One of my most used scripts, I snagged of GitHub way back in 2010: headers.

It’s stupidly simple:

#!/bin/sh

curl -sv "$@" 2>&1 >/dev/null |
	grep -v "^\*" |
	grep -v "^}" |
	cut -c3-

And I use it like this:

headers https://www.example.com/

Or if I want to follow redirects:

headers -L https://www.example.com/

I know there are plenty of cooler tools out there, but this has treated me well for 13 years now and works everywhere. I highly recommend throwing it in your bin, too.