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HTTP Header Checker

Analyze your HTTP response headers for security vulnerabilities, performance issues, and SEO problems. Get A+ to F grades across three dimensions, OWASP compliance checks, and copy-paste fix code for Apache, Nginx, IIS, and Cloudflare. Free, instant, 100% browser-based.

How to get your headers:
curl -I https://yoursite.com
Or: Browser DevTools (F12) > Network tab > click request > Response Headers
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How to Use This Tool

  1. Get your headers — Run curl -I https://yoursite.com in a terminal, or open browser DevTools (F12) > Network tab > reload page > click the request > copy Response Headers.
  2. Paste into the input — Paste the raw HTTP response headers into the text area above. The tool accepts headers from curl, DevTools, Postman, or any HTTP client.
  3. Click "Analyze Headers" — Instantly get A+ to F grades for Security, Performance, and SEO. Each header is checked individually with a pass/warn/fail status and plain-English explanation.
  4. Copy the fix code — For every missing or misconfigured header, get copy-paste configuration code for Apache, Nginx, IIS, or Cloudflare Workers. Click "Copy All Fixes" to grab everything at once.

About the HTTP Header Checker

Every time your browser loads a webpage, the server sends back HTTP response headers — invisible metadata that controls how the browser handles the content. These headers determine whether your site is vulnerable to XSS attacks, whether browsers cache your assets efficiently, and whether search engines can properly index your pages.

Most websites are missing critical security headers. According to security research, over 90% of websites lack a proper Content-Security-Policy, and many still expose sensitive information through Server and X-Powered-By headers. Our HTTP Header Checker is the only free tool that analyzes headers across three dimensions — Security, Performance, and SEO — in a single analysis.

What makes this tool different:

  • 3-dimensional grading — Most tools only check security headers. We also analyze performance headers (Cache-Control, Content-Encoding, ETag) and SEO headers (X-Robots-Tag, Content-Type, canonical Link) for a complete picture.
  • OWASP compliance — Security checks are aligned with the OWASP Secure Headers Project recommendations, including newer headers like Cross-Origin-Opener-Policy and Cross-Origin-Embedder-Policy.
  • Fix code for 4 server types — For every issue found, get copy-paste configuration for Apache (.htaccess), Nginx, IIS (web.config), and Cloudflare Workers. No other free tool provides all four.
  • Information leak detection — Flags headers that expose your server software, framework version, or internal architecture to attackers.
  • Plain-English explanations — Every check includes a "what this means" description that non-technical users can understand.

100% browser-based — your headers are analyzed entirely in your browser using client-side JavaScript. Nothing is ever sent to a server. This means you can safely analyze headers from internal servers, staging environments, and localhost without any privacy concerns.

Why Choose Our HTTP Header Checker?

  • Security + Performance + SEO in one tool — Competitors like SecurityHeaders.com only check security. DebugBear only checks caching. We check everything in a single analysis with grades for each dimension.
  • Works with any server — Because you paste headers directly, this tool works with localhost, staging servers, internal networks, and any server behind a firewall. URL-based checkers can't reach these.
  • Copy-paste fix code — Don't just learn what's wrong — get the exact configuration to fix it. Switch between Apache, Nginx, IIS, and Cloudflare tabs to get code for your specific server.
  • OWASP-aligned security checks — Our 12-header security analysis follows the OWASP Secure Headers Project, including modern headers like COOP, COEP, and CORP that many tools still don't check.
  • Sample headers for learning — Load pre-built samples (A+ secure site, F insecure site, WordPress default, CDN-served) to understand what good and bad headers look like before analyzing your own.
  • Downloadable report — Export your full analysis as a text report to share with your development team or include in security audits.

