HTTP Header Viewer

What you can learn from headers

• Caching. Cache-Control, ETag and Age show whether browsers and CDNs keep a copy, and for how long. If a change to your site is not showing, these often explain why.
• Compression. Content-Encoding: br or gzip means text is compressed. Missing compression is one of the easiest speed fixes.
• CDN and server. Headers like CF-Ray or X-Cache show a CDN is in front of the site. Server and X-Powered-By often reveal the software underneath.
• Cookies. Each Set-Cookie line, with its Secure, HttpOnly and SameSite flags.

GET or HEAD?

A HEAD request asks for headers without the body, which is lighter. Some servers and frameworks answer HEAD differently from GET, or not at all, so GET is the default because it matches what a browser sends. We stop downloading after the headers either way.

Checking headers yourself

From a terminal, curl -I https://example.com/ sends a HEAD request and prints the headers. Use curl -sD - -o /dev/null https://example.com/ to send a GET instead. In a browser, open developer tools, go to the Network tab, reload, and click the first request.

Limitations

• We see what our server receives. A CDN may send different headers to visitors in other regions, or after a cache warms up.
• Headers added by JavaScript or service workers in the browser do not appear here.