Domain Authority is a scoring system created by Moz to guess how likely a website is to show up on Google. It gives a number between 1 and 100, where higher means better ranking chances. This number comes mostly from how many backlinks a site has and how strong those links are.

It is important to know that Domain Authority is not a Google ranking factor. It is just an outside tool many SEO experts use to check website credibility, link strength, and overall trust.

Different SEO tools like Ahrefs or Semrush have their own authority metrics, but Moz’s DA became the most talked-about term over time. In SEO conversations, people now use “domain authority” even when they mean trust or strength, not only the Moz score.

Historical background of domain authority

The term domain authority came much later, but the concept started with early web search algorithms. Researchers found that links between websites could signal trust, which helped pages rank higher in search engines.

Early link-based authority models

In 1999, computer scientist Jon Kleinberg introduced the HITS algorithm, short for Hyperlink-Induced Topic Search. It identified two key roles online:

• Authorities: trusted web pages linked to often
• Hubs: pages that linked to many authorities

This idea showed how link patterns could reveal which pages were important within a topic.

PageRank and domain trust signals

At the same time, Google created PageRank, a scoring system based on incoming links. If a site got links from trusted sources, its PageRank score improved. This helped its pages rank higher in search engine results.

These methods taught early SEO professionals that link quality and domain strength mattered. Older websites with strong link histories ranked faster than newer ones. People started calling this domain trust or site authority.

Google’s stance on domain authority

Although SEO experts used the term often, Google has clearly said it does not assign any single authority score to domains. Rankings depend on many factors, but not on a universal number like DA.

Domain Authority as a named metric

Moz later turned this idea into a measurable number called Domain Authority. The tool used link signals to predict a site’s chance of ranking. Over time, many SEO platforms built similar domain-level metrics, but Moz’s DA became the most widely known.

How Moz calculates Domain Authority

Moz Domain Authority is a ranking score developed by Moz in the mid-2000s. It gives websites a score from 1 to 100 to show their potential to rank in search engines, based mainly on backlink data and domain-level SEO signals.

Scoring model and scale

The Domain Authority score is based on a logarithmic scale, not a straight one. This means going from DA 20 to 30 is easier than going from DA 70 to 80. Very few websites ever reach the top range. Big media sites like Forbes or Wikipedia may show DA above 90, while small or new sites often stay in single digits.

Factors used in the DA algorithm

Moz calculates DA using many link-related factors, including:

• Linking root domains (how many different websites link to yours)
• Total backlinks
• Quality of linking pages
• Spam Score, which tracks low-quality or risky links
• Link position, such as how far the link is from the homepage

These signals help Moz estimate how trusted or powerful a domain looks in comparison to others.

The DA 2.0 update

In 2019, Moz upgraded the DA algorithm with machine learning and a neural network model. This version, known as DA 2.0, better reflects what real ranking patterns look like in Google. It discounts spammy or artificial links more accurately and adapts to Google algorithm changes over time.

Relative, not absolute value

One important point is that Domain Authority is a relative metric. A site’s DA can change even if nothing on the site has changed. This is because DA reflects how a site ranks among others in Moz’s own index. If other websites gain better links, your DA might drop in comparison.

There is no fixed number that defines a “good” DA. What matters is whether your DA is higher than your competitors in your niche.

Domain vs Page Authority

Moz also gives a separate score called Page Authority (PA). While Domain Authority is for the whole domain, PA predicts the ranking power of a single page. Both are used by SEOs to measure visibility and strength.

Tools to check Domain Authority

Moz offers different tools to view Domain Authority:

• Link Explorer
• MozBar browser extension
• Domain Authority Checker

These tools show your DA score along with stats like referring domains, spam score, and ranking keywords.

Example: A Moz report for Forbes.com might show DA 94, over 1.5 million linking domains, and a 1 percent spam score. This points to strong backlink quality and wide search visibility.

Use of DA in SEO strategy

Moz reminds users that DA is not a Google ranking factor. It is best used as a comparison tool, not a final verdict. A site with DA 50 can beat a site with DA 60 for some keywords if its content is more relevant or its on-page SEO is stronger.

SEO experts often track DA scores to watch progress, benchmark competitors, or measure link-building impact. Still, they combine it with other signals like keyword rankings, organic traffic, and content quality.

How other tools measure domain-level authority

After Moz launched Domain Authority, other SEO platforms introduced their own versions to measure domain strength and link credibility. While these scores work in a similar way, each provider uses its own crawler, ranking model, and data scale.

Common authority metrics across SEO tools

Several major providers now offer domain-level authority scores:

• Ahrefs Domain Rating (DR)
• SEMrush Authority Score (AS)
• Majestic Trust Flow (TF) and Citation Flow (CF)

Each of these is used widely in SEO, especially for link building, competitive analysis, and domain comparison.

Key differences among scoring systems

Metric	Provider	Introduced	Scale
Moz Domain Authority (DA)	Moz	2004	1 to 100
Majestic Trust Flow (TF)	Majestic	2012	0 to 100
Ahrefs Domain Rating (DR)	Ahrefs	2016	0 to 100
SEMrush Authority Score (AS)	SEMrush	2018	0 to 100

Not used in Google rankings

It is important to note that none of these metrics come from Google. They are third-party tools. Search engines do not use them for ranking websites.

