Referring Domain

A referring domain is a unique website that has at least one backlink pointing to your site. If a single domain links to you from 200 different pages, that still counts as one referring domain — but 200 backlinks.

Most SEO tools (Ahrefs, Moz, Semrush) emphasize referring domains over raw backlink counts because the metric is harder to game. Buying 10,000 spammy links from 5 PBNs registers as 5 referring domains, not 10,000.

A healthy growth pattern is steady referring-domain growth in line with content output. Spikes followed by drops usually indicate manipulation that Google later devalues.