Backlink counts can be misleading. If a local blogger mentions Bean & Barrel Coffee in a sidebar widget that appears on all 1,200 of their posts, Bean & Barrel suddenly has 1,200 backlinks. But it’s still one website vouching for them once. That one website is a referring domain.
Referring domains (sometimes “linking domains” or “ref domains”) count how many separate websites link to you, no matter how many individual links each one contains.
Why they’re a better measure
Earning a link from a new website is harder, and more meaningful, than getting another link from a site that already links to you. Studies of ranking factors have consistently found that the number of referring domains correlates with rankings more closely than the total backlink count. That matches how Google appears to treat links: the first link from a site carries the most weight, and repeats add less.
For comparing yourself with competitors, referring domains give a much fairer picture. One competitor might show 40,000 backlinks from a handful of sitewide links, while another has 900 backlinks from 300 different sites. The second is usually the stronger profile.
What counts as a domain
Tools differ slightly. Most treat news.example.com and blog.example.com as the same referring domain (example.com), while some count subdomains separately. Some also report “referring IPs” or “referring subnets” to spot networks of sites hosted together, which can be a sign of a private blog network.
A local example
Coastline Plumbing has 210 backlinks from 34 referring domains. A competitor has 95 backlinks from 61 referring domains, including the local chamber of commerce, two news sites, a home builders’ association and several suppliers. The competitor’s profile is broader and more convincing, despite having fewer links in total. Coastline’s goal for the year isn’t “more backlinks”; it’s “more referring domains from relevant, local sites”.
Common mistakes
- Celebrating backlink totals that come from one or two sites
- Counting every domain equally. Fifty referring domains from spam directories are worth less than five from respected local and industry sites, and can attract toxic backlinks concerns.
- Ignoring lost referring domains. When a site removes its link, check whether it can be recovered.
- Comparing numbers across tools, which crawl the web differently.
How to check
Search Console’s Links report lists the top linking sites Google knows about. RankThat’s Backlinks feature shows your backlink profile with new and lost links and link building prospects, and its competitor tools let you compare profiles so you can see which sites link to competitors but not to you. Strong link building focuses on growing this number with relevant sites.