HTTP Header Checker
Analyze HTTP response headers, security configuration, redirect chains, and server behavior for any URL.
What Are HTTP Headers?
HTTP headers are key-value pairs sent between your browser and a web server with every request and response. They carry essential metadata — the content type being served, caching instructions, security policies, authentication tokens, and more.
Response headers control how browsers render pages, cache resources, and enforce security. A misconfigured header can cause performance issues, security vulnerabilities, or broken functionality. That is why checking headers is a core part of web development and server administration.
Common headers include Content-Type (tells the browser what format the data is in), Cache-Control (how long to cache resources), and Set-Cookie (stores session data).
Essential Security Headers
Security headers tell browsers how to behave when handling your site's content. Missing headers leave your users vulnerable to attacks like cross-site scripting, clickjacking, and data injection.
Strict-Transport-Security (HSTS)
Tells browsers to only connect via HTTPS, even if the user types http://. Prevents SSL stripping attacks. max-age=31536000; includeSubDomains
Content-Security-Policy (CSP)
The most powerful security header. Defines approved sources for scripts, styles, images, and other resources. Blocks inline scripts and unauthorized external content, making XSS attacks significantly harder.
X-Content-Type-Options
Set to nosniff to prevent browsers from guessing the MIME type. Without it, browsers may execute uploaded files as scripts.
Referrer-Policy
Controls how much URL information is shared when navigating away from your site. strict-origin-when-cross-origin is a good default — sends the origin for cross-origin requests, full URL for same-origin.
Frequently Asked Questions
Monitor Your API Headers Continuously
Checking headers once is useful. Monitoring them 24/7 catches regressions before your users do. PulseAPI checks your endpoints every 10 seconds and alerts you when something changes.