Referring domains count how many distinct websites link to you. If one blog links to you 40 times from its sidebar, that is 40 backlinks but one referring domain. SEO practitioners often watch referring domains more closely than raw backlink counts because the number is harder to inflate and says more about how widely your site is cited.
Backlinks versus referring domains
Backlink totals swing wildly for reasons that have nothing to do with your reputation. A site-wide footer link on a large site can add thousands of backlinks overnight, and a redesign that removes it can take them away just as fast. The referring domain count barely moves in either case.
Getting a link from a new site usually means a new person decided to reference you. That is why growth in referring domains is often a better sign of real progress than growth in backlinks.
How tools count them
Each SEO tool has its own crawler, index, and rules. Some count subdomains separately, some group them under the root domain, and each discovers and drops links on a different schedule. The same site can show noticeably different referring domain counts in Ahrefs, Semrush, Moz, and Search Console.
Pick one tool for trend tracking and stay with it. Comparing numbers across tools mostly measures the differences between their crawlers.
Using referring domains in competitive research
Comparing referring domains between your site and the sites ranking for your target keywords gives a rough sense of the gap. The more useful step is looking at which domains link to several competitors but not to you. Those are often directories, review sites, partner pages, or publications that cover the category, and they are good outreach targets because they have already shown they link to products like yours.
- Export referring domains for three to five competitors
- Filter to domains linking to at least two of them
- Remove domains already linking to you
- Group what is left by type: directories, partners, media, communities
Quality still matters more than count
A referring domain count treats a respected industry publication and an abandoned scraper site as equal. Google does not. Use the count as a tracking metric and review the actual domains behind it before drawing conclusions.
Example
Finding gaps for an invoicing product
An illustrative invoicing tool, Billkite, compares its referring domains against two competitors. It finds a dozen accounting software directories and two bookkeeping associations that link to both competitors but not to Billkite. Several have free listing forms, which makes them the first items on the outreach list.
Common mistakes
Reporting backlink totals as progress
A jump in backlinks from one site-wide link looks impressive and means very little. Report referring domains, and note which new domains matter.
Comparing counts across different tools
Each tool's index is different. A higher number in one tool than another is not evidence of anything about your site.
Questions
It can help the specific page it points to and send traffic, but most practitioners assume additional links from a domain that already links to you add less than a link from a new domain. Google has not published exact rules.
Google does not publish a referring domain metric. It is a concept used by SEO tools to summarize link profiles.
