Quite often in my life I need to know what my ip is, very often when I need to know this I'm at a terminal.
My old go-to-site for checking my IP has always been https://minip.no, simply because it's short to type, even though I'm not even norwegian …
This site runs on Pelican, a static site generator. That means the site is already very small, but why stop there? If something's worth doing it's worth overdoing. Using sed has the advantage of not having to install anything, because it's already available on all sane operating systems.