Moz Domain Authority vs Semrush Authority Score: Which to Trust?

Moz Domain Authority (DA) and Semrush Authority Score (AS) both rate websites on a 0-100 scale, but they use different data and algorithms. Comparing them directly leads to confusion.

For the full picture of how all three major metrics compare (including Ahrefs DR), see our DA vs DR vs Authority Score comparison.

Sources:

• Moz: What is Domain Authority and how it works
• Semrush: Authority Score components and methodology

How Moz Domain Authority works#

Domain Authority was created by Moz in 2010 and has become the most widely referenced domain metric in SEO discussions.

How it is calculated:

• Moz crawls the web with its own bot (Rogerbot) and builds a link index
• DA uses a machine learning model trained on real Google search results
• The model weighs 40+ factors, primarily link-based signals
• The score predicts how likely a domain is to rank — not how high

Key characteristics:

• Scale: 1-100 (logarithmic — going from 20 to 30 is easier than 70 to 80)
• Primary factor: Linking root domains (unique sites pointing to you)
• Secondary factors: Total backlinks, link quality, MozRank, MozTrust
• Update frequency: Periodic (can take weeks between updates)
• Index size: Smaller than Ahrefs or Semrush

Strengths: Well-established metric with a long history. Widely recognized in the SEO industry. Good for competitive benchmarking when everyone uses the same tool.

Limitations: Smaller crawl index means it may miss links that Ahrefs or Semrush detect. Slower update cycle means recent link changes take time to reflect.

Source: Moz: Domain Authority methodology and factors

How Semrush Authority Score works#

Authority Score is Semrush's composite metric introduced to give a single-number health check for any domain.

How it is calculated:

Semrush combines three components:

1. Link Power (backlinks): Quality and quantity of referring domains, backlink types, follow vs nofollow ratio
2. Organic Traffic: Estimated monthly visitors from organic search, based on keyword rankings and estimated CTR
3. Spam Signals: Indicators that a domain might be unnatural or manipulative — penalizes spammy profiles

Key characteristics:

• Scale: 0-100
• Primary factors: Backlinks + organic traffic + spam detection (three-pronged)
• Update frequency: Moderate (more frequent than Moz)
• Index size: Large (43 trillion+ backlinks claimed)
• Scope: Works at both domain and URL level

Strengths: Incorporates organic traffic, not just links — gives a more holistic view. Spam detection penalizes artificially inflated profiles. Larger index than Moz.

Limitations: The traffic component means a site with great backlinks but low traffic gets a lower score. The composite nature makes it harder to diagnose what exactly is driving the score up or down.

Source: Semrush: Authority Score methodology and components

Side-by-side comparison#

Example: same site, different scores#

It is common to see a site with DA 35 and AS 45, or DA 50 and AS 30. This is not a bug — it reflects the different methodologies:

• A site with strong backlinks but low organic traffic will have a higher DA than AS (because DA does not factor in traffic)
• A site with moderate backlinks but high organic traffic will have a higher AS than DA (because AS rewards traffic)
• A site with many spammy backlinks will have a lower AS than DA (because AS has explicit spam detection)

Why the same site gets different scores#

There are four main reasons:

1. Different data inputs#

Moz uses only link data. Semrush uses links + traffic + spam signals. A site that ranks well with few links will score higher in Semrush than Moz.

2. Different crawl indexes#

Moz and Semrush maintain separate web crawlers. They discover different links. A link that Semrush has indexed but Moz has not will only affect the Semrush score.

3. Different algorithms#

Moz trains a machine learning model on actual Google search results. Semrush uses a weighted composite formula. Even with the same input data, the math produces different outputs.

4. Different update schedules#

Moz updates DA on a slower cycle. Semrush updates more frequently. If you recently gained or lost links, Semrush may reflect the change before Moz does.

Which to use and when#

Use Moz DA when:#

• You are doing competitive analysis within the Moz ecosystem
• You want a link-focused metric that ignores traffic
• You are communicating with clients or partners who know DA (it is the most recognized metric)
• You want historical comparison — DA has been around since 2010

Use Semrush AS when:#

• You want a holistic score that factors in traffic, not just links
• You need spam detection to evaluate link prospects
• You are already working in the Semrush platform
• You want both domain-level and URL-level scores

Use both when:#

• You are evaluating link opportunities and want a cross-reference
• A site has a suspiciously high score in one tool — check the other for a sanity check
• You are building a backlink prospect list and want to filter by multiple quality signals

Where Ahrefs Domain Rating fits in#

Ahrefs Domain Rating (DR) is the third major metric. It focuses purely on backlink profile strength — specifically the number and quality of referring domains and how link equity flows between them.

For the detailed comparison between all three, see our DA vs DR comparison guide. To learn how to check all three scores, see our domain authority checking guide.

FAQs#

Is Moz DA or Semrush AS more accurate?#

Neither is "more accurate" because they measure different things. DA is a link-based ranking prediction. AS is a composite health score. Choose based on what question you are trying to answer: link strength (DA) or overall domain health (AS).

Why is my Semrush Authority Score higher than my Moz DA?#

Likely because your site has strong organic traffic. Semrush factors in traffic alongside links, so sites with good rankings but a modest link profile will score higher in Semrush.

Why is my Moz DA higher than my Semrush Authority Score?#

Likely because your site has a strong backlink profile but Semrush's spam detection flagged some links, or your organic traffic is lower than expected for your link count.

Can I improve both scores at the same time?#

Yes. Building quality backlinks, publishing strong content, and fixing technical SEO improves both DA and AS. The specific activities are the same — the scores just weight them differently.

Which score do clients expect to see?#

Moz DA is the most widely recognized metric in the SEO industry. If you are reporting to clients who are not deeply technical, DA is the safest choice because it is the most familiar term.

How often do these scores update?#

Moz DA updates on a periodic cycle, typically every few weeks. Semrush AS updates more frequently but not in real-time. Check monthly for meaningful trend data rather than watching for daily changes.