JavaScript SEO
JavaScript SEO covers the work of making content generated by JavaScript visible to search engines. Google does render JavaScript, but in a second pass that can be delayed. Other crawlers and AI systems often do not render it at all.
Why it matters for your rankings
Google crawls in two waves. First it reads the raw HTML, then it queues the page for rendering, which may happen minutes or weeks later depending on how much it wants your content.
If your main copy, internal links and metadata only exist after JavaScript runs, everything important sits behind that queue. On a large site the practical result is content that takes far longer to index, or never gets indexed at all. Other consumers are less forgiving still. Bing renders less reliably than Google, and most AI answer engines read raw HTML only, so a client-rendered site can be effectively invisible to them. Server-side rendering or static generation removes the entire class of problem.
How to check it on your site
Compare raw HTML against rendered
View source and search for your main heading and body copy. If they are missing, they exist only after rendering.
Use the URL Inspection tool
Search Console's 'View Crawled Page' shows the rendered HTML Google actually stored. Compare it against what you see in a browser.
Crawl with JavaScript disabled
Run Screaming Frog in text-only mode. Any page that loses its content or links is at risk.
Check that links are real anchors
Navigation built from onclick handlers or buttons is not crawlable. Links must be anchor tags with href attributes.