What are HTTP Headers?
HTTP headers are metadata sent between clients and servers with each HTTP request and response. They provide information about the request/response, server configuration, security settings, content type, caching directives, and more. Understanding HTTP headers is essential for web development, security analysis, and debugging.
Our free HTTP Headers Checker helps you analyze response headers from any URL. While browser CORS restrictions limit direct header reading from external domains, our tool provides information about common headers and guidance on how to view full headers using browser developer tools or server-side proxies.
Why Check HTTP Headers?
Checking HTTP headers is important for:
- Security analysis and vulnerability assessment
- Verifying CORS configuration
- Checking security headers (CSP, HSTS, X-Frame-Options)
- Debugging API and web application issues
- Analyzing server configuration
- Optimizing caching and performance
Common HTTP Headers
Content Headers
- Content-Type: MIME type of the response (e.g., application/json, text/html)
- Content-Length: Size of the response body in bytes
- Content-Encoding: Compression method (gzip, deflate)
Security Headers
- X-Frame-Options: Prevents clickjacking attacks
- Content-Security-Policy (CSP): Controls resource loading
- Strict-Transport-Security (HSTS): Forces HTTPS connections
- X-Content-Type-Options: Prevents MIME type sniffing
- X-XSS-Protection: Enables XSS filtering
CORS Headers
- Access-Control-Allow-Origin: Specifies allowed origins
- Access-Control-Allow-Methods: Allowed HTTP methods
- Access-Control-Allow-Headers: Allowed request headers
Server Headers
- Server: Server software information
- Date: Response timestamp
- Cache-Control: Caching directives
Key Features
- URL Input: Enter any URL to check headers
- Header Display: View response headers in JSON format
- CORS Information: Guidance on CORS limitations
- Security Analysis: Identify security headers
- Browser Integration: Instructions for using dev tools
Common Use Cases
- Security Audits: Check security header implementation
- API Development: Verify CORS and content-type headers
- Debugging: Troubleshoot header-related issues
- Performance: Analyze caching and compression headers
- Compliance: Verify security header compliance
CORS Limitations
Due to browser CORS (Cross-Origin Resource Sharing) restrictions, HTTP headers from external domains cannot be read directly by JavaScript. To view full headers:
- Browser Developer Tools: Open Network tab, select request, view Headers
- Server-Side Proxy: Use a backend service to fetch headers
- Browser Extensions: Install extensions that bypass CORS
- Command Line: Use curl or wget to view headers
Best Practices
- Use Browser Dev Tools: Most reliable way to view headers
- Check Security Headers: Ensure proper security header implementation
- Verify CORS: Check CORS headers for API endpoints
- Analyze Caching: Review cache-control headers for optimization
- Test Different Endpoints: Check headers across your application
Technical Considerations
Our header checker:
- Attempts to fetch headers using Fetch API
- Shows CORS limitations and workarounds
- Provides guidance for full header inspection
- All processing happens client-side
FAQs
Why can't I see headers from external domains?
Browser CORS restrictions prevent JavaScript from reading headers from external domains. Use browser developer tools or a server-side proxy.
How do I view full headers?
Open browser developer tools (F12), go to Network tab, select a request, and view the Headers section.
Can I check headers from my own domain?
Yes, if the server allows it. However, CORS restrictions still apply to cross-origin requests.
What security headers should I check?
Check for CSP, HSTS, X-Frame-Options, X-Content-Type-Options, and X-XSS-Protection headers.
How do I fix CORS issues?
Configure your server to send appropriate Access-Control-Allow-* headers for allowed origins, methods, and headers.
