CrawlCheck — second vantage

Measures what AI and search crawlers are served from your site, from your browser — including what only exists after JavaScript.

A server can tell you what a crawler is served from a data centre. It cannot tell you what one is served from your address, in your browser, after your JavaScript has run. CrawlCheck measures the half a server is structurally blind to. - Identity probe — requests the page as each named AI crawler and as your own browser, and shows where the answers differ. A refusal that your browser never sees is the finding. - Render delta — what only exists after JavaScript. Headings, prices, schema and links that are on your screen and absent from the delivered HTML. - Field vitals — LCP, CLS, TTFB and long tasks from this page load, on this connection. No API key, and it works on sites too small for public field data. - Consent and session delta — the wall served to an anonymous client that you never see, because your session is already past it. - Machine files — whether robots.txt, llms.txt, agents.md and the sitemap resolve, and whether a 200 actually contains the file rather than a verification page. Nothing is uploaded. Measurements stay in your browser. Requests are made without your cookies. The extension identifies itself honestly and does not impersonate any crawler to gain access it would not otherwise have. Free. A CrawlCheck licence adds the scored report and weekly monitoring at crawlcheck.io, and the extension works fully without one.