HTTP Response Header Checker

Analyze server configurations and security protocols by inspecting raw headers.

Enter a URL and click "Fetch Headers" to analyze metadata.

What is HTTP Response Header Checker

The HTTP Response Header Checker is a web diagnostics utility designed to retrieve and inspect HTTP response headers returned by web servers. When your browser requests a web page, the hosting server attaches metadata headers containing security parameters, server configuration variables, cache policies, and connection states.

Analyzing these headers provides insight into site infrastructure and security posture. This tool makes server audits easy by querying domains via a proxy bridge to bypass CORS errors and rendering raw key-value headers alphabetically.

How to Use HTTP Response Header Checker

  1. Input domain target: Enter the target website URL (e.g., https://example.com) into the text field. The tool will automatically prepend protocol headers if omitted.
  2. Trigger header retrieval: Click the Fetch Headers button or press Enter.
  3. Examine proxy connections: Wait as the tool routes requests through a secure CORS proxy to fetch remote metadata.
  4. Read HTTP headers: Inspect the alphabetical list of headers and their corresponding values returned in the grid workspace.

Key Features

  • Alphabetical Keys Sorting: Automatically organizes returned headers alphabetically for easier auditing.
  • Bypasses CORS Restrictions: Uses CORS proxies to resolve security policies that usually block client-side header queries.
  • Responsive Grid Layout: Formats keys and values into separate panels, preventing long header values from breaking layouts.
  • Real-time Status Diagnostics: Displays active progress alerts and captures server-side response codes.

Common Use Cases

  • Web Security Auditing: Inspecting security headers like Content-Security-Policy (CSP), Strict-Transport-Security (HSTS), and X-Content-Type-Options.
  • Caching Audits: Checking server Cache-Control and Expires rules to optimize browser caching and speed up page loads.
  • Server Signature Check: Identifying server technologies (such as Nginx, Apache, or Cloudflare proxies) used by target websites.

Frequently Asked Questions

Q: What are HTTP response headers?
A: HTTP response headers are metadata pairs sent by a server alongside requested web documents. They communicate technical directives, security policies, cache times, and encoding structures to the user's browser.

Q: Why does the tool use a proxy to check headers?
A: Browsers implement Same-Origin policies that block scripts from reading HTTP headers of external websites. The proxy acts as a bridge, fetching headers server-side and returning them to your browser.

Q: What security headers should my website ideally implement?
A: A secure server should implement headers like `Content-Security-Policy` (to block script injections), `Strict-Transport-Security` (to enforce HTTPS), `X-Frame-Options` (to prevent clickjacking), and `X-Content-Type-Options` (to block MIME sniffing).

Q: Why does the Server header sometimes show "cloudflare" instead of Nginx or Apache?
A: If a website uses a reverse-proxy service like Cloudflare for security and caching, the proxy intercepts requests, replacing the host server's signature with its own.

Privacy & Data Note

Website URLs are queried in real-time through public CORS proxies. No target domains, fetched headers, or server metadata records are saved, logged, or shared by 99tool.in.