JavaScript SEO

How Google handles a JavaScript page

Google processes JS-heavy pages in three steps: it crawls the URL, queues the page for rendering, then indexes what the render produces. Every page that returns a 200 status goes to the render queue whether or not it uses JavaScript. When resources free up, Google’s Web Rendering Service runs a headless, evergreen Chromium build (the same engine as Chrome) to execute the scripts. That queue is the catch. A page “may stay on this queue for a few seconds, but it can take longer than that.” Until the render happens, content injected by JavaScript is invisible to the index. Google states the rule plainly: “If the content isn’t visible in the rendered HTML, Google won’t be able to index it.”

Common ways JS breaks indexing: routing with URL fragments (#) instead of real paths, single-page apps that return 200 on missing routes (soft 404s), canonical tags injected by script, and lazy-loaded content that never triggers for a crawler. Google’s standing advice is that server-side or pre-rendering “is still a great idea,” because it is faster for users and not every bot runs JavaScript. Dynamic rendering, the old serve-HTML-to-bots trick, is now labeled “a workaround and not a long-term solution”; Google points sites toward server-side rendering, static rendering, and hydration instead.