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How is Domain Authority calculated: The 6 Moz algorithm inputs, machine-learning model, and DA 2.0 retraining cadence
Domain Authority is calculated by Moz using a machine-learning model that combines 6 link-graph signals into a single logarithmic score from 1 to 100.
The 6 algorithm inputs are linking root domains, MozRank, MozTrust, Spam Score adjustment, anchor text distribution, and total backlink volume.
Moz trains the model against actual SERP rankings the Mozscape crawler observes across the public web; the model output approximates how the link graph predicts ranking strength relative to other domains.
The DA 2.0 algorithm pivot in March 2019 retrained the model on Spam Score-aware features and introduced a near-monthly index refresh cadence.
SEO Domains operates the curated marketplace with a 220,000+ pre-screened catalogue from $100 entry-level domains through $1.5 million premium acquisitions; every listing surfaces the Domain Authority value alongside the underlying link-profile signals so buyers verify the calculation inputs before acquisition.
How is Domain Authority calculated: the 6 Moz algorithm inputs
Domain Authority is calculated by feeding 6 link-graph signals into a Moz machine-learning model that outputs a single logarithmic score from 1 to 100.
The model is trained against actual SERP outcomes the Mozscape crawler observes across the public web.
The output approximates relative ranking strength. A DA 60 site outranks a DA 30 site at a higher rate than the reverse when other factors are held equal.
The 6 inputs combine three signal families:
- Volume signals: linking root domains and total backlinks.
- Authority signals: MozRank and MozTrust.
- Adjustment signals: Spam Score and anchor distribution.
Moz publishes the 6 inputs in the Mozscape API documentation.
The 6 algorithm inputs are documented in the Mozscape API reference and the Moz Link Explorer feature descriptions. Brian Dean at Backlinko has covered the 6-input model across link-building case studies through 2018-2024.
The Moz blog publishes algorithm-update notes on the Help Hub when the model is retrained. The DA 2.0 March 2019 pivot is the latest major retraining.
The model output approximates rather than predicts ranking position.
Domain Authority does not predict the SERP position of any specific URL on any specific query. The model output approximates relative link-graph strength across domains.
A DA 60 site outranks a DA 30 site at a higher rate. The actual SERP position depends on hundreds of additional ranking factors the Moz model does not measure:
- Content relevance and query intent.
- Freshness and on-page optimisation.
- Schema markup and page speed.
- Dwell time signals.
Input 1: Linking root domains, the primary volume signal
Linking root domains is the count of unique referring domains pointing at the target domain and carries the dominant weight in the Domain Authority calculation.
A site with 1,000 linking root domains outranks a site with 100 linking root domains on the DA scale even when total backlink count is similar.
The primary volume signal explains 60-70 percent of the variance in DA across the Mozscape index when controlling for Spam Score and anchor distribution.
Linking root domains carries dominant weight because unique sources outrank repeated sources.
Google’s link-graph weighting treats a single link from each of 100 unique domains as stronger than 100 links from 1 domain. The Moz machine-learning model mirrors that weighting.
Authority Hacker has documented the linking-root-domain dominance in link-building case studies through 2020-2024 across affiliate and content sites moving from DA 10 to DA 50.
The linking-root-domain count reaches DA 30 at roughly 300 unique referring domains.
The 300-linking-root-domain milestone reflects 3-6 months of structured outreach campaigns at editorial conversion rates of 5-10 percent.
Sites running 4-6 active outreach workstreams in parallel reach the milestone within the standard new-site ramp window. Aged-domain acquisition skips the outreach phase entirely by inheriting an established linking-root-domain base from the previous registrant.
Input 2: MozRank, the page-level link authority weighting
MozRank is the Moz-equivalent of Google’s PageRank: a 0-10 logarithmic score that weights each link by the authority of its source page.
A link from a MozRank 8 page passes substantially more authority than a link from a MozRank 3 page.
The Domain Authority model aggregates MozRank values across the link profile to produce the page-level authority component of the DA score.
MozRank scales logarithmically from 0 to 10 mirroring the original PageRank scale.
MozRank 6 is roughly 10 times stronger than MozRank 5. MozRank 7 is roughly 10 times stronger than MozRank 6.
The logarithmic scale matches the original PageRank scale published in the 1998 Brin-Page paper.
Moz designed MozRank to approximate the public PageRank Google deprecated in 2016 after the toolbar value lost its update cadence.
High-MozRank sources include enterprise media domains and established editorial publications.
The MozRank 7-9 range concentrates at three source tiers:
- Top-tier publications such as The New York Times, Forbes, and BBC.
- Enterprise brands such as Microsoft and IBM.
