Site owners often see “backlinks” and “referring domains” beside each other in an SEO tool and treat them as interchangeable. They are not. A backlink is an individual hyperlink pointing to a page. A referring domain is a unique website that contains one or more of those links. One publisher can create many backlinks, while still representing only one referring domain.
That distinction matters because repeated links from one site do not create the same kind of breadth as links from several independent sites. To interpret a profile responsibly, look at the relationship between the two metrics, the quality and relevance of the linking pages, and the pace at which links appear or disappear. This is measurement and diagnosis, not a promise of rankings.
The difference in one example
Imagine a gardening website receives 12 links from three websites. A university horticulture department links to it six times, a specialist nursery links four times, and a local newspaper links twice. The site has 12 backlinks and three referring domains.
The backlink count describes the total observed links. The referring-domain count removes duplicates at the domain level and shows how many distinct sites are willing to cite, mention, or recommend the destination. The same logic applies at page level: if one article receives links from two different domains, it has two referring domains even if one of those domains links to it repeatedly.
Backlinks measure link instances; referring domains measure the number of distinct linking websites behind those instances.
Why unique referring domains add context
Backlinks can be valuable for discovery, referral traffic, and context, but a large total can be misleading when most links come from one source. A sitewide footer link, a set of forum posts, or many links in an archive may increase the count without adding equivalent editorial breadth. The links may still be useful, but the total should not be read as a simple score of trust.
Referring domains provide a different lens. A growing set of relevant, independent publishers can indicate that content is being noticed across a wider part of a topic. It can also expose concentration risk. If a site has 500 backlinks but only four referring domains, a change on one of those sites could affect a large share of the profile. By contrast, 80 backlinks from 40 relevant domains suggests more distribution, although it does not automatically mean the second profile is stronger.
Relevance and editorial context remain essential. A link from a genuinely useful page on a related website deserves closer inspection than a link from an unrelated directory, regardless of the referring domain count. Google’s link guidance also emphasizes crawlable HTML links, descriptive anchor text, and natural context rather than forced keyword repetition. See Google Search Central’s link best practices for the underlying guidance.
What link velocity means
Link velocity is the rate at which a site gains or loses links over a period. You can measure it using new backlinks, new referring domains, lost links, or a combination of these views. For example, a campaign might produce many backlinks from a small number of sites, while a successful piece of news coverage might produce new referring domains across a short period.
Velocity is not a target number that every site should imitate. A sudden increase can be perfectly explainable when a page becomes newsworthy, a product launches, or a useful study is shared. A sudden drop may reflect expired pages, a redesign, a publisher removing old links, or a tool updating its index. The important question is whether the change has a credible explanation and whether the new links are relevant and editorially earned.
Do not confuse a tool’s newly discovered links with links that were necessarily created that week. Third-party crawlers find links at different times, so a chart can reflect discovery as well as acquisition. Compare like-for-like periods, inspect the actual pages, and record both gains and losses. A steady, explainable pattern is more informative than chasing a dramatic spike.
How to interpret both metrics together
1. Check the ratio, then inspect the sources
Divide total backlinks by referring domains only as a prompt for investigation, not as a quality score. A high ratio may be normal for a publication that links to a useful research page from many articles. It may also reflect sitewide templates or duplicated placements. Open a sample of linking pages and ask whether each link has a clear reason to exist.
2. Separate new domains from additional links
When reviewing growth, record how many new referring domains appeared and how many additional backlinks came from domains already known. These are different outcomes. New domains can show broader reach; additional links can show deeper coverage from an existing partner. Both may matter, but they support different conclusions.
3. Review destination pages and anchor text
Identify which pages receive links. A strong homepage count does not tell you whether important product, service, or research pages are discoverable. Also review anchor text for accuracy and variety. Descriptive language helps users understand the destination, while repetitive, manufactured anchors can signal an unnatural promotion pattern. Google recommends concise, relevant anchor text rather than keyword stuffing.
4. Compare relevant competitors carefully
Use the same tool, database, date range, and domain scope when comparing sites. Metrics differ between providers because each maintains its own crawl and calculation methods. A competitor with fewer backlinks may have more relevant referring domains, while a larger site may have links accumulated over many years. For background on the metric behind this site, read what Domain Rating measures and the comparison of Domain Rating and Domain Authority.
A practical review workflow
Start with a baseline date. Note total backlinks, referring domains, followed and nofollowed links where your tool provides those fields, and the main destination pages. Then review recent gains and losses. Classify each meaningful link by topic relevance, page quality, placement, and likely referral value. Finally, write a short explanation for any unusual movement. This turns a dashboard number into an evidence-based record.
For sustainable improvement, focus on publishing something a relevant site would reasonably want to cite: original research, a clear explanation, a useful tool, or a genuinely better resource. Avoid buying links solely to inflate a counter or placing the same link across unrelated sites. The guide to improving Domain Rating sustainably covers the broader principles, while what a backlink is explains the basic link types.
The bottom line
Backlinks tell you how many link instances a tool has found. Referring domains tell you how many distinct websites those links come from. Link velocity adds a time dimension, but it should be interpreted alongside real events, crawler timing, link quality, and losses. Use all three views to ask better questions, not to reduce SEO to a single target.