HTTP headers lookup

What HTTP response headers are

When a browser requests a webpage, the server returns a set of HTTP headers along with the content. These headers communicate metadata about the response: the content type, caching directives, security policies, server software, cookies, redirects, and more. Inspecting them is an essential diagnostic step for understanding how a server behaves.

Headers you may see

• Content-Type declares the media type and character encoding of the response.
• Cache-Control and Expires control how long browsers and intermediaries may cache the response.
• Content-Encoding indicates compression such as gzip or Brotli.
• Strict-Transport-Security enforces HTTPS and defines HSTS policy.
• Content-Security-Policy restricts which sources can load resources.
• X-Frame-Options and Referrer-Policy control framing and referrer behavior.
• Set-Cookie transmits cookies to the client.
• Location is used in redirect responses to specify the target URL.

Practical applications

Header inspection helps verify caching behavior, confirm that compression is enabled, check security policy implementation, and debug redirect chains. It is also useful when diagnosing mixed-content issues, cookie problems, or unexpected content types. Developers and site administrators use headers to validate server configuration after changes and to compare behavior between environments.

Limitations

This tool makes a single GET request and displays the headers returned for that response. Headers can vary by request method, path, cookies, user agent, and server configuration. Some headers are added or modified by CDNs and proxies. The tool does not follow redirects automatically or explain whether each header is optimally configured. Use it to observe actual server responses and combine it with configuration knowledge when making decisions.