See every HTTP response header a server sends back for a URL.
Headers are retrieved through a CORS-enabled relay, since browsers block JavaScript from reading full cross-origin response headers directly.
HTTP Header Checker fetches and displays every response header a web server sends back for a given URL, along with its HTTP status code. Headers carry a surprising amount of operationally important detail — caching rules, server software, security policies, content type — that never appears in the rendered page itself.
Because browser security policy (CORS) restricts JavaScript from reading the full set of response headers for a cross-origin request unless the server explicitly opts in, this tool routes the request through a transparent relay that performs the fetch and returns the headers as structured data. The relay does not modify the request or store the target URL; it exists purely to surface information your browser would otherwise be blocked from reading directly.
Content-Type tells you what kind of content is being served and its character encoding. Cache-Control and Expires govern how browsers and CDNs cache the response. Server and X-Powered-By can reveal the underlying web server or framework (though many sites deliberately hide or fake these for security). Security-relevant headers like Strict-Transport-Security, Content-Security-Policy, and X-Frame-Options indicate whether the site is protecting against common attack classes like clickjacking, protocol downgrade, and injection. Set-Cookie shows what cookies the server is trying to set on first response.
Developers use header checks to debug caching problems where updated content isn't showing for users. Security reviewers use them to quickly audit whether basic protective headers (HSTS, CSP, X-Content-Type-Options) are present. SEOs check for correct Content-Type and canonical-related headers when diagnosing indexing issues. Anyone integrating with a third-party API can use it to confirm rate-limit headers or authentication challenge headers being returned.
Some servers and CDNs are configured to strip non-essential headers for security or minimal-footprint reasons, and the relay can only report what the origin server actually sends.
It's not automatically critical, but it does mean the site is relying on other defenses against injection-based attacks — adding a well-scoped CSP is generally considered a security best practice.
Many admins deliberately configure their server to report a generic or blank value instead of detailed version numbers, specifically to make it harder for attackers to target known vulnerabilities in a specific version.
Yes — paste the full URL of any page and its headers will be checked exactly as requested.
Only a standard read-only HTTP request is made to the URL you provide, the same as a normal page visit — no extra data is submitted.
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