Online HTTP Header Checker and Security Inspector
Analyze response headers with our free HTTP header checker. Audit security headers, CORS settings, and cache rules instantly online. Inspect your URL now.
About HTTP Header Checker
The HTTP Header Checker lets you inspect server response headers for any web address or API endpoint. Designed for web developers, system administrators, and security professionals, it delivers an instant breakdown of status codes, server signatures, caching instructions, and connection parameters.
Running directly in your browser without software installations or signups, Doffl provides a clean, fast way to diagnose routing issues, verify CORS configurations, and audit critical security policies across your infrastructure.
Key features
- Inspect status codes and full HTTP response headers
- Audit core security headers like CSP and HSTS
- Verify CORS headers and cross-origin permissions
- Analyze Cache-Control and Expires directives
- Identify server software and CDN proxy layers
- Runs client-side in your browser with no installation
How to use HTTP Header Checker
- Enter the target web address including http or https protocol.
- Click the analyze button to send the request.
- Examine the returned HTTP status code and response timing.
- Review specific sections for security, caching, and CORS headers.
Who is it for?
- Web developers troubleshooting API headers and redirect chains
- Security engineers verifying HSTS, X-Frame-Options, and Content-Security-Policy rules
- Frontend developers resolving cross-origin resource sharing (CORS) errors
- DevOps engineers testing cache invalidation and CDN edge server responses
Frequently asked questions
What is an HTTP header?
An HTTP header is a key-value pair transmitted between a client and a web server. Headers define communication parameters such as content type, caching policies, authentication tokens, and security configurations.
Why are security headers important?
Security headers instruct the user's browser on how to handle site content safely. Correctly configured headers protect applications against vulnerabilities like cross-site scripting (XSS), clickjacking, and unauthorized data framing.
How does this tool check CORS headers?
The tool inspects headers such as Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers returned by the target host, allowing you to see if external domains can query the resource.
Can I check HTTP headers for HTTPS websites?
Yes. The tool inspects both plain HTTP and encrypted HTTPS URLs, including TLS-specific response details and HSTS configurations.
Is this HTTP header checker free?
Yes, this tool is completely free to use with no account creation or subscription required.