🛡️ I Built a Free HTTP Header Analyzer — and Most Sites Score an F

A few months ago, I was reviewing the Nginx configuration of a side project and decided to run it through a security headers scanner. I pasted the response headers into a popular online tool, hit Enter, and waited.

Grade F. 12/100.

I was stunned. I had HTTPS, a valid certificate, and a modern stack. But I was missing every critical security header. No HSTS, no CSP, no X-Frame-Options. My site was a sitting duck for clickjacking, XSS, and protocol downgrade attacks, and I didn’t even know it.

That experience led me to build DevToolbox HTTP Header Analyzer — a completely client-side tool that grades your security headers from A+ to F, explains every single one in plain English, and gives you ready-to-paste fixes. And it never sends your headers to any server.

Try It Yourself in 15 Seconds

1. Open the HTTP Header Analyzer in a new tab.
2. Copy the headers below (a well-configured example that scores A+).
3. Paste them into the tool, click Analyze headers, and watch the magic happen.

HTTP/2 200 OK
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none'
X-Frame-Options: DENY
X-Content-Type-Options: nosniff
Referrer-Policy: strict-origin-when-cross-origin
Permissions-Policy: camera=(), microphone=(), geolocation=()

You’ll see an A+ badge, a security score of 97/100, and a detailed breakdown of every header. Each line is explained — what it does, what happens if it’s missing, and how to fix it.

Now paste this insecure configuration instead, just to see the contrast:

HTTP/1.1 200 OK
Server: Apache/2.4.51 (Ubuntu)
X-Powered-By: PHP/8.1.0

Grade F. One critical header, two warnings, and zero protections.

What Makes This Different from Other Scanners?
100% client-side — your headers never leave your browser. No data is sent to any server, ever. You can even disconnect from the internet after loading the page and it still works.

Plain-English explanations — you don’t just get a checklist of missing headers. Each one is described in simple terms: what it protects against, what the recommended value is, and how to configure it on Nginx, Apache, Express, or Vercel.

Before/After comparison mode — making changes to your server config? Paste your old headers and your new headers side by side to see exactly what improved.

It’s not just about security — Cache-Control, CORS, Content-Type, and even informational headers like Server and X-Powered-By are analyzed and explained.
A Real Example from My Own Server
After that humiliating F grade, I spent ten minutes pasting the recommended fixes into my Nginx config:
add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
add_header X-Frame-Options "DENY" always;
add_header X-Content-Type-Options "nosniff" always;
add_header Referrer-Policy "strict-origin-when-cross-origin" always;
add_header Permissions-Policy "camera=(), microphone=(), geolocation=()" always;
add_header Content-Security-Policy "default-src 'self'; object-src 'none'; base-uri 'self';" always;
server_tokens off;
I reloaded Nginx, re-pasted the response headers into the analyzer, and the grade jumped from F to A+. Ten minutes to go from a security disaster to a solid configuration.

Part of a Bigger Toolbox
The HTTP Header Analyzer is one of several free, client-side tools I’ve built under the DevToolbox umbrella. No sign-ups, no ads, no data collection. Every tool runs entirely in your browser.

You might also find these useful:

 JWT Decoder & Security Analyzer — spots alg: none, algorithm confusion, and expired tokens

 Unix Timestamp Converter — all formats, UUID v1/v7 decoder, ObjectID timestamps

 SQL Formatter & Explainer — format, detect anti-patterns, convert dialects

Go grab your response headers (from DevTools → Network → Headers, or curl -I https://yoursite.com), paste them into the analyzer, and see what score you get. You might be surprised.

🔗 Try the HTTP Header Analyzer now