Still, SEO professionals rely on these scores to check domain credibility, assess link power, and compare websites in a competitive space. These tools are often part of daily SEO workflows.

How Ahrefs measures domain Rating

Domain Rating (DR) is a proprietary score created by Ahrefs to show the backlink strength of a full domain. It is measured on a 0 to 100 scale, where higher DR usually means stronger link authority and better chance of ranking.

Link quality and referring domains

Ahrefs looks at both the number and quality of websites linking to a domain. A few key points include:

• Referring domains matter more than raw backlinks.
• Links from high-DR sites pass more strength, or link juice.
• But that strength is shared if the linking site also links to many others.

Example: A link from a DR 80 site that links to 3,000 domains may carry less weight than a DR 30 site linking to just 20. This system prevents one powerful site from unfairly boosting thousands of others.

Ahrefs combines these signals into a raw link strength number, then scales it to fit the 0–100 DR range.

DR as a relative metric

Like Moz’s DA, Domain Rating is not absolute. It depends on what other domains look like in Ahrefs’ own index. A domain can lose DR even if its own links stay the same, simply because many other sites improved their link profiles.

That is why a good DR score depends on context. In one niche, DR 30 might be strong. In another, DR 60 could be average.

Role in SEO and link building

DR is widely used for:

• Backlink prospecting
• Competitor comparison
• Judging domain-level authority for outreach

Still, Ahrefs makes it clear: do not judge a website by DR alone. You should also check:

• Relevance of the linking content
• Organic traffic patterns
• Spam signals or unnatural links

Ahrefs also offers a URL Rating (UR), which scores the strength of individual pages. In some cases, UR can align better with Google rankings than DR.

How SEMrush calculates Authority Score

Authority Score is SEMrush’s version of a domain authority score, shown on a scale from 0 to 100. It is not based on links alone. The score combines link power, organic traffic, and spam checks to give a wider picture of a domain’s SEO strength.

Link power from backlinks

Like other metrics such as DA and DR, SEMrush checks:

• Number of referring domains
• Quality of those domains
• Backlink variety and strength

These signals together form the link power value. This part looks at how trusted and well-connected the domain is across the web.

Organic traffic data

SEMrush adds a second layer: estimated traffic from Google search. This part of the score reflects how well the domain actually performs in organic search results. A site with strong backlinks but no traffic may still score lower than a site with fewer links but higher search visibility.

Natural link profile and spam signals

SEMrush also scans for spam factors. These help catch fake or unnatural link patterns, such as:

• Too many dofollow links with very few nofollow
• High backlinks but low organic traffic
• Many links from domains on the same IP network
• Duplicate or mirrored link profiles

These patterns can suggest link manipulation or use of Private Blog Networks (PBNs).

Overall score and SEO usage

SEMrush combines all three factors — link power, organic traffic, and spam checks — into one single score. A high Authority Score means a site has strong backlinks, real search traffic, and no red flags.

SEOs often use this score to:

• Spot low-quality domains that may look strong due to fake links
• Choose better link building targets
• Track domain growth or compare against competitors

Like other metrics, Authority Score changes over time. SEMrush updates the algorithm regularly. Sudden drops or gains can reflect changes in traffic, backlinks, or how the score is calculated.

Measuring authority with Majestic Flow Metrics

Trust Flow and Citation Flow are two scoring systems from Majestic that help evaluate a domain’s link quality and link quantity. Together, they are known as Flow Metrics, and both use a 0 to 100 scale.

Citation Flow: measuring link quantity

Citation Flow (CF) measures how many backlinks point to a domain or page. It does not check the quality of those links. A site with many backlinks will have a higher CF, even if some links come from spammy or low-trust sources.

This score reflects link volume or influence, not trust.

Trust Flow: measuring link quality

Trust Flow (TF) checks how close a domain is to trusted seed sites in Majestic’s index. If a site is directly or indirectly linked to by many authoritative websites, it will have a higher TF. This score shows the trustworthiness of a backlink profile.

TF is based on the idea that links from trusted sites carry more weight, while links from shady or low-value domains do not add trust.

Interpreting CF and TF together

Majestic suggests looking at both scores together:

• A site with high CF and low TF may have many links but from poor sources — often seen as a spam warning.
• A strong, healthy site usually has a TF that is closer to its CF.
• Rarely, some academic or trusted government sites may have TF higher than CF, which signals very high-quality backlinks with fewer total links.

In general, TF is lower than CF for most websites, because almost every site picks up some low-value links from the web.

Practical use in SEO

Flow Metrics help SEOs:

• Evaluate backlink quality
• Spot spammy domains
• Compare competitor link profiles
• Choose link building targets

When checking a possible backlink, SEOs often look at the TF/CF ratio of the linking site. A balanced or trust-leaning ratio is considered a safer, more reliable link source.

