Link Spam Score: How Moz Measures Backlink Risk
Spam Score is the inverse of authority — it answers “how likely is this site to get a manual action?” rather than “how much authority does it have?”. Used correctly, it is the cleanest single-number filter for rejecting toxic link sources before they pollute your profile.
What Is Link Spam Score?
Link Spam Score (sometimes called Spam Score) is Moz's percentage-based metric, scored 1% to 100%, that estimates how likely a domain is to be considered spammy based on a basket of 27 flagged signals correlated with sites that have been penalized or banned by Google.
Unlike authority metrics where higher is better, Spam Score is inverted — lower is better. A score under 5% is clean, 5% to 30% is a yellow flag, and anything above 30% should typically be avoided as a link source.
The 27 Spam Flags
Moz computes Spam Score by checking each domain against a catalog of 27 signals that historically correlated with manual actions. You don't need to know all 27, but the highest-impact flags are:
- Low MozTrust or PageRank. The domain has weak trust signals.
- Large site without much link diversity. Many pages, few unique referring IPs.
- Phone number or email in header. Lead-gen-only site pattern.
- Few internal links. Orphaned or thin content network.
- Excessive external outbound links. Link-farm pattern.
- No contact info / privacy policy. Disposable site signal.
- TLD correlated with spammy domains. Some ccTLDs are over-represented in penalized sets.
- Anchor text repetition. Same exact-match anchor used on 90%+ of incoming links.
Spam Score Bands
| Spam Score | Risk Level | Recommended Action |
|---|---|---|
| 1% - 4% | Very low risk | Safe to accept as a link source |
| 5% - 14% | Low risk | Acceptable; check 3-4 spot signals manually |
| 15% - 30% | Moderate risk | Review referring domains carefully before accepting |
| 31% - 60% | High risk | Avoid unless unique strategic value |
| 61% - 100% | Very high risk | Reject; likely already penalized or de-indexed |
What Spam Score Misses
Spam Score is most reliable for clearly-spammy sites and clearly-clean sites. The middle band — the 15% to 30% range — contains a mix of legitimate small businesses (which often trigger lead-gen-related flags) and actual spam. Never automate decisions on this band; review each prospect manually.
When Link Spam Score Matters Most
- Disavow file construction. Domains with 40%+ Spam Score linking to you are top candidates for disavowal.
- Exchange partner screening. Reject any partner whose Spam Score exceeds 25%.
- Backlink audit cleanup. Sort your inbound links by Spam Score to surface the worst-first.
Frequently Asked Questions
Is Link Spam Score the same as Google's spam signals?
No. Spam Score is Moz's third-party estimate. Google has its own spam detection systems that are not publicly documented. Spam Score correlates with what Google penalizes, but it is not a direct readout of Google's internal flags.
Should I disavow every high-spam-score link?
No. Disavow only when there is a clear pattern of low-quality links pointing to your site and you are seeing ranking or traffic decline. Disavowing healthy backlinks based purely on Spam Score is a common rookie mistake that can hurt rankings.
Can a legitimate site have a high Spam Score?
Yes. Small local businesses with thin link profiles, phone numbers in the header, and minimal internal linking often trigger 20%-35% Spam Scores despite being legitimate. Always check the actual site before judging.
How often does Spam Score update?
Moz refreshes Spam Score with each Mozscape index update, which historically happens roughly every 30 days. Recent spam acquisitions can take a full cycle to reflect.
How does PositiveBacklink handle Spam Score?
We screen every exchange partner against a 25% Spam Score ceiling and a Trust Flow / Citation Flow ratio above 0.4, plus our own AI Watchdog signals. Partners that fail any of those filters cannot enter the matching pool.