Website Tools
HTTP Headers Checker
View every HTTP response header a website sends.
Enter a domain to view its full HTTP response headers.
JustChecker monitors your websites around the clock and alerts you the instant something changes.
Frequently Asked Questions
Headers describe metadata about the response - content type, caching rules, server software, cookie settings, security policies, and more - all sent alongside the actual page content but not visible in the rendered page itself.
Advertising a specific software version can make it slightly easier for an attacker to target known vulnerabilities in that exact version - many security-conscious setups deliberately suppress or genericize this header.
This tool shows every header your server sends, unfiltered; the Security Headers Checker specifically evaluates the subset of headers relevant to browser security policy (HSTS, CSP, X-Frame-Options, etc.) and scores them.
Some headers (like Date, or a caching-related ETag) are expected to change on every request by design - this doesn't indicate any instability, just normal, request-specific header behavior.
It tells the browser how to interpret the response body - as HTML, JSON, an image, plain text, etc. - an incorrect Content-Type can cause a browser to render or download content incorrectly even if the underlying data itself is fine.
Yes - caching headers (Cache-Control, Expires) directly control whether a browser can reuse a previously downloaded resource instead of re-fetching it, which can meaningfully speed up repeat visits.