HTTP response headers are metadata sent by a web server alongside the page content. They tell the browser how to handle the response — whether to cache it, what content type it is, which security policies apply, and more. Headers like Content-Security-Policy, Strict-Transport-Security, and X-Frame-Options are critical for web security.
Checking headers helps you diagnose caching issues, verify CORS configuration, confirm HTTPS redirects, inspect server software versions, and audit security headers. Security-conscious developers use this to ensure their sites send the recommended security headers like HSTS, CSP, and X-Content-Type-Options.
Browsers enforce CORS restrictions that prevent JavaScript from reading response headers of cross-origin requests directly. This tool routes the request through our server, which fetches the headers on your behalf and returns them as JSON — giving you full visibility into all response headers without any CORS limitations.