In SEO, not all links are created equal. Two of the most commonly measured metrics, backlinks and referring domains, are often used interchangeably, yet they represent very different things. Backlinks reflect link volume, while referring domains reflect breadth and diversity. Both can influence rankings, but the balance between them is what truly determines a site’s authority in search.
Marketers who understand how these metrics interact can build smarter, more sustainable link building campaigns. Let’s explore what sets them apart, how Google evaluates them, and how businesses can optimize for both.
Backlinks vs Referring Domains: Understanding the Basics
At the simplest level:
- A backlink is a hyperlink from one web page to another. If a blog post links to your site five times, you’ve gained five backlinks.
- A referring domain is the unique website that backlink comes from. In the above case, it’s still just one referring domain, regardless of link count.
The distinction matters because Google doesn’t view five links from one site the same as five links from five different sites. Think of it like recommendations: getting praised multiple times by the same friend is nice, but being vouched for by many different people carries more weight.
SEO professionals often evaluate both metrics during a backlink audit, since a healthy profile balances quantity with domain diversity.
Why Domain Diversity Signals Real Authority
Google places strong emphasis on referring domain diversity because it reflects trust across the web.
If your website has 5,000 backlinks from just three domains, the search engine might interpret that as manipulative, or at least as an unbalanced profile. But if those same 5,000 backlinks come from 500 unique domains, it paints a picture of broad credibility.
For example, imagine a SaaS startup. If all their links come from partner companies’ blogs, Google sees a narrow trust circle. But if they also appear on industry news outlets, SaaS review platforms, educational resources, and discussion forums, the algorithm recognizes a much wider vote of confidence. That’s why many effective SaaS link building strategies are designed specifically to maximize referring domain variety.
This is also why PR-driven link building has become more valuable: a single earned mention on a high-authority news domain often carries more SEO weight than dozens of repetitive links from small blogs.
When Backlink Quantity Still Makes an Impact
Although domain diversity is critical, there are situations where link volume plays an important role.
For instance, suppose your site earns coverage on a high-authority publication like Forbes. That one domain may generate dozens of backlinks over time — in news articles, contributor columns, and syndicated content. Even though it’s the same referring domain, the cumulative link equity passed to your site can still significantly improve rankings.
Similarly, backlinks concentrated on a single content hub can reinforce topical relevance. If an eCommerce store gets multiple contextual backlinks from a cluster of product review sites, Google may interpret that as strong topical authority.
This is why SEOs don’t dismiss backlink quantity outright. Instead, they monitor anchor text variety, distribution patterns, and placement to ensure those links add value rather than look spammy.
How Google Balances the Two Metrics
Google doesn’t publish a direct formula for how it weighs backlinks versus referring domains, but decades of SEO testing show a clear pattern:
- Referring domains are a stronger trust signal.
- Backlink volume amplifies that signal, but only when links come from credible, contextually relevant sources.
- Low-quality bulk links (thousands of backlinks from a few weak sites) provide little benefit and may even harm visibility.
A well-rounded link profile has both: diverse referring domains that act as “roots,” and multiple backlinks from those domains that act as reinforcing “branches.”
One reason link diversity carries more weight today is Google’s ongoing fight against spam. In the early 2010s, some websites ranked with massive link farms generating thousands of backlinks from the same few domains. Today, search algorithms are far more sophisticated, penalizing manipulation while rewarding authentic, editorially given links.
Building a Strategy That Balances Volume and Diversity
The most effective SEO campaigns don’t ask which metric is more important but instead focus on how to balance both. Some practical approaches include:
- Prioritize new referring domains first. Aim for a steady inflow of unique domains each month. Outreach to industry blogs, niche directories, podcasts, and associations helps broaden your base and ensures your site is recognized in multiple digital spaces. Over time, this creates a stronger foundation that can’t be replicated by competitors chasing sheer link numbers.
- Reinforce existing domains with quality backlinks. Once you’ve secured coverage, look for opportunities to deepen authority through additional mentions, case studies, or content partnerships on those same sites. These repeat signals demonstrate to Google that the relationship is ongoing and that your content continues to earn attention, not just a one-off placement.
- Leverage content formats that attract both. Original research, tools, and in-depth guides tend to attract links from many different domains, while ongoing PR and content syndication naturally build backlink volume. The key is to consistently produce assets that are valuable enough to earn both new attention and repeated mentions from trusted publishers.
For small businesses and startups, this often means beginning with scalable outreach and affordable link building strategies, then expanding into higher-budget PR campaigns once domain diversity is established. Over time, this layered approach builds a resilient link profile that supports both near-term ranking improvements and long-term SEO growth.
The Risks of Focusing Too Narrowly
Over-optimizing for either backlinks or referring domains can backfire:
- Chasing backlink quantity only can lead to spammy link profiles filled with low-value guest posts or forum links. Not only do these links contribute little to no ranking power, but they may also invite manual penalties or algorithmic filters that suppress visibility.
- Chasing domain diversity only without reinforcement can result in “thin” authority, where no single domain contributes enough strength to significantly impact rankings. This often leads to fragmented link equity and makes it harder to compete in industries where competitors have both diverse and deep link relationships.
That’s why a nuanced approach — supported by regular audits and quality checks — is essential. Identifying toxic or irrelevant links with specialized broken backlink checkers also ensures your profile remains healthy over time. Regular monitoring helps you avoid building strategies that look good on paper but fail to drive real search engine performance.
Tracking and Measuring the Right Way
Knowing whether your strategy is balanced requires the right tools.
- Ahrefs, SEMrush, and Moz provide detailed reports on backlink numbers, referring domains, and anchor text ratios.
- Google Search Console shows confirmed backlinks directly from Google’s perspective.
- Link monitoring tools help detect lost or broken backlinks, so you can reclaim link equity instead of letting it fade.
But tools alone aren’t enough. The data has to be interpreted in context. For example, 1,000 backlinks from 50 domains may look impressive, but if half of those domains are irrelevant or spammy, the real SEO benefit could be minimal. That’s why many businesses turn to specialized link building services, not just for execution, but for expert analysis of what the numbers actually mean.
Final Thoughts: Quality + Diversity = Long-Term Success
The debate between backlinks and referring domains is not about choosing one over the other. Instead, it’s about recognizing how the two work together:
- Referring domains show the breadth of trust across the web.
- Backlinks strengthen that trust when distributed intelligently.
- Google rewards profiles that balance both — diverse yet reinforced, credible yet scalable.
For marketers, the takeaway is clear: don’t obsess over sheer numbers. Focus on building meaningful, diverse relationships across your niche, while also nurturing deeper links from those relationships over time.If you’re ready to strengthen your SEO performance with a strategy that balances both backlink volume and domain diversity, Novo Marketing’s link building services are designed to deliver sustainable, measurable growth.