Verify whether a crawler-facing page's raw HTML differs materially from its client-rendered DOM, and fix gaps that hide content from bots

Steps

1. Fetch the page with a plain HTTP client (no JS execution) and capture the raw HTML as delivered to a non-rendering crawler
2. Separately render the same URL with a headless browser (or via the URL Inspection API's 'View Tested Page' rendered HTML/screenshot) to capture the post-JavaScript DOM
3. Diff the two HTML snapshots for critical SEO elements: title, meta description, canonical tag, headings, body copy, and internal links
4. Confirm content that only appears after client-side rendering (e.g. lazy-loaded product data, infinite scroll) is present in the rendered snapshot Google actually indexes from
5. Check that render-blocking resources (JS/CSS Google needs to render the page) are not disallowed in robots.txt, which would prevent Googlebot from producing the rendered version at all
6. Re-run the diff after any front-end framework upgrade or hydration change, since rendering behavior can regress silently