HTTP Headers Checker
Inspect your browser's HTTP request headers exactly as servers see them. Check security headers, analyze response headers from any URL, and identify missing security configurations.
What are HTTP headers?
HTTP headers are key-value pairs sent between clients (browsers) and servers with every HTTP request and response. Request headers tell the server about the client — its browser, accepted languages, cookies, and authentication tokens. Response headers tell the browser how to handle the content — caching rules, content type, security policies, and CORS settings.
Why do security headers matter?
Security headers protect your web application from common attacks. Missing or misconfigured security headers are one of the most common web vulnerabilities. Key headers include:
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HTTP security headers checklist
Every production web application should implement these security headers: Content-Security-Policy (CSP) — prevents XSS by specifying allowed content sources. Strict-Transport-Security (HSTS) — forces HTTPS connections. X-Frame-Options — prevents clickjacking. X-Content-Type-Options: nosniff — prevents MIME sniffing attacks. Referrer-Policy — controls referrer information sent with requests.
Missing or misconfigured security headers are consistently among the top web vulnerabilities. Use this HTTP headers checker to verify your security header configuration and identify gaps before attackers do.
What is CORS and how do CORS headers work?
CORS (Cross-Origin Resource Sharing) headers control which external domains can make requests to your API or web service from a browser. The key headers are: Access-Control-Allow-Origin (which domains can access the resource), Access-Control-Allow-Methods (which HTTP methods are allowed), and Access-Control-Allow-Headers (which request headers are permitted).
CORS errors are one of the most common issues when building frontend applications that connect to APIs. This tool shows the exact CORS headers returned by any URL, helping you diagnose cross-origin issues without needing to write test code.