How would you parse a url in Ruby to get the main domain?

Question

I want to be able to parse any url with ruby to get the main part of the domain without the www (just the XXXX.com)

Answer 1

Please note there is no algorithmic method of finding the highest level at which a domain may be registered for a particular top-level domain (the policies differ with each registry), the only method is to create a list of all top-level domains and the level at which domains can be registered.

This is the reason why the Public Suffix List exists.

I'm the author of PublicSuffix, a Ruby library that decomposes a domain into the different parts.

Here's an example

require 'uri/http'

uri = URI.parse("http://toolbar.google.com")
domain = PublicSuffix.parse(uri.host)
# => "toolbar.google.com"
domain.domain
# => "google.com"

uri = URI.parse("http://www.google.co.uk")
domain = PublicSuffix.parse(uri.host)
# => "www.google.co.uk"
domain.domain
# => "google.co.uk"