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Security Headers Overview (Security Headers)

Security Glossary - Web Security

Definition: Security headers are HTTP response headers that instruct browsers to enable security features, restrict dangerous behaviors, and protect against common web attacks. Key security headers include Content-Security-Policy (CSP), Strict-Transport-Security (HSTS), X-Frame-Options, X-Content-Type-Options, Referrer-Policy, and Permissions-Policy.

Why You Should Care About Security Headers

Security headers are one of the most effective and cost-efficient security improvements you can make. They are server configuration changes that require no code modifications and protect every page on your site. A well-configured set of security headers defends against XSS, clickjacking, MIME sniffing, protocol downgrade attacks, and information leakage.

Many websites have no security headers at all, leaving them vulnerable to common attacks that headers are specifically designed to prevent. Adding even the basic headers (HSTS, X-Frame-Options, X-Content-Type-Options) significantly improves security posture.

The recommended baseline security headers are: Strict-Transport-Security (force HTTPS), Content-Security-Policy (prevent XSS), X-Frame-Options: DENY (prevent clickjacking), X-Content-Type-Options: nosniff (prevent MIME sniffing), Referrer-Policy: strict-origin-when-cross-origin (limit referrer leakage), and Permissions-Policy (restrict browser APIs).

How to Verify

A security audit scans all security headers on your site and grades their configuration. It identifies missing headers, misconfigured values, and opportunities for improvement. Run an audit after any server configuration change.

Run a Security Audit

Questions and Answers

Which security headers should I add first?
Start with: X-Content-Type-Options: nosniff, X-Frame-Options: DENY, and Strict-Transport-Security. These are simple, low-risk additions. Then add Referrer-Policy and Permissions-Policy. Content-Security-Policy should be last because it requires the most careful configuration.
Can security headers break my website?
Most headers (X-Content-Type-Options, X-Frame-Options, Referrer-Policy) have no impact on functionality. HSTS and CSP can cause issues if misconfigured. Test HSTS with a short max-age first, and use CSP in report-only mode before enforcing.

Learn More

HTTP Strict Transport Security Content Security Policy X-Frame-Options X-Content-Type-Options Referrer-Policy
Disclaimer: DomainOptic provides automated informational scans only. Results do not constitute professional security advice, compliance certification, or a guarantee of security. Always verify findings independently.