- Established educational and government domains.
Glen Allsopp at Detailed has documented the high-MozRank tier in enterprise SEO programme audits. A single link from this tier moves the DA needle more than 50 links from MozRank 2-3 sources combined.
Input 3: MozTrust, the trust-seed proximity signal
MozTrust measures how close the target domain sits to a curated set of trusted seed domains in the Moz link graph. The trust seed set includes three source types:
- Government domains.
- Established educational institutions.
- Editorially-vetted publishers.
Domains with shorter link-path distance to the trust seeds accumulate higher MozTrust scores.
The trust dimension prevents pure-volume link profiles from inflating Domain Authority without authentic editorial validation.
MozTrust uses link-path distance to differentiate authentic from manipulated link profiles.
Two domains with similar linking-root-domain counts can have substantially different MozTrust scores depending on the trust-seed proximity of their referring sources.
A domain linked from .gov and .edu sources within 2-3 link hops accumulates higher MozTrust than a domain linked exclusively from low-trust commercial sites at 5-6 hop distance.
The mechanism is the Moz adaptation of the trust-flow concept Majestic uses on the TrustFlow metric.
Charles Floate has documented the MozTrust signal across PBN A/B testing through 2018-2024.
The Charles Floate PBN audits track MozTrust changes alongside DA shifts when manipulative link profiles are detected.
The pattern is consistent. Manipulated profiles inflate DA temporarily through volume tactics. MozTrust resists the inflation because the trust-seed proximity does not change.
The DA correction follows in subsequent algorithm refreshes when the Spam Score adjustment compounds.
Input 4: Spam Score adjustment, the penalty layer
Spam Score is the Moz penalty layer that adjusts the Domain Authority score downward when the link profile triggers manipulation flags. Moz tracks 27 spam signals across on-page, link-profile, and domain-registration patterns.
The Spam Score expresses the percentage of those flags the domain triggers. The higher the Spam Score, the larger the negative adjustment to the calculated DA.
| Category | Example flags | DA adjustment impact |
|---|---|---|
| Link-profile flags | Excessive same-anchor links, suspicious referring TLD ratio, low referring-domain diversity | Strongest negative adjustment |
| Domain-level flags | Short domain length, numerical TLD pattern, WHOIS privacy | Moderate negative adjustment |
| On-page flags | Thin content patterns, excessive external linking, missing trust signals | Lighter negative adjustment |
| Reputation flags | Email blacklist presence, historical penalty signals | Compounding negative adjustment |
The Spam Score adjustment is the DA 2.0 retraining’s headline change.
The DA 2.0 March 2019 retraining shifted Spam Score from a separate diagnostic metric to an integrated input in the DA calculation.
Before DA 2.0, manipulated profiles inflated DA without proportional Spam Score consequences. After DA 2.0, the Spam Score adjustment is baked into the calculation.
The Charles Floate PBN A/B tests across 2019-2020 documented the DA drop pattern on manipulated profiles after the pivot.
Input 5: Anchor text distribution, the manipulation detection input
Anchor text distribution measures the diversity and natural pattern of the anchor text in the link profile.
A natural link profile shows a mix of branded anchors, naked URLs, generic anchors ("click here", "read more"), and a minority of exact-match commercial anchors.
A manipulated profile concentrates exact-match commercial anchors that signal anchor-text gaming.
The Domain Authority model penalises the manipulated distribution through reduced effective contribution from the linking root domain count.
Natural anchor distributions split into 4 categories with predictable proportions.
The standard natural distribution splits into four proportions:
- Branded anchors: 40-60 percent of total.
- Naked URLs and generic anchors: 30-40 percent.
- Exact-match commercial anchors: 5-15 percent.
- Miscellaneous topical anchors: 10-20 percent.
Matt Diggity at Authority Builders has documented the safe-anchor distribution across affiliate-site audits through 2019-2024.
Profiles exceeding 30 percent exact-match commercial anchors trigger the anchor-distribution manipulation flag.
Cyrus Shepard at Zyppy has cross-validated the anchor distribution signal in correlation studies.
The Cyrus Shepard Zyppy research through 2022-2024 cross-validates the anchor-distribution input against ranking-correlation data.
The correlation pattern is consistent. Domains with natural anchor distributions outrank domains with manipulated distributions when other inputs are equal.
The signal is the Moz model’s primary defence against pure-volume link-building tactics.
DA 2.0 retraining cadence: the March 2019 algorithm pivot
DA 2.0 is the March 2019 Moz retraining of the Domain Authority machine-learning model that integrated Spam Score as a calculation input and introduced near-monthly index refresh cadence.
The pivot is the headline change to the Domain Authority calculation since the 2012 launch.
