Free HTTP Header Checker

Security headers are invisible SEO and trust infrastructure — but browsers won't let a web page read another site's headers. NToolHub's HTTP Header Checker is honest about that: you get precise curl commands for full header dumps plus one-click graded scans from SecurityHeaders.com and Mozilla Observatory.

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Why no live result here? Reading another site’s response headers from a web page is blocked by CORS — servers only expose headers to origins they explicitly allow. Instead, this tool builds the exact commands and one-click lookup links you need — everything runs from your own terminal or trusted lookup services.
Private by design. This page performs no live network lookups and uploads nothing — it only generates commands and links that run on your own machine or on trusted lookup sites you open yourself.

How to Use the HTTP Header Checker

  1. Paste the URL whose headers you want to inspect.
  2. Click Get Header Commands for copy-ready curl commands.
  3. Run them in your terminal to see the raw response headers.
  4. Or launch a SecurityHeaders.com scan for a graded security report.

Features

Enter any URL to generate curl -I, redirect-following header-filter and verbose commands, plus direct links launching SecurityHeaders.com and Mozilla Observatory scans — with a checklist of the key headers to look for.

Benefits & Use Cases

You see the real response headers — HSTS, CSP, framing and caching policy — instead of a simulated guess, and the graded scans turn findings into a prioritized hardening roadmap.

Tips

Prioritize strict-transport-security, content-security-policy and referrer-policy; verify security headers on the final URL after redirects; and re-scan after every deployment.

Frequently Asked Questions

Why can't this page fetch headers directly?

Reading another site's response headers from JavaScript is blocked by CORS unless that server explicitly allows it — which virtually none do. Curl and dedicated scanners are the real tools.

Which security headers matter most?

Strict-Transport-Security (HTTPS enforcement), Content-Security-Policy (XSS defense), X-Frame-Options (clickjacking), and Referrer-Policy (privacy).

Do security headers affect SEO?

Indirectly: HTTPS/HSTS is a confirmed signal, and compromised or browser-flagged sites lose traffic fast. Security is foundational, not optional.

What's the difference between the two scanners?

SecurityHeaders.com grades header presence quickly; Mozilla Observatory adds TLS, CSP analysis and broader best-practice checks for a deeper audit.

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