HTTP Headers Security Checker
Analyze HTTP security headers including HSTS, CSP, X-Frame-Options, and more. Get actionable recommendations to improve your website's security posture.
What are HTTP Security Headers?
HTTP security headers are directives sent by web servers in HTTP responses that instruct browsers how to behave when handling your site's content. These headers form a critical first line of defense against common web vulnerabilities including cross-site scripting (XSS), clickjacking, code injection, and man-in-the-middle attacks.
When properly configured, security headers significantly reduce your website's attack surface without requiring changes to your application code. They work by telling browsers to enforce security policies like blocking mixed content, preventing iframe embedding, or rejecting inline JavaScript execution. Modern browsers respect these headers and provide robust protection when they're present.
Why HTTP Security Headers Matter
Security headers protect against XSS attacks, clickjacking, MIME-sniffing vulnerabilities, and downgrade attacks. They prevent malicious scripts from executing, stop your site from being embedded in iframes, and ensure connections stay encrypted. This protection is automatic once headers are configured.
Many security standards and compliance frameworks (PCI-DSS, SOC 2, ISO 27001) require proper security header implementation. GDPR and privacy regulations also encourage their use. Having strong security headers demonstrates due diligence and can be crucial for audits and certifications.
Google considers site security in ranking algorithms. Browsers display warnings for insecure sites, damaging user trust and increasing bounce rates. Strong security headers contribute to a safer web experience, improving user confidence and potentially benefiting SEO through better engagement metrics.
Security headers require minimal configuration—just adding header directives to your web server or CDN settings. No code changes needed. Once set, they protect all pages automatically. This makes them one of the highest ROI security improvements you can make.
Forces browsers to use HTTPS for all connections to your domain. Prevents protocol downgrade attacks and cookie hijacking. Example: max-age=31536000; includeSubDomains; preload
Controls which resources browsers can load, preventing XSS attacks by blocking inline scripts and unauthorized external resources. One of the most powerful security headers but requires careful configuration.
Prevents clickjacking by controlling if your site can be embedded in iframes. Use DENY or SAMEORIGIN. Essential for protecting against UI redress attacks.
Prevents MIME-sniffing attacks by forcing browsers to respect declared content types. Set to nosniff. Simple but effective defense against type confusion vulnerabilities.
Controls how much referrer information is included in requests. Protects user privacy and prevents information leakage. Recommended: strict-origin-when-cross-origin
Controls browser features and APIs your site can access. Limits potential attack surface by disabling unnecessary features like geolocation, camera, or microphone access.
Header always set X-Frame-Options "DENY"
Header always set X-Content-Type-Options "nosniff"
add_header X-Frame-Options "DENY" always;
add_header X-Content-Type-Options "nosniff" always;
Use Transform Rules or Workers to add security headers. Cloudflare also offers managed header sets in the dashboard under Security → Headers that automatically apply best practices.
headers: () => [{
source: '/:path*',
headers: [{key: 'X-Frame-Options', value: 'DENY'}]
}]
Most security headers are safe to add immediately and won't break functionality. However, Content-Security-Policy (CSP) can block resources if misconfigured. Start with report-only mode (Content-Security-Policy-Report-Only) to test without breaking your site. Headers like HSTS, X-Frame-Options, and X-Content-Type-Options are generally safe to enable directly.
A security score of 80+ (Grade A or B) indicates good security header implementation. Scores below 60 (Grade C or worse) suggest critical headers are missing. Perfect scores (A+, 95-100) require all major security headers properly configured including strict CSP policies. Most production websites should aim for at least Grade B (70-80).
CSP is the strongest defense against XSS attacks, which account for most web vulnerabilities. It works by creating an allowlist of trusted content sources, blocking inline scripts and eval(). While challenging to implement initially, CSP prevents attackers from executing malicious code even if they find an injection point. Modern sites should prioritize CSP implementation.
Security headers have negligible performance impact—they're small text directives sent once per page load. In fact, some headers like HSTS can improve performance by eliminating HTTP-to-HTTPS redirects on subsequent visits. The security benefits far outweigh any minimal overhead. Don't skip security headers for performance reasons.
Use both for maximum compatibility. X-Frame-Options has broader browser support (works in older browsers), while CSP frame-ancestors is more flexible and modern. Setting both ensures protection across all browsers: X-Frame-Options: DENY and Content-Security-Policy: frame-ancestors 'none'.
HSTS preloading adds your domain to browsers' built-in HSTS lists, ensuring HTTPS is enforced even on first visit. Submit to hstspreload.org after setting Strict-Transport-Security: max-age=31536000; includeSubDomains; preload. Warning: preloading is permanent and affects all subdomains—test thoroughly first.
Use our checker above or browser developer tools (Network tab → click request → Headers). Online tools like securityheaders.com, Mozilla Observatory, or OWASP ZAP also provide detailed analysis. Test from multiple locations and browsers. Remember headers only apply to HTTPS traffic, so ensure you're testing the HTTPS version.
Yes! CDNs like Cloudflare, Fastly, and AWS CloudFront can inject security headers at the edge, even if your origin server doesn't send them. This is the easiest implementation method. Cloudflare offers managed security headers in their dashboard. However, origin-level configuration is still recommended for defense in depth.
Browsers simply ignore unsupported headers—there's no negative impact. Older browsers may lack support for newer headers like Permissions-Policy, but they'll still process headers they understand. This graceful degradation means you should implement all relevant security headers regardless of legacy browser support.
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