Like DA and DR, TF and CF are not part of Google’s ranking algorithm. These are third-party signals, useful for site audits and competitor comparisons, not for predicting exact rankings.

Use of domain authority metrics in SEO

Domain Authority and similar metrics are used in everyday SEO work to estimate a site’s ranking strength and link quality. These third-party scores help guide strategy, but they do not directly affect search engine results.

Competitor analysis

SEOs often compare DA, DR, or Authority Score to measure how strong a site is versus its competitors. A higher score usually means a stronger backlink profile. This helps professionals:

• Judge how hard it will be to outrank a competitor
• Find link gaps by spotting sites that link to top-ranking competitors
• Choose targets for backlink outreach

Link building and evaluation

When choosing where to get links from, SEOs check a domain’s authority score as a signal of quality. A link from a site with high DA or DR is seen as more valuable.

These scores are also used to:

• Spot harmful backlinks with very low Trust Flow or similar spam indicators
• Disavow low-quality links during clean-up audits
• Prioritize high-value backlinks for retention or outreach

Tracking SEO progress

Website owners and agencies often track Domain Authority over time to watch general SEO growth. If DA is going up, it usually means:

• The site is gaining better backlinks
• Content is getting more visibility
• The site is performing well relative to others in the same niche

However, small drops or spikes are common. Since DA is relative, your score can change even if your backlinks stay the same, especially after index updates or algorithm changes in tools like Moz or Ahrefs.

Client reports and site valuation

Many agencies include DA or Authority Score in client reports because it is a simple, visible number. In sales, a site with DA 80 may be seen as more valuable than one with DA 20. This affects:

• Ad pricing
• Website sales
• Brand trust signals

Still, SEO experts warn against focusing too much on any one score.Known limitations and Google’s position

Authority scores are not used by Google. They are made by third-party tools. Google’s engineers, including John Mueller, have confirmed that Domain Authority is not a ranking factor.

Google looks at many signals on a page-by-page basis. A high-DA site can still have low-ranking pages if the content is weak. A low-DA site can still rank well if the content is useful and well-linked.

When authority metrics mislead

Authority scores can sometimes create confusion:

• A drop in DA might just mean Moz’s index changed, not your backlink profile
• A moderate DA site can outrank a high-DA site if its content is more relevant or better optimized

That is why SEOs use these metrics as guides, not rules. Real SEO success depends on many things: relevance, user experience, on-page SEO, and content quality — not just a domain score.

Common criticisms of domain authority scores

While widely used, domain authority metrics often face criticism for being misunderstood, limited, or open to misuse. These scores are helpful, but they are not official or complete measures of SEO strength.

Not part of Google’s ranking system

Many beginners wrongly believe that Domain Authority or similar scores are used by Google. In truth, DA, DR, TF, and others are created by third-party tools like Moz, Ahrefs, SEMrush, and Majestic.

Google has publicly stated that it does not use a sitewide authority score in its ranking system. Google’s algorithm uses many signals, mostly at the page level, including content relevance, link quality, and user signals, not a fixed score for each domain.

Potential for manipulation

Authority scores depend heavily on backlink data, which can be manipulated. Some SEOs have boosted DA or DR by:

• Buying large numbers of backlinks
• Using Private Blog Networks (PBNs)
• Redirecting expired domains
• Posting spammy blog comments

In one case, a brand-new site with no content reached DA 52 through purchased links alone. SEO tools have since improved their systems to detect such tactics. For example:

• Moz added a Spam Score
• SEMrush checks unnatural link patterns
• Majestic separates link trust from volume

Still, no tool is perfect, and some fake metrics can go unnoticed. SEOs are advised to check other signals, like traffic, content quality, and topical relevance, not just DA or DR.

Only shows part of SEO

Domain authority scores mostly reflect link profiles, not the full SEO picture. They do not measure:

• Content quality
• Relevance to search queries
• Page speed or technical SEO
• User experience or engagement

A site with high DA may still rank poorly if the content is weak or outdated. Meanwhile, a low-DA site with helpful content may rank well for specific keywords.

Over-focusing on DA can lead to missed opportunities, like ignoring smaller sites that are highly relevant or trusted in a niche. Today’s SEO best practices include E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness), and only some of that overlaps with backlink-based scores.

Differences between tools

Each tool uses different algorithms, data sources, and index sizes. This means:

• A domain might show DA 65 in Moz but low Trust Flow in Majestic
• Ahrefs and SEMrush might give different scores for the same site
• A spammy domain might go undetected by one tool but flagged by another

For this reason, SEOs often compare multiple metrics together. If DA, DR, TF, and Authority Score all agree, the site is likely strong. If they do not, it’s worth looking deeper into its backlink sources and content.

Final considerations

Domain Authority scores are useful tools for:

• Competitive analysis
• Link building
• SEO progress tracking

But they are not guarantees of success. Real ranking gains come from:

• Creating valuable, original content
• Earning natural backlinks
• Offering good user experience
• Maintaining technical health

Focusing only on authority scores can create false confidence or concern. They should be used in context, with other SEO signals. A rise or fall in DA alone does not confirm success or failure in search.