What are Semrush Subdomain Backlinks? Here’s What I Found

Why Subdomains Even Get Their Own Backlink Data

A subdomain — think shop.example.com or help.example.com — technically sits under your root domain, but search engines and SEO tools have historically treated it as its own entity for authority purposes. That’s been debated for years (Google has said subdomains aren’t automatically siloed anymore), but in practical SEO tool reporting, the separation still exists and still matters.

Semrush’s Backlinks tool respects this. When you type in a full domain, you get the aggregate — every backlink pointing anywhere on that domain, subdomains included. When you type in just the subdomain, Semrush filters everything down to links pointing at that specific piece of the site.

I’ve run into this constantly when auditing client sites that have a separate blog. or shop. Subdomain sitting on a different CMS than the main site. The backlink profile of the subdomain often looks nothing like the main domain’s — sometimes stronger, sometimes almost empty — and if you don’t check it separately, you get a misleading picture of the site’s overall link equity.

How to Actually Pull Subdomain Backlink Data in Semrush

The mechanics are simple, but the interpretation is where people go wrong.

Step one — go to the Backlinks tool and enter the subdomain exactly as it appears (including the “www” or absence of it, if relevant). Semrush treats blog.example.com and example.com as separate search inputs.

Step two — check the search type toggle. Semrush lets you choose between root domain, subdomain-only, or exact URL scope. Picking “subdomain” here is what actually isolates the data — skip this, and you’ll pull the wrong set without realizing it.

Step three — use the Backlinks Overview report to compare up to five subdomains side by side. This is useful if you’re running multiple subdomains (a blog, a docs site, a store) and want to see which one is actually earning links.

In my testing across client projects with multi-subdomain setups, this comparison view is where I usually find the biggest surprise — a “secondary” subdomain, like a help center or resource hub, often turns out to be pulling in more referring domains than the main site because it’s the part people actually link to when citing information.

What the Backlink Data Actually Tells You

A subdomain backlink report isn’t just a bigger or smaller number than your main domain — it tells you something structural about where your link equity is concentrated.

A few things worth checking specifically:

• Referring domains, not just total backlinks. A subdomain with 40 backlinks from 3 sites tells a different story than one with 40 backlinks from 35 sites.
• Anchor text patterns. Subdomains built for specific content (documentation, a knowledge base, a careers page) tend to attract very topic-specific anchor text, which can actually help topical relevance if that subdomain content is closely tied to your core business.
• Authority Score comparison. Semrush assigns an Authority Score at both the root and subdomain levels. If your subdomain’s score is meaningfully lower than your root domain’s, that’s often a sign it’s been neglected in outreach or internal linking.

One thing people frequently miss: if you’re planning to migrate a subdomain into a subfolder (a common move for consolidating SEO authority), checking the subdomain’s existing backlink profile first tells you exactly what you stand to gain — or what redirects you need to get right so that link equity doesn’t get lost in the move.

Where This Trips People Up

A few mistakes I see repeatedly when reviewing audits:

Treating subdomain and root domain authority as interchangeable. They’re not. A domain with strong root authority can have a nearly empty subdomain, and vice versa.

Forgetting the search scope toggle. If you search a subdomain without switching Semrush to subdomain-only mode, you may still be pulling root-inclusive data without realizing it — which defeats the entire point of isolating the analysis.

Ignoring subdomains when doing competitor research. If a competitor runs a resource hub or blog on a subdomain, their backlink strategy for that content often looks completely different from their main site’s link-building approach. Missing that means missing half their strategy.

A Quick Note on Backlink Tools Beyond Just This Check

Subdomain-level analysis is one small piece of what a proper backlink audit involves — figuring out toxic links, disavow candidates, and link gap opportunities against competitors takes broader tooling. If you’re new to this side of Semrush entirely, it’s worth first getting comfortable with how to use Semrush for free before diving into the more advanced backlink comparison features.

And if you’re deciding whether Semrush’s backlink depth is worth the subscription compared to alternatives, it’s a fair question — tools like Ahrefs are often mentioned in the same breath. Worth reading Semrush vs Ahrefs if that’s the comparison you’re actually trying to make.

If you want to test this yourself before committing, Semrush currently offers a 7-day free trial — plenty of time to pull backlink reports for your own subdomains and see what’s actually going on under the hood.