Why does this need a server, unlike most tools here?

Reading another site's response headers from your browser is blocked by CORS, so this check runs through Tool4U's own server instead — the one thing here that genuinely can't run client-side.

Which response is shown if the URL redirects?

The headers of the final response, after all redirects are followed.

Does this tool store the URLs I check?

No — nothing is logged or stored.

HTTP Headers Checker

See every HTTP response header a URL returns.

URL

The URL is fetched from our server (an arbitrary cross-origin fetch isn't possible directly from your browser) — the target site sees this server's request, not your IP, and nothing about the check is stored.

Related tools

Security Headers Checker
URL Parser
HTTP Status Checker
Redirect Chain Viewer

How it works

1
Enter a URL

Including the protocol.
2
Response fetched server-side

Following any redirects first.
3
Every header listed

Full name/value table of the final response.

FAQ

Why does this need a server, unlike most tools here?: Reading another site's response headers from your browser is blocked by CORS, so this check runs through Tool4U's own server instead — the one thing here that genuinely can't run client-side.
Which response is shown if the URL redirects?: The headers of the final response, after all redirects are followed.
Does this tool store the URLs I check?: No — nothing is logged or stored.