Sometimes, it’s really helpful to know what your public IP address is. If you use VPNs, or have IP-restricted security measures in place, knowing your public IP address can be a vital piece of information.
For example, I use my IP address to lock down my MySQL server access, when I am performing maintenance and enhancements. If my IP changes, then I reconfigure the access. I need to know what the server sees on the last visible hop (the external IP address at my premises isn’t always the same.)
When needing to do just that, I found a neat online tool called what-is-my-ipaddress.com, and what is cool about this one (above all the other ones you can find online) is that I can save my history into my browser, so I can see how my IP address has changed over time. Really useful, if your ISP assigns you addresses from different ranges (like mine).
Of course, it’s free to use! And it’s not emblazoned with loads of ads and other guff like some of the other sites that provide this service.