I've long been curious how exactly they determine the "registered domain", and your comment made me finally look for the answer. It looks like they use (and sem

I've long been curious how exactly they determine the "registered domain", and your comment made me finally look for the answer. It looks like they use (and semi-manually maintain) a list of "effective TLDs": https://www.publicsuffix.org/ https://www.publicsuffix.org/ The maintenance process is described here: https://github.com/publicsuffix/list/wiki/Guidelines https://github.com/publicsuffix/list/wiki/Guidelines