Referring Domains vs Backlinks: What's the Difference?

Backlinks are the total number of individual links pointing at your site. Referring domains are the number of unique websites those links come from. If one site links to you 300 times, that's 300 backlinks and one referring domain — and for SEO purposes, the second number is the one that describes your actual position.

The difference in one example

Two sites, both reported by an SEO tool:

	Site A	Site B
Backlinks	4,000	400
Referring domains	12	380
Backlinks per domain	333	1.05

Site A's dashboard looks ten times better. Site B is in a dramatically stronger position, because 380 separate site owners independently decided to link to it, while Site A has been endorsed by twelve — most of whom are probably running site-wide footer or sidebar links that repeat on every page they publish.

Search engines are trying to measure endorsement. Twelve endorsements repeated 4,000 times are still twelve endorsements.

Why the second link from the same site counts for so much less

The first link from a new domain carries the most weight. The second carries less. By the fiftieth, the incremental value is close to nothing.

This isn't a rule Google publishes as a number, and it's worth being precise about what is and isn't known. Google does not ignore all but one link per domain — that's a common myth. Multiple links from the same site can each carry value, particularly when they sit in different contexts on genuinely different pages. What's consistently observed is steep diminishing returns: link acquisition curves flatten hard within a single domain, and every credible correlation study finds referring-domain count tracks ranking far more closely than raw link count.

The intuition behind it is straightforward. A backlink is a vote. Letting one voter cast 4,000 ballots would make the whole system trivial to game, so any sane ranking system caps how much any single source can contribute.

What the ratio tells you

Divide backlinks by referring domains. The result is a fast diagnostic.

1 to 3 backlinks per domain — the normal editorial pattern. Sites link to you once, occasionally twice.
4 to 10 — common and usually fine. Blogs that cite you repeatedly, forum threads, sites with archive and category pages that repeat the link.
20+ — investigate. This is almost always site-wide links: a footer, a sidebar widget, a blogroll, or a template that repeats your link across every page of a site.

A high ratio isn't automatically bad, but it does mean your backlink count is describing far less reach than it appears to. It's also the most common way a paid link package inflates its numbers — one blogroll placement on a 5,000-page site reports as 5,000 backlinks.

The related distortion runs the other way. Some tools count every URL variant separately (http and https, with and without www, tracking parameters), which inflates backlink counts without a single extra site being involved. Referring domains is immune to that noise, which is another reason it's the more stable metric.

Which one should you track?

Track referring domains as your growth number. It's the metric that reflects real progress, it's hard to inflate accidentally, and it's what the authority scores are mostly built from — Ahrefs' Domain Rating is calculated from unique dofollow referring domains, not from link count, as Ahrefs' own glossary entry spells out.

Use backlinks as a diagnostic. When the number moves sharply and referring domains don't, something structural changed — a site added or removed a template link, or a tool changed how it deduplicates. That's useful to know, but it isn't growth.

Watch the trend, not the absolute. Both numbers depend entirely on which crawler you're asking. Ahrefs, Moz, Semrush and Majestic will each give you a different count for the same site because each one indexed a different subset of the web. Pick one tool and stay with it, or your own history becomes unreadable.

How many referring domains do you actually need?

There's no universal number, and anyone quoting one is selling something. The answer is always relative to the competition for the specific queries you want.

The method that works:

Search your target keyword.
Take the top five results.
Look up the referring domain count for each of those specific pages — not the whole domain.
That range is your target.

For a low-competition long-tail query, the answer is often surprisingly small — a handful of relevant referring domains and better content than what's ranking. For a commercial head term in a competitive niche, it can be hundreds. How many backlinks you need for SEO works through the calculation in detail.

Quality still sits above both counts

Referring domains is a better metric than backlinks. It's still a count, and a count can't tell you the thing that matters most.

Thirty referring domains that are topically relevant, get real search traffic, and link to you from inside the main body of an article will outperform three hundred from unrelated directories every time. When you're evaluating what you've got, the questions that matter are:

Relevance. Is the linking site about anything close to your subject?
Traffic. Does it get real organic visitors, or does it just have a score?
Placement. Is the link inside real editorial content, or in a footer nobody reads?
Indexation. Is the page the link sits on actually in Google's index?

Those four checks are covered in full in how to vet a link swap partner, and they're the reason growing referring domains deliberately beats growing them fast.

Growing referring domains, specifically

Because the metric counts unique sites, the strategy follows directly: every new link should come from somewhere you haven't been linked from before. Going back to the same three friendly blogs for a fourth, fifth and sixth link adds almost nothing.

That reframes what a good month looks like. Five links from five new domains is a substantially better month than twenty links from two.

It also explains why direct exchange works well for this specific metric — each swap is, by construction, one new referring domain from a site you've been able to inspect first. Backlinkster matches you one-for-one with site owners in related niches, places both links inside real content rather than a footer, and verifies each one live by code, so what you're adding is a genuine new referring domain rather than another repeat.

Frequently asked questions

What's the difference between referring domains and backlinks? Backlinks count every individual link pointing at your site. Referring domains count the unique websites those links come from. One site linking to you 300 times produces 300 backlinks but only one referring domain, and search engines weight the domain count far more heavily.

Is it better to have more backlinks or more referring domains? More referring domains. Links from 100 different sites outperform 1,000 links from 10 sites, because each additional link from a domain you're already linked from adds steeply less value than the first one did.

What is a good backlinks-to-referring-domains ratio? Between 1:1 and 3:1 is the natural editorial pattern. Up to about 10:1 is common and usually harmless. Above roughly 20:1, you almost certainly have site-wide footer, sidebar or blogroll links inflating the count.

Are referring domains the same as linking root domains? Yes — they're the same concept under different vendor names. Moz says "linking root domains," Ahrefs and Semrush say "referring domains." All three mean the count of unique websites linking to you.

Do nofollow links count as referring domains? Most tools count them in the total referring domain figure but let you filter to dofollow only. Ahrefs' Domain Rating specifically uses unique dofollow referring domains. Since 2020 Google treats nofollow as a hint rather than a strict directive, so the distinction is less absolute than it once was — see dofollow vs nofollow links.

Why do Ahrefs and Semrush report different referring domain counts? Because they run separate crawlers with separate indexes. Neither has the whole web, and each finds links the other misses. Differences of 20–40% on the same site are ordinary. Pick one tool for tracking and treat the trend as the signal rather than the absolute number.

The bottom line

Backlinks measure volume; referring domains measure reach. Reach is what search engines are actually trying to assess, and it's the number that tracks with rankings, feeds the authority scores, and resists the inflation that makes raw link counts so easy to misread. Track referring domains, check the ratio when it looks strange, and judge each new domain on relevance and real traffic before you count it as a win.