Free HTTP Headers Lookup — Check Server Response Headers & Status Codes Online

What Is an HTTP Headers Lookup?

An HTTP headers lookup is the process of inspecting the metadata exchanged between a web browser (client) and a web server during an HTTP request. Every time you visit a website, your browser sends request headers and the server responds with response headers — containing critical information like status codes, content types, caching rules, security policies, and more.

Our free HTTP Header Checker lets you instantly view all response headers for any URL — helping you diagnose issues, optimize performance, and improve your website's SEO.

Why HTTP Headers Matter for SEO & Web Performance

HTTP headers play a crucial behind-the-scenes role in how search engines crawl, index, and rank your website. Here's why they matter:

• Status Codes (200, 301, 404, 500) — Tell search engines whether a page is live, redirected, broken, or experiencing server errors
• Cache-Control & Expires — Determine how browsers and CDNs cache your content, directly impacting page speed
• Content-Type — Ensures the server delivers the correct MIME type so browsers render pages properly
• X-Robots-Tag — Controls indexing directives at the HTTP level, complementing meta robots tags
• Security Headers (HSTS, CSP, X-Frame-Options) — Protect your site and boost trust signals
• Canonical & Link Headers — Help search engines understand preferred URLs and pagination

Key HTTP Response Headers Explained

Understanding the most important headers helps you troubleshoot and optimize effectively:

• Content-Type — Specifies the media type (e.g., text/html, application/json)
• Cache-Control — Defines caching directives like max-age, no-cache, no-store
• Location — Used with 3xx redirects to specify the destination URL
• Server — Identifies the web server software (e.g., Nginx, Apache, Cloudflare)
• Strict-Transport-Security (HSTS) — Forces HTTPS connections for enhanced security
• Content-Encoding — Indicates compression methods like gzip or br (Brotli)
• Set-Cookie — Manages cookies sent from the server to the browser

How to Use the HTTP Headers Lookup Tool

1. Enter the URL you want to inspect in the input field above
2. Click the Submit button to send the request
3. Review the full list of response headers returned by the server
4. Check the HTTP status code to confirm the page is responding correctly
5. Look for caching, security, and SEO-related headers to identify optimization opportunities

Common Use Cases

• Debugging redirects — Verify 301/302 redirect chains and their destination URLs
• Checking security headers — Ensure HSTS, CSP, and X-Frame-Options are configured
• Validating caching — Confirm Cache-Control and Expires headers are set for performance
• SEO audits — Check X-Robots-Tag, canonical headers, and status codes
• API troubleshooting — Inspect CORS headers and content types for API endpoints
• Compression checks — Verify gzip or Brotli compression is enabled

Best Practices for HTTP Headers

• Always return proper status codes — 200 for live pages, 301 for permanent redirects, 404 for missing pages
• Enable HSTS to enforce HTTPS and protect users from downgrade attacks
• Set appropriate Cache-Control headers to improve load times and reduce server load
• Use Content-Security-Policy (CSP) to prevent XSS and injection attacks
• Enable gzip or Brotli compression to reduce page size and improve Core Web Vitals
• Remove unnecessary headers like Server version info to reduce attack surface

Related SEO Tools

Explore more tools to analyze and optimize your website:

• HTTP/2 Checker — Verify if your server supports the faster HTTP/2 protocol
• SSL Lookup — Check your SSL certificate details and expiration
• DNS Lookup — Query DNS records including A, CNAME, MX, and NS records
• Website Hosting Checker — Find out who hosts any website
• Safe URL Checker — Verify if a URL is safe from malware and phishing

Frequently Asked Questions

What are HTTP headers?

HTTP headers are metadata sent between a client (browser) and server during web requests. They contain information about the request and response — including content type, caching rules, security policies, cookies, and status codes. Headers are invisible to regular users but essential for how websites function.

How do HTTP headers affect SEO?

HTTP headers directly impact SEO through status codes (telling search engines if pages are live or broken), caching headers (affecting page speed — a ranking factor), X-Robots-Tag (controlling indexing), and security headers (building trust). Misconfigured headers can cause crawl errors, duplicate content issues, and slow load times.

What is a good HTTP status code?

A 200 OK status code means the page loaded successfully — this is what you want for all your live pages. A 301 Moved Permanently is correct for permanent redirects. You should fix any 404 Not Found or 500 Internal Server Error responses, as these harm both user experience and SEO.

How can I check if my website has security headers?

Use this HTTP Headers Lookup tool to check for security headers like Strict-Transport-Security, Content-Security-Policy, X-Content-Type-Options, and X-Frame-Options. If any are missing, configure them in your web server (Nginx, Apache) or CDN settings.