curl -I

Use

curl -I https://github.com

What It Does

curl -I asks for HTTP headers without the response body.

Practice

Read the status line first, then headers such as server or location.

Watch Out

Some servers respond differently to header-only requests.

How To Read Output

HTTP/2 200
server: Caddy
content-type: text/html

Read the status line first. 200 means success. 301 or 302 means redirect. 404 means missing path. 502 often means a proxy could not reach a backend service.

Recovery

• Redirected: retry with curl -L -I URL.
• Connection refused: service may not be listening.
• Name resolution failure: test DNS with host or dig.
• TLS or certificate failure: read the exact certificate error before retrying.

Docs Pointers

• Run man curl and search for -I.
• Read curl man page.
• Read MDN HTTP status reference.
• Read curl, curl -v, HTTP, and status codes.