Domain authority, DA, is a proprietary metric developed by Moz that predicts how likely a domain is to rank in search engine results pages based primarily on the strength and quality of its backlink profile. Scored on a logarithmic scale from 1 to 100 domain authority provides a single number that represents the accumulated link-based ranking power of an entire domain, a proxy for the SEO equity that the domain has built through its history of content, links, and online presence.

The higher a domain’s authority score the more likely its pages are, all else being equal, to rank competitively in search results. A domain with DA 80 has accumulated significantly more link-based authority than a domain with DA 30, and that accumulated authority benefits every page on the higher-DA domain through the internal distribution of PageRank.

Domain authority is not a Google metric, it is a third-party calculation by Moz based on their own link index and their interpretation of the factors that influence Google rankings. Google does not use Moz’s domain authority in its ranking algorithms. However domain authority and equivalent metrics from other tools, Domain Rating from Ahrefs, Authority Score from Semrush, have become standard reference points in SEO practice because they correlate reasonably well with actual ranking performance and provide useful comparative benchmarks when evaluating link building opportunities and competitive positioning.

How domain authority is calculated

Moz calculates domain authority using a machine learning model trained to correlate with Google search rankings. The model takes multiple inputs, primarily backlink data from Moz’s link index, and outputs a predicted ranking likelihood score.

Linking root domains: the number of unique root domains linking to the site. Links from 1,000 different domains contribute more authority than 1,000 links from the same domain. Diversity of linking domains is one of the most important factors in domain authority calculation, a signal that many different sites independently find the content valuable.

Link quality: not all linking domains contribute equally. Links from high-authority domains, major publications, government sites, educational institutions, established industry authorities, contribute more authority than links from low-authority or newly created domains. The quality weighting means a site with 100 links from high-authority domains may have higher DA than a site with 1,000 links from low-quality sources.

Link spam signals: links from manipulative, spammy, or artificial sources reduce rather than increase domain authority. Moz’s model attempts to identify and discount link spam, links that exist specifically to manipulate rankings rather than as genuine editorial endorsements.

Overall link ecosystem: because domain authority is a relative metric, scored against all other domains in Moz’s index, changes in other domains’ authority affect a domain’s score even without changes to the domain itself. A domain that acquires no new links may see its DA decrease if other domains in the same competitive space are actively building links, its relative position in the ecosystem has weakened even without any action on its own link profile.

Logarithmic scale: domain authority uses a logarithmic scale, a domain moving from DA 20 to DA 30 requires significantly less link acquisition than moving from DA 70 to DA 80. The higher the existing authority the more difficult it becomes to improve the score because the marginal impact of each new link decreases as the baseline grows stronger.

Domain authority vs other authority metrics

Several SEO tools offer their own domain-level authority metrics, each calculated differently using different link indexes and different methodologies. Understanding the differences helps use these metrics appropriately.

Moz Domain Authority, DA: the original and most widely referenced domain authority metric. Calculated from Moz’s link index. Uses a 1-100 logarithmic scale. Updated regularly as Moz’s link crawl discovers new links and loses track of removed links. The metric that gave the concept its name, “domain authority” is now used generically to refer to any domain-level authority score though technically it refers specifically to Moz’s metric.

Ahrefs Domain Rating, DR: Ahrefs’ domain-level authority metric. Calculated from Ahrefs’ link index, one of the largest and most frequently updated link indexes in the SEO industry. Also uses a 1-100 logarithmic scale. DR focuses primarily on the number and quality of linking domains rather than individual links. Because Ahrefs’ link index is comprehensive DR is widely considered a reliable authority metric.

Semrush Authority Score, AS: Semrush’s domain-level authority metric. Calculated from Semrush’s link index combined with organic traffic data and other signals. Uses a 1-100 scale. The inclusion of traffic signals alongside link data means AS reflects a slightly broader assessment of domain authority than pure link-based metrics.

Majestic Trust Flow and Citation Flow: Majestic’s dual metrics provide complementary views of link authority. Citation Flow measures link quantity, how many links point to the domain. Trust Flow measures link quality, how trustworthy the linking sites are based on their proximity to a seed set of trusted sites. The ratio of Trust Flow to Citation Flow provides a quality signal, high Trust Flow relative to Citation Flow indicates a clean, high-quality link profile.

Key principle, use multiple metrics: no single authority metric is definitive. Each tool uses a different link index, some links in Ahrefs may not be in Moz’s index and vice versa. Each uses different calculation methodologies. Using multiple authority metrics provides a more complete picture than relying on any single metric. Consistent signals across multiple tools, a domain with high DA, high DR, and high AS, provide stronger confidence than a high score in only one metric.

What domain authority measures, and what it does not

Understanding domain authority’s scope and limitations prevents misuse and misinterpretation.

What DA measures: the accumulated link-based authority of an entire domain as estimated by Moz’s model. DA reflects historical link building efforts, the quality and quantity of backlinks pointing to any page across the entire domain. A high DA indicates a domain that many authoritative sites have chosen to link to over time.

What DA does not measure: individual page quality. A high-DA domain can have individual pages that rank poorly because their content is thin, irrelevant to query intent, or poorly optimised. Domain authority is a domain-level signal, it does not guarantee that any specific page will rank well. Page-level authority, URL Rating in Ahrefs, Page Authority in Moz, measures the link-based authority of individual pages rather than the whole domain.

