HTTP Header Checker

Inspect raw server response headers instantly. Audit Cache-Control, CORS, and critical Security headers.

Bypassing the Browser Sandbox

Because browsers actively hide critical security headers from Javascript, we route your request through a dedicated Asynchronous Python connection to fetch the exact, unadulterated dictionary of responses in milliseconds.

Async Bulk Queues

When processing massive CSV files containing hundreds of domains, we upload the data to a Redis worker queue. The background python script maps the headers concurrently without ever blocking or crashing the primary API.

Frequently Asked Questions

To protect user privacy and prevent Cross-Site Scripting, browsers intentionally strip or hide critical security headers (like HSTS or CSP) from JavaScript APIs. Using a public proxy injects fake headers. Our tool uses a raw Python connection to pull the exact dictionary.

We utilize Python's AsyncIO alongside the HTTPX library. This means our server can handle millions of requests without ever blocking the main processing thread, returning untouched raw data in milliseconds.

For security, ensure you have Strict-Transport-Security (HSTS) and X-Frame-Options. For performance, look at Cache-Control to ensure your assets are being properly cached by CDNs.

Yes, both single tracing and massive bulk analysis are 100% free.

Chasing a Cross-Origin Problem?

This tool shows you every response header. When the ones you care about are the Access-Control-* set, our CORS tester goes further — it sends a real preflight OPTIONS request and tells you which specific check failed.

Worth knowing before you dig in: a header missing here may simply not be sent on error responses. Plenty of frameworks add CORS headers in middleware that never runs when a route throws, which is covered in fixing the No Access-Control-Allow-Origin error.

Ready to send a full request with a body and auth? The API tester handles the round trip.