The number of unique websites that link to a given page or domain.
Referring domains (RDs) is the count of unique websites that have at least one backlink pointing to a given URL or domain. It is distinct from the total number of backlinks, which counts all links including multiple links from the same domain.
Referring domains is generally a better signal of link authority than raw backlink count. 100 links from 100 different sites is a stronger signal than 100 links all from the same site. Google appears to weight the diversity of your backlink profile — how many independent sources endorse your site — not just volume.
In competitive analysis, referring domain counts for ranking pages give a practical benchmark for link building targets. Our B2B backlink benchmark research found that median referring domains for top-5 ranking pages vary significantly by industry — from relatively few for niche B2B topics to hundreds for highly competitive verticals.
Sudden large increases in referring domains (especially from low-quality sites) can be a signal of negative SEO or a link scheme, which Google may penalise. Natural link profiles grow at a reasonable, consistent rate.
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