How to Use http-header-diff to Compare HTTP Headers

When debugging inconsistent behavior between different environments or CDNs, HTTP headers can reveal critical clues. The http-header-diff tool helps IT professionals and system administrators compare the HTTP response headers between two URLs in real time. Whether you’re troubleshooting a caching mismatch or identifying extra security headers, this utility streamlines the analysis process.

Instead of manually fetching and comparing headers using curl or browser dev tools, http-header-diff automates the comparison side by side. This improves accuracy and speeds up detection of differences that could be affecting end-user performance, caching, or security compliance.

What is http-header-diff?

http-header-diff is a free, browser-based tool that compares the HTTP headers between two URLs. It fetches each HTTP response—including redirects—and presents a side-by-side diff of all headers. This makes it easy to spot discrepancies in:

• Cache-Control or Expires policies
• CORS headers like Access-Control-Allow-Origin
• Security headers (e.g. Content-Security-Policy, HSTS)
• Custom headers sent by upstream applications or CDNs

The UI requires no installation, making it ideal for quick, low-friction diagnostics.

Common Use Cases

Here are a few real-world situations where http-header-diff provides immediate value:

• Environment drift: Compare staging and production URLs to ensure they respond with the same header suite.
• CDN validation: Confirm if a CDN edge node is modifying or stripping origin headers.
• Cloud migration QA: Compare headers between on-prem and cloud-deployed versions of a service.
• Troubleshooting API issues: Ensure CORS and authentication headers are present in both browser and direct API calls.

Step-by-Step Example

Let’s say you recently migrated a static site to AWS CloudFront and want to verify if headers are consistent with your origin server.

1. Open the Tool

Go to https://allthesystems.com/http-header-diff/ in your browser.

2. Enter the URLs

Enter your origin server URL in the first input:

https://origin.example.com/index.html

Enter the CDN-delivered version in the second input:

https://cdn.example.com/index.html

3. Click “Compare Headers”

The tool will retrieve the URLs via GET requests and perform a diff against their returned response headers.

4. Analyze the Results

Headers that are different or missing will be highlighted. You might see:

Origin version: cache-control: no-cache
CDN version:    cache-control: max-age=31536000, public

In this case, the CDN is applying long-term caching, which may or may not be desirable depending on your deployment strategy.

Pro Tips

• Test multiple paths: Use the tool on several assets (HTML, JS, images) to discover path-specific header behavior.
• Headers change with method: The tool uses a GET request—use curl with POST or custom headers if needed for further checks.
• HTTP version awareness: Headers may vary between HTTP/1.1 and HTTP/2. Use a browser dev tool or curl -I --http2 for more control.

Try http-header-diff Now

Need to troubleshoot inconsistent headers or validate CDN behavior? Use http-header-diff now to diagnose issues quickly and confidently.