What are referring domains?

Referring domains are the unique domains that have at least one link pointing to a given page or to a whole site. Each domain counts once, however many links it sends.

Referring domains vs. backlinks

A backlink is a single link; a referring domain is the source those links come from. The difference is easiest to see with numbers. A partner puts a link to your site in its footer, so the link appears on every one of its 500 pages. An SEO tool will report 500 backlinks and exactly 1 referring domain. Twenty links from twenty different industry sites, on the other hand, are 20 backlinks and 20 referring domains.

That is why the number of domains tells you more about a link profile than the number of links. The tenth link from the same site adds little independent signal compared with a first link from a new, topically related domain. Treat this as reasoning, not as a disclosed ranking formula: Google does not publish how it weighs links.

How SEO tools count them

Ahrefs, Semrush, Majestic and Moz each run their own crawler, keep their own index and apply their own rules: whether subdomains are counted separately, whether nofollow links are included, how long a removed link stays in the database. The same web therefore produces different numbers in each tool. Comparisons only make sense within one tool and over time, for example your site against a competitor in Ahrefs, never an Ahrefs figure against a Semrush figure. The Ahrefs vs. Semrush comparison covers where the two diverge.

Google Search Console has its own view in the "Links" report, under "Top linking sites". It is a sample of Google's data, not a complete list. Domain Rating (Ahrefs) and Domain Authority (Moz) are models built by third parties, not Google metrics.

What makes a referring domain valuable

Topical fit — a link from a site in your industry, or in your customers' industry, carries more meaning than one from a random directory.
Link placement — an editorial link in the body of an article is a different thing from a link in a footer, a sidebar or a list of partners.
Real traffic on the linking site — a site people actually read is a more credible source than one that exists only to link out.
Anchor text diversity — a natural profile mixes brand names, bare URLs and descriptive phrases instead of repeating one exact-match keyword.
Rel attributes — nofollow, sponsored and ugc. Since 2019 Google has treated them as hints rather than strict directives. Under Google's spam policies, paid links should carry rel="sponsored"; rel="nofollow" is also acceptable.

How to monitor referring domains

New and lost domains. Losing a domain that has linked to you for years can matter more than gaining a few new links. Check the cause, because some losses are reversible, for instance when a link disappeared during a redesign of the linking page.
Link gap against competitors. Domains that link to competitors but not to you make a ready-made prospecting list for link building.
Sudden spikes. A burst of low-quality domains may be spam. It is worth analyzing before doing anything about it.

Building and maintaining a healthy set of referring domains is an ongoing part of SEO, alongside work on content and on the technical side of the site.

Common mistakes

Chasing the number of domains instead of their quality and relevance.
Comparing figures taken from different tools.
Ignoring lost domains.
Buying sitewide footer links, which add hundreds of backlinks from one domain and a risk of violating Google's spam policies.
Treating DR as a Google ranking signal.
Reaching for the disavow tool by default. Google states that most sites do not need it; the toxic links entry explains when it is actually worth the effort.

Related terms

Backlink — a single link; referring domains are where backlinks come from
Link building — earning links, ideally from new, topically related domains
Domain Rating — an Ahrefs metric calculated partly from the number and strength of referring domains
Link equity — the value a link passes to the page it points to
Toxic links — links that may do harm, and when they are really worth dealing with
Broken link building — winning new domains by offering a replacement for a dead link

Referring Domains

What are referring domains?