Enter a URL and see its full redirect chain, response headers and a checklist of security headers: HSTS, CSP, X-Frame-Options and friends.
HSTS forces HTTPS, CSP restricts where scripts load from, X-Frame-Options blocks clickjacking — the top three to start with.
Extra hops slow the page down and can leak URL parameters; ideally one redirect at most.
Some servers vary answers by user agent, cookies or region — the tool requests from its own server without your cookies.