Simple HTTPS Health Checks with curl

A browser hides several useful details. A few curl commands can separate DNS, TCP, TLS, redirect, and application problems.

Inspect headers and redirects

curl -I https://example.net/
curl -sS -L -o /dev/null -w '%{http_code} %{url_effective}\n' http://example.net/

Measure connection phases

curl -sS -o /dev/null \
  -w 'connect=%{time_connect} tls=%{time_appconnect} first_byte=%{time_starttransfer} total=%{time_total}\n' \
  https://example.net/

A slow TLS time can point to network loss or certificate-chain work. A fast connection with a slow first byte usually moves attention toward the application.

Test a specific address

curl --resolve example.net:443:203.0.113.10 https://example.net/

--resolve keeps the correct hostname and TLS verification while bypassing normal DNS for one test.