after initial crawling — content that only appears after JS execution can take substantially longer to get indexed than content present in the initial HTML, and rendering can fail entirely for complex or resource-heavy scripts. This is the core reason server-side rendering and static generation remain preferred for SEO-critical pages over pure client-side rendering.

The practical test: view a page's source via "fetch as Google" or the URL Inspection tool's rendered HTML, not just the browser's rendered DOM — if critical content (titles, body copy, links) is missing from what the crawler actually processed, that content may be invisible to indexing regardless of how it looks in a normal browser.