What is a referring domain?
A referring domain is a website that links to your site at least once. If a news site links to you from three different articles, you have three backlinks but one referring domain. If a blog adds your link to its footer and the footer appears on 2,000 pages, you have about 2,000 backlinks and still one referring domain.
SEO tools report referring domains alongside backlinks because the two numbers tell different stories. Backlinks measure volume. Referring domains measure breadth: how many separate websites chose to link to you at all.
The term is sometimes written "linking domains" or "linking root domains". All three mean a count of unique websites, not a count of links.
What is the difference between referring domains and backlinks?
The difference between referring domains and backlinks is that a backlink is a single link, while a referring domain is the website the link comes from, counted once however many links it sends. One referring domain can account for one backlink or thousands.
| Backlinks | Referring domains | |
|---|---|---|
| What is counted | Every individual link | Every unique linking website |
| A footer link on 2,000 pages | About 2,000 | 1 |
| Three links from one article | 3 | 1 |
| Easy to inflate? | Yes, with one sitewide link | Harder, needs more separate sites |
| What it suggests | Link volume | Breadth of independent support |
The gap between the two numbers is often more informative than either number alone. A site with 50,000 backlinks from 40 referring domains almost certainly has a few sitewide links doing most of the work. A site with 600 backlinks from 400 referring domains has links spread across many independent sites.
Why do referring domains matter for SEO?
Referring domains matter for SEO because links from many independent websites are harder to manufacture than many links from one website. A thousand links from one domain is still one site's opinion, repeated. A hundred links from a hundred unrelated, real websites is a hundred separate opinions.
That reasoning is why SEOs treat referring domain growth as a better progress measure than raw backlink growth. It is a rule of thumb, not a published rule. Google does not publish a referring domain metric, does not say how it weighs a second link from the same website, and does not confirm that it counts domains the way SEO tools do. Any statement that a fixed number of referring domains is "needed" to rank is a guess.
How do you check referring domains?
To check referring domains, open a backlink tool, enter your domain, and read the referring domains figure rather than the backlinks figure. Google Search Console's Links report shows the sites linking to you as Google sees them, and is the only free view drawn from Google's own data.
Three settings change the number a tool shows:
- Scope. A count for the whole domain, a subdomain, or one URL will differ. Check you are comparing like with like.
- Link type. Most tools count nofollow,
sponsoredandugclinks as referring domains unless filtered. Filter to followed links if you want only domains that can pass ranking value. - Lost links. Some tools keep counting domains whose link has since been removed. Use the "live" or "current" view.
Different tools crawl different parts of the web, so their referring domain counts never match each other or Search Console. Compare a site against itself over time in one tool, not across tools.
Do nofollow links count as referring domains?
Yes, most SEO tools count a website that only gives nofollow links as a referring domain, unless you filter for followed links. That matters when judging a link profile, because a large share of real links are nofollow. HTTP Archive's 2024 Web Almanac found nofollow on 32.7% of mobile pages [6].
Business listings show the gap clearly. Search Insider checked the website link on live business listings across the 300 sites in Foundation Links [4]. Of the 192 sites that link to the business's website at all, 113 mark the link nofollow, sponsored or ugc, and 74 leave it followed [4]. A new business listed on all 192 would gain up to 192 referring domains in most tools, but fewer than half would be followed. Google treats nofollow as a signal that the linking site does not want to be associated with the destination [5].
Can referring domains be faked?
Yes, referring domains can be faked, and that is the main weakness of the metric. Link farms, groups of websites that all link to each other to raise rankings, date back to 1999 [2]. Private blog networks are a newer version of the same idea, and Google began issuing manual actions against them in September 2014 [2]. Search Insider does not support or suggest the use of private blog networks.
Google's spam policies name the methods used to manufacture links across many domains, including "excessive link exchanges", "using automated programs or services to create links to your site" and "widely distributed links in the footers or templates of various sites" [1]. Google's Penguin algorithm targeted this kind of link manipulation from April 24, 2012, and since Penguin 4.0 on September 23, 2016, it has worked in real time and discounts the links, ignoring them rather than counting them [3].
The practical result: a referring domain count rises just as fast with fake domains as real ones, but only the real ones are likely to count.
How has the way referring domains are judged changed?
Referring domains were once judged mostly by how many there were; since Google's link spam crackdowns, they are judged by whether each domain is a real site with a reason to link. The shift tracks Google's response to link farms and link schemes.
1999: link farms exploit link popularity
Link farms appeared in 1999, when SEOs exploited the Inktomi search engine's reliance on link popularity [2]. More linking sites meant better rankings, so people built networks of sites to supply them.
2012: Penguin targets manipulative links
Google launched Penguin on April 24, 2012, affecting about 3.1% of English queries [3]. Penguin targeted link manipulation such as link buying, link farming and automated links [3]. Domain counts built from networks became a liability.
2016: Penguin discounts links in real time
From September 23, 2016, Penguin became part of Google's core algorithm and ran in real time [3]. Under Penguin 4.0, manipulative links are ignored and no longer count toward rankings [3], so a padded referring domain count stops working rather than staying high.
How do you judge the quality of a referring domain?
To judge the quality of a referring domain, check whether it is a real website that people visit, whether its topic relates to yours, and whether the link sits in content a reader would see. One relevant, trusted referring domain outweighs dozens of empty ones.
Questions to ask of each referring domain:
- Is it real? It has original content, a clear owner and visitors, not pages of links.
- Is it relevant? Its topic or audience overlaps with yours.
- Is the link editorial? It was placed by the site's owner because it helps readers, not paid for or swapped.
- Is it one domain or many in disguise? Several "different" domains sharing the same design, owner or content are one source, whatever a tool counts.
How many referring domains do you need?
There is no fixed number of referring domains needed to rank, and Google has never published one. The useful benchmark is the pages already ranking for your target query: if they each have links from a few hundred real, relevant websites and your page has ten, the gap is real.
Grow referring domains by earning links from more distinct, relevant sites, not by adding links from sites that already link to you. A new referring domain adds breadth. A fiftieth link from the same domain adds almost nothing.