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Frequently Asked Questions

What are HTTP response headers?
HTTP response headers are metadata sent by a web server along with every page it serves. They control how browsers handle the content — including caching behavior, security policies, content type, encoding, and more. Headers like Content-Security-Policy, Strict-Transport-Security, and Cache-Control are critical for website security, performance, and SEO. You can view them in browser DevTools under the Network tab or by running curl -I from a terminal.
Which security headers should every website have?
At minimum, every website should implement these six security headers: Content-Security-Policy (prevents XSS and code injection), Strict-Transport-Security (forces HTTPS connections), X-Content-Type-Options: nosniff (prevents MIME-type sniffing), X-Frame-Options (prevents clickjacking), Referrer-Policy (controls referrer information leakage), and Permissions-Policy (restricts access to browser APIs like camera and microphone). For maximum security, also add Cross-Origin-Opener-Policy, Cross-Origin-Resource-Policy, and Cross-Origin-Embedder-Policy.
How do I get my HTTP response headers?
Three easy methods: (1) Command line: Run curl -I https://yoursite.com to get just the headers. (2) Browser DevTools: Press F12, go to the Network tab, reload the page, click on the main document request, and look at the "Response Headers" section. (3) Postman or similar tools: Send a HEAD or GET request and copy the response headers. Then paste them into our analyzer for a full audit.
What is Content-Security-Policy (CSP) and why is it important?
Content-Security-Policy is the most powerful HTTP header for preventing Cross-Site Scripting (XSS) attacks. It tells the browser exactly which sources of content (scripts, styles, images, fonts, etc.) are allowed to load on your page. If an attacker manages to inject a malicious script, CSP blocks it from executing because it doesn't come from an approved source. A well-configured CSP is considered the gold standard of web application security.
What is HSTS and how does it protect my site?
HTTP Strict Transport Security (HSTS) tells browsers to always use HTTPS when connecting to your site. Once a browser receives this header, it automatically upgrades all future HTTP requests to HTTPS — even if someone types http:// in the address bar. This protects against protocol downgrade attacks and cookie hijacking. The recommended value is max-age=31536000; includeSubDomains; preload which enforces HTTPS for one year across all subdomains and qualifies for the HSTS preload list.
How do caching headers affect performance?
Caching headers like Cache-Control, ETag, and Expires tell browsers and CDNs how long to store your files before requesting them again. Proper caching can dramatically reduce page load times — a returning visitor with cached assets may load your page 5-10x faster. For static assets (CSS, JS, images), set Cache-Control: public, max-age=31536000 (1 year). For HTML pages, use shorter durations like max-age=3600 (1 hour) or no-cache with ETag for always-fresh content.
What does the X-Robots-Tag header do for SEO?
X-Robots-Tag is the HTTP header equivalent of the <meta name="robots"> tag. It tells search engine crawlers whether to index a page, follow its links, cache it, or show snippets in search results. Unlike the meta tag, X-Robots-Tag works on non-HTML files too — PDFs, images, videos, etc. A misconfigured X-Robots-Tag with noindex can accidentally de-index pages from Google. Always verify this header when troubleshooting indexing issues.
What does an A+ security grade mean?
An A+ grade means your site has all critical security headers properly configured and doesn't leak sensitive information through headers like Server or X-Powered-By. It indicates full OWASP compliance for HTTP header security. Most websites score C or below — achieving A+ puts you in the top percentile. The grade is based on which headers are present, whether they're correctly configured (not just present but set to secure values), and whether information-leaking headers are removed.
How do I fix missing security headers?
After analyzing your headers, our tool generates exact fix code for your server type. Click the server tab (Apache, Nginx, IIS, or Cloudflare) and copy the configuration. For Apache, add the lines to your .htaccess file. For Nginx, add them to your server block in nginx.conf. For IIS, add them to web.config. For Cloudflare, use a Workers script. After applying changes, restart your server and re-analyze to verify.
Is my data safe using this tool?
Completely safe. All analysis happens 100% in your browser using client-side JavaScript. Your headers are never uploaded to any server, never logged, and never stored anywhere except optionally in your browser's localStorage as a draft. This means you can safely analyze headers from internal servers, staging environments, and localhost without any privacy concerns. Close the tab and it's gone.

Need Help Securing Your Website?

Our Technical SEO and Website Development experts can configure your server headers, implement security best practices, and optimize performance — so you can focus on growing your business.

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