HTTP header checker
Every web page comes with a set of hidden notes called HTTP headers. They tell the browser what kind of file it is getting, how long to keep it, which server sent it, and which security rules to follow.
This tool loads the address, follows any redirects, and shows you the headers of the final page, together with the status code, response time and the server’s IP address.
How to read the results
- Status code says whether the request worked. 200 is fine, 3xx is a redirect, 4xx is a problem with the request and 5xx is a server error.
- Cache-Control and Expires decide how long browsers and CDNs may keep a copy.
- Content-Type tells the browser what kind of file it received.
- Server and X-Powered-By can reveal the software in use, which some sites choose to hide.
- Strict-Transport-Security, Content-Security-Policy and similar headers are security settings. The security headers checker scores them.
Questions
Why do I see headers from a different address than I typed?
We follow redirects like a browser does, so you see the headers of the page you would finally land on. The redirect count is shown above the headers.
Can I use this to see if a CDN is in use?
Often, yes. Headers such as cf-ray, x-served-by or via usually give a CDN away.
Why does the status code differ from my browser?
Some sites answer automated tools differently from browsers. A 403 or 429 here can mean the site blocks tools like ours.
Related guides
More free tools
- DNS lookup
- SSL certificate checker
- Redirect checker
- WHOIS and domain expiry
- MX record lookup
- Robots.txt checker
- Security headers checker
Results are a snapshot taken from our servers at the moment you ask, and can differ from what you see elsewhere. siteupdown.com tests public websites only. Spotted a problem?