What's this website built with?

It fetches the page once and looks for fingerprints that technologies leave behind: headers like x-vercel-id or cf-ray, cookies, the generator tag, script and stylesheet URLs, and telltale markup like __NEXT_DATA__. Every result shows the evidence it found.

Some technologies leave no trace in the first HTML — for example tools that load only after you click, or sites that render entirely in the browser. Backend languages and databases are usually hidden on purpose.

A quick check of seven protections browsers support: HTTPS, Strict-Transport-Security, Content-Security-Policy, clickjacking protection, X-Content-Type-Options, Referrer-Policy and Permissions-Policy. 6–7 passing is an A, fewer than 3 is an F.

You can check up to 8 sites a minute (and 150 a day). Results are cached for a few hours, so re-checking the same site is instant.