GlossarySEO
What are referring domains?
Also called: linking domains, ref domains, RDs, linking root domains
Definition
Referring domains are the unique websites that link to your site. Ten links from one site count as one referring domain, which is why SEO tools treat referring domains as a better measure than total backlinks.
Referring domains, explained
A single site can link to you hundreds of times: a sitewide footer link, a blogroll, every page of a directory category. Counting all of those as separate backlinks makes a link profile look bigger than it is. Counting unique domains is closer to what matters, which is how many independent sites chose to reference you.
SEO tools build their authority scores on this idea. Ahrefs explains that Domain Rating accounts for both the quantity and quality of the domains linking to a site and how many other unique sites each linking domain links to, with a linking site's value split among the sites it links to. Its Keyword Difficulty score is based on how many referring domains the top ten pages for a query have.
Useful ways to read the number: look at the trend over months, not the absolute count. Look at who they are: a handful of relevant, real sites beat hundreds of scrapers, directories and spam domains, which every site accumulates. Compare yourself with competitors for the queries you want: if every top result has links from 80 domains and you have 5, content alone probably won't close the gap.
Remember that each tool has its own crawler and index, so counts differ between tools and none of them match what Google sees. Google doesn't publish a referring domain score. Search Console's Links report is the closest first-party view, and its numbers rarely match any tool's.
For a new product, the first 20 to 50 relevant referring domains, from a launch, directories, partners, communities and a few articles, often make the biggest difference to how quickly pages get crawled and ranked.
Why it matters for founders
Referring domains are the clearest rough gauge of how many independent sites vouch for you. Tracking them keeps you focused on earning new relevant sites, not piling up links from the same few.
Example
A startup has 1,200 backlinks but only 40 referring domains, because one partner's footer links to it on every page. Its competitors have fewer backlinks and 150 referring domains, and outrank it.
Common mistakes
- Reporting total backlinks as if they were independent votes.
- Comparing counts across different SEO tools.
- Chasing any domain to raise the count, regardless of relevance.
Sources
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Related terms
- BacklinkA backlink is a link from another website to yours. Search engines use backlinks to discover pages and as one signal of which pages are trusted and worth ranking.
- Domain authority (DA and DR)Domain Authority (Moz) and Domain Rating (Ahrefs) are third-party scores, roughly 0 to 100, estimating the strength of a site's backlink profile. They are SEO tool metrics, not Google metrics, and Google doesn't use them.
- Keyword difficultyKeyword difficulty (KD) is an SEO tool's estimate, usually on a 0 to 100 scale, of how hard it is to rank on the first page for a query. Each tool calculates it differently, mostly from the top results' backlinks.
- Link velocityLink velocity is the rate at which a site gains (or loses) backlinks and referring domains over time. SEOs watch it because natural link growth tends to follow real events, while bought links often arrive in unnatural bursts.
- Link buildingLink building is the work of getting other websites to link to yours. Links help search engines discover pages and judge their importance, which is why link quality and how links were earned both matter.