HTTP Headers Checker
Analyze HTTP response headers to check security, caching, and server info.
Security Headers We Check
- • Strict-Transport-Security: Forces HTTPS
- • Content-Security-Policy: Prevents XSS attacks
- • X-Frame-Options: Prevents clickjacking
- • X-Content-Type-Options: Prevents MIME sniffing
- • X-XSS-Protection: XSS filter
Why Check Headers?
- • Identify security vulnerabilities
- • Verify server configuration
- • Check caching policies
- • Debug API responses
- • Analyze performance settings
The security header your server is missing — and why it matters
HTTP security headers are directives sent by the server that tell browsers how to behave. Missing headers like Content-Security-Policy, X-Frame-Options, and Strict-Transport-Security leave your site vulnerable to XSS, clickjacking, and protocol downgrade attacks.
Your server got a 40% security score. That doesn't mean you were hacked — it means your HTTP response is missing headers that modern browsers rely on to enforce security policies. CSP blocks unauthorized script execution. HSTS tells browsers to always use HTTPS. X-Frame-Options prevents your pages from being embedded in iframes for clickjacking. Each header you add closes a specific attack surface.
HTTP headers as a debugging tool — caching, CORS, and API issues
When users see stale content after a deploy, or an API client rejects a cross-origin request, the root cause is almost always in the HTTP headers. Cache-Control, Vary, and Access-Control-Allow-Origin headers control exactly those behaviors.
A Cache-Control: max-age=86400 header means browsers will serve cached content for 24 hours — even after you deployed a fix. CORS errors from a missing Access-Control-Allow-Origin header look like network failures in the client but are actually server configuration issues. Checking headers directly tells you exactly what the server is sending, not what you think it's configured to send.
What a low HTTP security score actually tells you to fix
An HTTP security score is a percentage of critical security headers that are present and correctly configured. A score below 60% means multiple headers are missing that protect users from XSS, clickjacking, and protocol downgrade attacks.
Start with the headers that have the highest impact: HSTS forces HTTPS on repeat visits and prevents SSL-strip attacks. Content-Security-Policy restricts which scripts and resources can execute on your page. X-Frame-Options or the frame-ancestors CSP directive prevents your login page from being embedded in a malicious iframe. Add these three and your score will jump significantly.
Checking Set-Cookie headers to spot insecure session configuration
A Set-Cookie header without the Secure and HttpOnly flags means session tokens are accessible to JavaScript and transmittable over HTTP — both are security risks in production.
If your application uses cookies for authentication, the response headers reveal exactly how they're configured. Missing Secure flag means cookies are sent over HTTP. Missing HttpOnly flag means JavaScript can read the cookie — making XSS attacks immediately dangerous. SameSite=Lax or Strict prevents cross-site request forgery. These are not abstract recommendations — they're header values your server sets per response.