DA is not a Google metric: Google does not use Moz’s domain authority score in its ranking algorithms. Google’s internal authority calculations, descendants of PageRank: are proprietary and different from any third-party metric. High Moz DA does not guarantee Google rankings, it correlates with ranking performance because both reflect the same underlying reality of link quality and quantity, but the correlation is imperfect.

DA fluctuates with the ecosystem: because DA is a relative metric changes in the broader link ecosystem affect individual domain scores. A site that makes no changes and acquires no links may see its DA change, up or down, as other domains’ link profiles evolve. DA fluctuations do not always reflect changes in the site’s own link profile.

DA does not reflect content quality: a domain can have high DA from historical link building while currently publishing poor content. DA reflects past link acquisition, not current content quality. Google’s ranking systems evaluate content quality and helpfulness independently of link-based signals, a high-DA domain that publishes low-quality content will not rank as well as a high-DA domain with high-quality content.

Domain authority and redirect management

Domain authority intersects with redirect management in several practical ways, understanding these connections informs strategic decisions about domain acquisitions, migrations, and redirect portfolio management.

Expired domain acquisition informed by DA: domain authority metrics are the primary tool for evaluating expired domain acquisitions. An expired domain with high DA has accumulated a strong backlink profile, configuring a 301 redirect from the expired domain to a primary domain transfers some of the DA-generating backlink equity to the primary domain. DA provides a quick first-pass assessment of acquisition value, domains with meaningful DA from quality linking root domains merit deeper due diligence.

Redirect destination authority improvement: the fundamental goal of domain consolidation redirects is to increase the authority of the primary destination domain by concentrating the backlink profiles of multiple redirected domains. Monitoring the primary domain’s DA before and after consolidation reveals whether the expected authority improvement is materialising, though the full effect may take months to be reflected in DA calculations as Moz’s model processes the redirect signals.

Competitive analysis with DA: domain authority is widely used for competitive analysis, comparing a site’s DA against competitors to assess relative link-based authority positioning. A site with significantly lower DA than its competitors faces a link authority gap that may need to be addressed through link building to achieve competitive rankings. Understanding the authority gap informs realistic expectations for how long and how much link building effort is needed to compete effectively.

Link building target assessment: DA is a standard metric for evaluating potential link building targets. A backlink from a DA 80 site contributes substantially more authority than a backlink from a DA 15 site. When evaluating whether to pursue a link building opportunity, whether through content, digital PR, or other methods, the target site’s DA provides a quick proxy for the likely authority value of a successfully acquired link.

Domain parking value assessment: brand protection domains and parked domains that are being redirected to a primary domain may accumulate backlinks over time, increasing their DA. Monitoring DA for redirect source domains reveals whether they are accumulating authority that is being transferred to the primary domain through the redirect, confirming the ongoing value of maintaining the redirect portfolio.

Improving domain authority

Building domain authority is a long-term effort, the logarithmic scale and relative nature of the metric mean that authority improvements require sustained, quality link acquisition over time.

Earning high-quality backlinks: the most direct path to higher domain authority. Links from high-DA sites with relevant content pointing to the domain are the primary driver of authority improvement. Strategies for earning high-quality links include publishing genuinely valuable, linkable content, comprehensive guides, original research, data-driven analyses, that other sites reference and link to naturally. Digital PR, creating newsworthy content that earns coverage and links from news publications. Building relationships with industry publications, bloggers, and authoritative sites in the niche.

Fixing broken backlinks: backlinks pointing to broken URLs on a site, returning 404 errors: are wasting their authority contribution. Identifying broken backlinks through backlink analysis tools and configuring 301 redirects from the broken URLs to relevant live pages recovers the authority from these links, improving effective DA without acquiring new links.

Removing or disavowing toxic links: links from spammy, manipulative, or irrelevant sources can drag down domain authority if they trigger spam signals in Moz’s model. Identifying and disavowing toxic links through Google’s disavow tool, and ensuring Moz’s SpamScore is low, maintains a clean link profile that maximises authority calculation.

Internal link optimisation: while domain authority reflects external backlinks the distribution of authority within the site through internal links affects page-level authority. Optimising internal linking, ensuring important pages receive more internal links from high-authority pages, improves the practical benefit of the domain’s accumulated authority for specific pages.

Patience and consistency: domain authority improvements do not happen overnight. The logarithmic scale means each incremental DA point becomes harder to achieve as authority grows. Consistent, long-term link building and content investment produces sustained authority growth, short-term tactics rarely produce meaningful or lasting DA improvements.

Common domain authority misconceptions

DA is a Google ranking factor: the most persistent misconception. Moz’s domain authority is not used by Google. Optimising specifically for DA rather than for the underlying link quality signals that both DA and Google measure is a misaligned effort. Build links that genuinely improve the site’s authority profile, DA improvement follows as a byproduct.

High DA guarantees rankings: domain authority predicts ranking potential but does not guarantee rankings for any specific query. Content quality, page-level authority, technical SEO, and many other factors alongside domain authority determine whether a specific page ranks for a specific query.

DA changes immediately reflect link changes: domain authority updates are not real-time. Moz’s link index is crawled continuously but DA calculations are updated on a schedule. A new high-quality backlink acquired today may not be reflected in the DA score for weeks. The delay is normal, DA reflects historical accumulated authority rather than a real-time link count.

DA scores are comparable across tools: a DA of 50 from Moz is not equivalent to a DR of 50 from Ahrefs or an Authority Score of 50 from Semrush. Each tool uses different link indexes and different calculation methodologies, scores are only comparable within the same tool’s ecosystem, not across tools.