Domain Authority

Domain Authority important

Domain Authority (DA) is a search engine ranking score developed by Moz that predicts how likely a website is to rank in search engine result pages (SERPs). Domain Authority scores range from one to 100, with higher scores corresponding to a greater likelihood of ranking.

Domain Authority is based on data from our Link Explorer web index and uses dozens of factors in its calculations. The actual Domain Authority calculation itself uses a machine learning model to predictively find a "best fit" algorithm that most closely correlates our link data with rankings across thousands of actual search results that we use as standards to scale against.

Domain Authority is calculated by evaluating multiple factors, including linking root domains and a total number of links, into a single DA score. This score can then be used when comparing websites or tracking the "ranking strength" of a website over time. Domain Authority is not a Google ranking factor and has no effect on the SERPs.

As of the Domain Authority 2.0 update in early 2019, the calculation of a domain's DA score comes from a machine learning algorithm’s predictions about how often Google is using that domain in its search results. If domain A is more likely to appear in a Google SERP than domain B is, then we would expect domain A's DA to be higher than domain B's DA. Learn more about the Domain Authority update and how to discuss it with your team with this presentation or explore how to use DA 2.0 metrics with this comprehensive whitepaper.  

Since DA is based on machine learning calculations, your site's score will often fluctuate as more, fewer, or different data points become available and are incorporated into those calculations. For instance, if facebook.com were to acquire a billion new links, every other site’s DA would drop relative to Facebook’s. Because more established and authoritative domains like Facebook will have increasingly larger link profiles, they take up more of the high-DA slots, leaving less room at the higher end of the scale for other domains with less robust link profiles. Therefore, it's significantly easier to grow your score from 20 to 30 than it is to grow it from 70 to 80. For this reason, it’s important to use Domain Authority as a comparative metric rather than an absolute one.

Because Domain Authority comprises multiple metrics and calculations, pinpointing the exact cause of a change can be a challenge. If your score has gone up or down, there are many potential influencing factors including things like:

• Your link profile growth hasn't yet been captured in our web index.
• The highest-authority sites experienced substantial link growth, skewing the scaling process.
• You earned links from places that don't contribute to Google rankings.
• We crawled (and included in our index) more or fewer of your linking domains than we had in a previous crawl.
• Your Domain Authority is on the lower end of the scoring spectrum and is thus more impacted by scaling fluctuations.
• Your site was affected by the 2019 implementation of Domain Authority 2.0, which caused a 6% average decrease in DA across all websites due to restructuring and improvements to the way DA is calculated.

The key to understanding Domain Authority fluctuations is recognizing that each domain’s score depends on comparison to other domains all across the DA scale, so that even if a website improves its SEO, its Authority score may not always reflect that. Let's look at how "best of" rankings work as a theoretical illustration:

If Singapore has the best air quality in 2020 and then improves it even further in 2021, are they guaranteed to remain at #1 on the best air quality list? What if Denmark also improves its air quality, or what if New Zealand joins the rating system with extremely high air quality in 2021 after having been left out of the rankings in 2020? Maybe the countries ranking 2–10 all improved dramatically and Singapore falls to #11 even though their air got better during that time. Because the scale itself has changed, Singapore's ranking could change independently of any action (or inaction) on their part.

Domain Authority works in a similar fashion. Since it’s based on machine learning and constantly compared against every other website on the scale, after each update, recalculations mean that the score of a given site could go down even if that site has improved its link profile. Such is the nature of a relative, scaled system. Therefore — and this is important enough that we'll emphasize it once more — Authority scores are best viewed as comparative rather than absolute metrics.