When a site owner or SEO specialist starts analysing a backlink profile, the same question eventually comes up: which of the linking domains are actually helping, and which ones are quietly causing harm. To answer this, the industry developed several metrics, the most well known being Moz Spam Score and the link toxicity score calculated by various tools. Although these two metrics look similar on the surface, they are built on fundamentally different logic, and misreading them can lead you either to remove perfectly healthy links or to overlook a genuine threat sitting in your profile.
What Moz Spam Score actually measures
Most people treat Moz Spam Score as a simple measure of how spammy a site is, but the real mechanism behind it is far more nuanced. Moz studied millions of domains that had been penalised or dropped from the index and identified several dozen recurring signals. These include domains with very few pages, anchor text that is overly stuffed with keywords, the absence of contact and about pages, certain top-level domain types, missing HTTPS and similar traits. Spam Score expresses, as a percentage, how many of these signals a site exhibits. So a value of 7% does not mean seven dangerous flags were found; it reflects the statistical likelihood that sites with a similar profile have historically been penalised.
This is exactly why Spam Score should never be treated as a final verdict. Moz officially splits the range into relatively low risk from 1% to 30%, moderate risk from 31% to 60%, and high risk from 61% to 100%. In practice experienced specialists treat the 30% threshold as the point where a domain deserves a closer manual look rather than automatic removal. Even highly authoritative news portals can sit around 20-30%, simply because they carry many ad blocks and outbound links, which on its own does not make them spam.
The toxicity metric and how it differs from Spam Score
The toxicity score offered by SEMrush, Ahrefs and other tools works on a different principle. Here each individual link is evaluated and given a score from 0 to 100. SEMrush, for example, relies on more than 45 toxicity markers: very low organic traffic of the linking domain, a structure resembling a link farm or PBN, links placed in comments and forum profiles, hidden or invisible links, and suspicious anchor keywords related to gambling, loans or pharmaceuticals. SEMrush groups toxicity into three bands: 0-44 is low, 45-59 is medium or potentially toxic, and 60-100 is high or toxic.
This difference is easiest to grasp with a concrete example. Imagine 500 domains link to your site. Spam Score tells you how suspicious each of those domains looks overall, but says little about how the link itself was placed. The toxicity metric, by contrast, focuses on the link context: how many other outbound links sit on the same page, whether the anchor looks artificial, and whether the site has any real traffic at all. That is why a professional audit uses both together, Spam Score for judging the general quality of a domain and toxicity for filtering specific links and deciding on each one.
Which numbers are truly dangerous and when to act
The most common mistake is for a specialist to panic the moment they see a high score and start disavowing links in bulk. In reality a single toxic link, or a handful of high Spam Score domains, does not damage an entire profile. Google itself officially states that modern algorithms in most cases simply ignore suspicious links rather than treating them as grounds for a penalty. The real risk appears when a significant share of the profile, for example 20-30% or more of all backlinks, carries a high toxicity score, or when a manual action notice arrives in Search Console.
A practical approach can look like this. First export the entire backlink profile and sort it by toxicity. Pull every link scoring above 60 into a separate list and review each one by hand. More often than not this is where you will find genuine PBN sites, hacked domains or auto-generated spam pages that you really do not want next to your brand. A disavow file should only be prepared for these confirmed, clearly harmful links. The following signs indicate that a link is genuinely toxic:
- The domain has almost zero organic traffic yet thousands of outbound links
- Hundreds of thematically unrelated external links sit on a single page
- The anchor uses commercial or adult keywords with no connection to your brand
- The site has dropped from the index or the domain history changed sharply
Setting tools up correctly and final thoughts
When measuring toxicity it is important to remember that each tool uses its own formula, and the numbers cannot be compared directly. A link scoring 55 in SEMrush may be rated differently in Ahrefs because they assign different weights to the same signals. For this reason a professional audit is best not built on a single tool but on at least two sources combined into one picture before any decision is made. The sayt.uz team, when migrating client sites or moving them into a new hosting environment, recommends running a backlink profile analysis as well, since toxic links left in a domain history can hold back the growth of a new project.
As a closing point it is worth stressing that Spam Score and toxicity scores are a diagnostic instrument, not a verdict. They tell you which side of the profile deserves a deeper look, but the final call should always be made by a human eye that has actually examined the context of each link. A healthy link-building strategy is always aimed at collecting clean, natural and topically relevant backlinks, and with that approach the toxicity problem tends to stay minimal on its own.