Free HTTP Header Checker — View Request & Response Headers Online
Inspect HTTP request and response headers for any URL. View your browser's request headers, check security headers (CSP, HSTS, X-Frame-Options), debug API responses, and analyze server configurations. Our free HTTP header viewer works instantly with no installation required.
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HTTP Header Viewer
Enter a URL to inspect its response headers. Your browser's request headers are shown below.
Loading your request headers…
See what your browser sends
Fetch and inspect any URL's headers
Check CSP, HSTS, X-Frame-Options
Debug API responses and caching
What Are HTTP Headers and Why Do They Matter?
HTTP headers are key-value pairs sent with every HTTP request and response. They carry essential metadata that controls how browsers and servers communicate. Request headers tell the server about your browser, language preferences, accepted content types, cookies, and compression support. Response headers tell your browser about caching rules, content type, security policies, server identity, and more.
Understanding HTTP headers is crucial for web developers, security professionals, and system administrators. Headers control everything from how pages are cached (Cache-Control, ETag) to how they're secured (Content-Security-Policy, Strict-Transport-Security) to how they handle cross-origin requests (Access-Control-Allow-Origin).
Important Security Headers to Check
Content-Security-Policy (CSP) prevents XSS attacks by controlling which resources can load. Strict-Transport-Security (HSTS) forces HTTPS connections. X-Frame-Options prevents clickjacking by controlling iframe embedding. X-Content-Type-Options prevents MIME-type sniffing. Referrer-Policy controls what information is sent in the Referer header. Missing security headers are a common vulnerability — use this tool to verify your site's headers are properly configured.
Common Use Cases for HTTP Header Checking
Developers inspect headers to debug API calls and verify caching behavior. Security researchers check for missing security headers and misconfigurations. DevOps engineers verify CDN and load balancer configurations. SEO professionals check redirect headers and canonical URLs. When troubleshooting why a page isn't loading correctly, checking headers often reveals issues with caching, CORS policies, or content negotiation.
Limitations of Browser-Based Header Checking
When you enter a URL in our tool, the request is made from your browser. Many sites block cross-origin requests (CORS), so you may only see limited headers or encounter errors for sites that don't allow cross-origin access. The browser request headers section shows what your browser sends to our test endpoint, giving you visibility into your user agent, language preferences, and other request metadata.
For IP and network details, use our IP address lookup. For domain DNS records, try DNS lookup. To check your VPN status, use VPN detection. See also What is my IP, ping test, traceroute, and port checker.
Privacy, Accuracy & Security
Privacy: We don’t store the URLs you check. Accuracy: Headers are fetched from your browser; CORS may limit results for some sites. Security: HTTPS only. Free, no signup.
Frequently Asked Questions About HTTP Headers
What are the most important HTTP headers?
For security: Content-Security-Policy, Strict-Transport-Security, X-Frame-Options. For performance: Cache-Control, ETag, Content-Encoding. For functionality: Content-Type, Authorization, Set-Cookie. For CORS: Access-Control-Allow-Origin.
Why can't I see headers for some URLs?
Many websites block cross-origin requests (CORS). When you fetch a URL from our tool, the request comes from your browser, and the target server may reject cross-origin requests. You'll see full headers for URLs that have CORS enabled.
How do I check if my security headers are set correctly?
Enter your website URL in the tool above and check the response headers. Look for Content-Security-Policy, Strict-Transport-Security, X-Frame-Options, X-Content-Type-Options, and Referrer-Policy. Missing any of these indicates a potential security gap.
Is this HTTP header checker free?
Yes, our HTTP header viewer is completely free with no signup or installation required.