Sites with clean link profiles saw modest DA changes after DA 2.0. Sites with manipulated profiles saw DA drops of 15-25 points as the Spam Score adjustment compounded.
The near-monthly cadence is slower than Ahrefs Domain Rating refreshes.
Ahrefs Domain Rating refreshes the link-graph index continuously through near-real-time crawling, so DR updates within hours of link gains or losses.
Moz Domain Authority refreshes on a ~30-day cycle, so DA reflects link-profile changes a month after they happen.
Aged-domain buyers reading DA at the marketplace verify the Mozscape index date alongside the current DA value to confirm freshness.
5 frequently asked questions about how Domain Authority is calculated
The 5 top questions practitioners and aged-domain buyers ask about how Moz calculates Domain Authority. Answers reflect the documented Mozscape methodology alongside SEO industry interpretation.
Q1Which input carries the highest weight in the Domain Authority calculation?
Linking root domains carries the dominant weight. It explains 60-70 percent of DA variance across the Mozscape index when controlling for Spam Score and anchor distribution.
Practitioners optimising for DA prioritise unique-referring-domain acquisition over total backlink volume because the linking-root-domain input dominates the model output.
Q2At what cadence does Moz recalculate Domain Authority?
Moz refreshes the Mozscape link-graph index approximately every 30 days. The DA recalculation runs end-to-end on the same cycle.
Sites adding links between index refreshes see the DA update reflected at the next refresh, not in near-real-time. The cadence is slower than the Ahrefs Domain Rating continuous-refresh cycle.
Q3Does Google use Domain Authority as a ranking factor?
Domain Authority is a third-party predictive proxy calculated by Moz on the Mozscape link graph. Google does not use Moz Domain Authority directly in its ranking algorithm.
The metric approximates how the link graph correlates with ranking outcomes. Practitioners use DA as a comparative reference, not as a Google ranking factor.
Q4What is DA 2.0 and how does it differ from the original Domain Authority calculation?
DA 2.0 is the March 2019 Moz retraining of the Domain Authority machine-learning model. The pivot integrated Spam Score as a calculation input and introduced near-monthly index refresh cadence.
The Spam Score integration produced DA drops of 15-25 points on manipulated profiles while leaving clean profiles substantially unchanged.
Q5Can a domain’s DA calculation be manipulated?
Pure-volume manipulation tactics (mass-link blasts, exact-match anchor stuffing) trigger Spam Score flags that reduce the calculated DA after the DA 2.0 retraining.
The anchor distribution input and Spam Score adjustment penalty layer make sustained manipulation detectable within 1-2 index refresh cycles. Charles Floate has documented the detection pattern across PBN A/B audits.
How aged-domain buyers read Domain Authority calculation at the marketplace
Aged-domain buyers reading Domain Authority at the marketplace verify all 6 calculation inputs, not the headline DA value in isolation.
A DA 45 site with strong linking root domains and clean Spam Score is a different acquisition target than a DA 45 site inflated by anchor-text gaming. The inflated site heads for DA correction at the next index refresh.
The SEO Domains catalogue surfaces the underlying inputs at the listing level so buyers verify the calculation foundation before acquisition.
| Verification step | Catalogue signal | Acquisition gate |
|---|---|---|
| Linking root domain count | Listed alongside DA value on every listing | LRD count must support the DA tier per the 6-input model |
| Spam Score | Listed as percentage and adjustment magnitude | Spam Score under 5 percent passes screening; 5-15 percent requires review |
| Anchor text diversity | Top-anchor distribution surfaced in the inheritance report | Branded anchors dominate; exact-match commercial under 15 percent |
| MozTrust proximity | Trust-seed proximity flagged when below threshold | MozTrust within 1 standard deviation of DA tier baseline |
The catalogue 7-vector inheritance screen audits the calculation inputs at inventory ingestion.
SEO Domains operates a 7-vector inheritance screen across the 220,000+ catalogue. The screen evaluates the DA calculation inputs alongside Domain Rating, Trust Flow, Citation Flow, and Spam Score before listings reach buyers.
Constantin Oesterling has documented the same multi-input screening discipline across guest-posting authority audits through 2021-2024.
ICANN-accredited transfer preserves the DA calculation foundation through ownership change.
SEO Domains operates with ICANN-accredited registrar transfer protocols. The Mozscape link-graph index records link profiles by hostname and propagates the established DA calculation inputs to the new owner.
The 6 inputs (linking root domains, MozRank, MozTrust, Spam Score, anchor distribution, total backlinks) transfer with the domain because the Mozscape crawler indexes the link profile by URL, not by registrant identity.
