HTTP Header Checker
Inspect response headers from any website. Check security headers, caching policies, and server configuration instantly.
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Why HTTP Headers Matter
HTTP response headers are instructions your server sends to every browser and crawler that requests a page. They control caching behavior, enforce security policies, dictate content types, and influence how search engines process your responses. Misconfigured headers can expose your site to XSS attacks, prevent efficient caching, or leak server version information to attackers. Inspecting headers regularly is a fundamental part of web security and performance hygiene.
Security Headers Overview
Security headers are your first line of defense against common web attacks. They instruct browsers to enforce protections like blocking cross-site scripting, preventing clickjacking, and restricting which external resources can load. Major security headers include Content-Security-Policy, Strict-Transport-Security, X-Content-Type-Options, and X-Frame-Options. Sites missing these headers are significantly more vulnerable to injection attacks and data theft.
Common Security Headers
- Content-Security-Policy (CSP) — Controls which scripts, styles, images, and other resources a browser is allowed to load. A strong CSP prevents most XSS attacks by blocking inline scripts and unauthorized external sources.
- Strict-Transport-Security (HSTS) — Forces browsers to use HTTPS for all future requests to your domain. Once set, even if a user types http://, the browser upgrades to HTTPS before making the request, preventing SSL-stripping attacks.
- X-Content-Type-Options — When set to 'nosniff', prevents browsers from MIME-type sniffing responses. This stops attackers from disguising executable files as harmless content types.
- X-Frame-Options — Controls whether your page can be embedded in iframes on other sites. Setting it to DENY or SAMEORIGIN prevents clickjacking attacks where malicious sites overlay invisible frames on your content.