SEO Data Bench/Benchmarks/backlink-overlap
Backlink counts across providers: same ranking, different numbers
Twenty vendor domains queried on Serpstat, SE Ranking and Moz on the same day. How far the referring-domain counts diverge, whether the providers at least agree on order, and why authority scores cannot be compared across tools.
Written for people asking: How do I get backlink data without several monthly SEO subscriptions?Why do backlink counts differ between Ahrefs, Semrush, Moz and Serpstat?Which backlink API is cheapest for checking referring domains?
For 20 domains on 15 September 2026, Serpstat, SE Ranking and Moz ranked the domains almost identically by referring domains (Spearman 0.97 to 0.98) while disagreeing on the counts by a median factor of 2.85 and up to 8.6× for one domain. Serpstat reported the lowest count for 19 of 20 domains, typically a third to a half of SE Ranking's or Moz's. Authority scores are on different scales and are not comparable: hunter.io is 60 on Serpstat, 90 on SE Ranking and 60 on Moz. Use any one provider consistently for relative comparisons; do not quote an absolute backlink count as a fact without naming the index.
There is no ground truth for backlinks
Every backlink index is a crawl, and crawls differ in breadth, recency and how they deduplicate. A bigger number is a bigger crawl, not a more correct one. What a buyer can measure is agreement: do the providers rank the same domains in the same order, and how far apart are the absolute counts. This page reports both.
Routes measured: Serpstat, SE Ranking and Moz, one summary call per domain. Ahrefs, Majestic and Semrush could not be called on the run date (plan or credential), so the two indexes most people quote are absent, not scored.
Results by provider
| Provider | Domains returned | Rank correlation, referring domains | p50 | p95 | Cost per domain |
|---|---|---|---|---|---|
| Moz | 20 | 0.97 | 976 ms | 1205 ms | $0.013 |
| SE Ranking | 20 | 0.98 | 1129 ms | 2874 ms | $0.018 |
| Serpstat | 20 | 0.98 | 1026 ms | 1285 ms | $0.0025 |
All three returned a summary for all 20 domains in about a second. The ranking agreement is near perfect: whichever index you use, hunter.io has more referring domains than findymail.com, which has more than icypeas.com.
Results by domain
| Domain | Serpstat | SE Ranking | Moz | Spread |
|---|---|---|---|---|
| hunter.io | 7,628 | 17,504 | 18,011 | 2.4 |
| apollo.io | 8,076 | 25,489 | 23,124 | 3.2 |
| peopledatalabs.com | 482 | 1,457 | 1,663 | 3.5 |
| clay.com | 3,855 | 9,702 | 7,742 | 2.5 |
| explorium.ai | 314 | 1,313 | 1,495 | 4.8 |
| fullenrich.com | 604 | 1,230 | 1,373 | 2.3 |
| findymail.com | 1,479 | 2,701 | 2,788 | 1.9 |
| icypeas.com | 143 | 369 | 384 | 2.7 |
| prospeo.io | 1,605 | 2,976 | 2,966 | 1.9 |
| lusha.com | 2,930 | 10,507 | 8,869 | 3.6 |
| semrush.com | 94,661 | 220,369 | 192,816 | 2.3 |
| ahrefs.com | 69,905 | 156,915 | 133,682 | 2.2 |
| dataforseo.com | 1,435 | 4,301 | 4,646 | 3.2 |
| serpapi.com | 1,581 | 5,318 | 13,627 | 8.6 |
| serpstat.com | 5,447 | 13,627 | 15,127 | 2.8 |
| seranking.com | 11,164 | 22,564 | 23,237 | 2.1 |
| moz.com | 85,388 | 260,201 | 192,877 | 3 |
| apify.com | 4,079 | 16,975 | 11,535 | 4.2 |
| scrapecreators.com | 173 | 476 | 504 | 2.9 |
| treg.to | 15 | 66 | 33 | 4.4 |
Reading the table:
- The median spread is 2.85×. For a typical domain in this cohort, the largest index reports almost three times as many referring domains as the smallest.
- Serpstat is consistently the smallest index here. It reported the lowest count for 19 of 20 domains, usually a third to a half of the other two. That is a crawl-size difference, and it is the reason it is also the cheapest.
- SE Ranking and Moz are close to each other on most domains, but not always: serpapi.com is 5,318 on SE Ranking and 13,627 on Moz, the largest spread in the cohort at 8.6×.
- Small domains have the widest relative spread. treg.to is 15, 66 and 33 referring domains across the three, a 4.4× spread on numbers small enough that a handful of links moves the ratio.
Authority scores are not comparable
Each provider’s authority number is its own model on its own scale. For hunter.io: Serpstat domain rank 60, SE Ranking domain inlink rank 90, Moz domain authority 60. For treg.to: 18, 15 and 9. The scores rank domains similarly but the values mean nothing across tools. Never average them and never quote one as “the” authority.
Who each route fits
- Relative comparisons on a budget: Serpstat at $0.0025 per domain. Its order matches the larger indexes; its counts are smaller.
- Counts closer to the larger commercial indexes: SE Ranking or Moz, at $0.018 and $0.013 per domain.
- You need Ahrefs or Semrush numbers specifically: those require their own plans with API access, which this run did not have.
What this run cannot tell you
Twenty domains from one industry. No time series yet, so freshness (how quickly a new link appears in each index) is not measured. Backlink counts, as opposed to referring domains, are shown in the raw files and diverge far more, because indexes count pages differently. A second dated run is scheduled.
Reproduce it
Cohort, runner and scorer on the dataset page; the 60 raw backlink summaries are under evidence.
Spotted an error or a changed price? Email corrections@seodatabench.com with the page URL and a source. Corrections are logged on the corrections page.