JavaScript SEO Analyzer

It fetches your URL twice: once as a plain HTML request (what crawlers see without rendering JavaScript) and once through a real headless Chrome browser (what users and modern search engines see after JS executes). It then counts every heading, paragraph, link, image, meta tag, and link tag in both versions and reports the difference.

Google's main crawler indexes a page in two waves: an initial pass on the raw HTML and a deferred render pass. ChatGPT, Perplexity, Bing, and most other AI / search bots only do the first pass — they never render JavaScript. Anything that lives only in the rendered DOM (headings, copy, links, canonical tags, hreflang, JSON-LD schema) is invisible to those bots, which means it doesn't help you rank or get cited.

Any element present in the rendered DOM but missing from the raw HTML response. The tool reports per-element-type deltas (e.g. "1 of 3 H2s injected by JavaScript", "12% of body words injected by JavaScript") so you can see exactly what crawlers are missing.

Not necessarily. Modals, lazy-loaded comments, and interactive widgets are fine to render with JS. The risk is when primary content — H1s, body copy, internal links, the canonical tag, or hreflang alternates — only exists post-render. That's the case where you'll lose visibility in non-rendering crawlers and AI engines.

Yes. The tool extracts and compares the actual values of `<title>`, `<meta description>`, `<link rel="canonical">`, all `<link hreflang>` alternates, the full Open Graph block, and Twitter card tags — in both the raw and rendered HTML. If any of these are JS-injected or rewritten by JS at runtime, the diff will show it.

Pages built on React / Next.js / Nuxt / Gatsby / Vue without server-side rendering ship a near-empty HTML shell and inject the entire page on the client. We flag this as "SPA" when the raw HTML has fewer than 5 structural elements and under 50 visible words. "JS-heavy" means at least 60% of the visible content is added after page load.