Regular expression that matches valid IPv6 addresses

Answer 1

A simple regex that will match, but I wouldn't recommend for validation of any sort is this:

([A-Fa-f0-9]{1,4}::?){1,7}[A-Fa-f0-9]{1,4}

Note this matches compression anywhere in the address, though it won't match the loopback address ::1. I find this a reasonable compromise in order to keep the regex simple.

I successfully use this in iTerm2 smart selection rules to quad-click IPv6 addresses.