Domain Authority (DA) is a search engine ranking score developed by Moz that predicts how well a website will rank on search engine result pages (SERPs). A Domain Authority score ranges from one to 100, with higher scores corresponding to a greater ability to rank.
Domain Authority is calculated by evaluating linking root domains, number of total links, MozRank, MozTrust, etc. — into a single DA score. This score can then be used when comparing websites or tracking the “ranking strength” of a website over time.
You can view a website’s DA by using MozBar (a free Chrome-extension), Open Site Explorer (a backlink analysis tool), the SERP Analysis section of Keyword Explorer, and dozens of other SEO tools across the web.
How is Domain Authority scored?
We score Domain Authority on a 100-point, logarithmic scale based on a website’s popularity, MozRank, MozTrust, etc. Thus, it’s significantly easier to grow your score from 20 to 30 than it is to grow from 70 to 80.
What is a “good” Domain Authority?
Generally speaking, sites with a very large number of high-quality external links (such as Wikipedia or Google.com) are at the top end of the Domain Authority scale, whereas small businesses and websites with fewer inbound links may have a much lower DA score. Brand new websites will always start with a Domain Authority score of one.
Because of how Domain Authority is calculated (see “Technical definition of Domain Authority” below), it’s best used as a comparative metric (rather than an absolute, concrete score) when doing research in the search results and determining which sites may have more powerful/important link profiles than others. Because it’s a comparative tool, there isn’t necessarily a “good” or “bad” Domain Authority score.
Domain Authority vs. Page Authority
Whereas Domain Authority measures the predictive ranking strength of entire domains or subdomains, Page Authority measures the strength of individual pages.
Where can you find Domain Authority?
Domain Authority metrics are incorporated into dozens of SEO and online marketing platforms across the web.
In the Moz ecosystem, you can measure Domain Authority using Open Site Explorer, MozBar (Moz’s free SEO toolbar), or in the SERP Analysis section of Keyword Explorer. Authority metrics are also incorporated into all Moz Pro campaigns, as well as the Mozscape API.
Technical definition of Domain Authority
Domain Authority is based on data from the Mozscape web index and includes link counts, MozRank and MozTrust scores, and dozens of other factors (more than 40 in total). The actual Domain Authority calculation itself uses a machine learning model to predictively find a “best fit” algorithm that most closely correlates Mozscape data with rankings across thousands of actual search results that we use as standards to scale against.
While specific metrics like MozRank can answer questions of raw link popularity (i.e. link equity), and link counts can show the raw quantities of linking pages/sites, Domain Authority (and Page Authority) metrics address the higher level question of a domain (or page’s) “rankability.”
Since Authority is based on machine learning calculations, your site’s score will often fluctuate as more, less, or different data points are used in the calculation — for instance, when a new Mozscape web index is released. For this reason, keep in mind that it’s best to use Domain Authority as a relative metric to compare against the link profiles of other sites as opposed to an absolute value “scoring” the efficacy of your internal SEO efforts.
How do I influence Domain Authority?
Domain Authority is difficult to influence directly. It is made up of an aggregate of other metrics (MozRank, MozTrust, link profile, and more) that each have an impact on the authority score. This was done intentionally; this metric is meant to approximate how competitive a given site is in Google search results. Since Google takes a lot of factors into account, a metric that tries to calculate it must incorporate a lot of factors as well.
The best way to influence the Domain Authority metric is to improve your overall SEO. In particular, you should focus on your link profile — which influences MozRank and MozTrust — by getting more links from other well-linked-to pages.
Why did my Authority change?
Because Domain Authority (and, for that matter, Page Authority) is comprised of 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 was too recent and hasn’t yet been captured in the Mozscape web index. (It can take several index update cycles for newly acquired links to be included.)
The highest-authority sites experienced substantial link growth, skewing the scaling process.
You earned links from places that don’t contribute to Google ranking.
We crawled (and included in our index) more or fewer of your linking domains than we had previously.
Your domain authority is on the lower end of the scoring spectrum and is thus more impacted by scaling fluctuation.
You can read more about how to interpret these (and other) fluctuations in Authority scores here.
The key to understanding Page and Domain Authority fluctuations is that these metrics don’t exist in a vacuum — they depend on many positive and negative factors so that even if a given site improves its SEO, its Authority score(s) may not always reflect it. A good metaphor to help understand why is how “best of” rankings work. Let’s look at an example:
If Singapore has the best air quality in 2015, and improves it even further in 2016, are they guaranteed to remain at #1? What if Denmark also improves its air quality, or New Zealand (which, say, had been left out of the rankings in 2015) joins the rating system? Maybe countries 2-10 all improved dramatically and Singapore has now fallen to #11, even though they technically got better, not worse. Because there are many other factors at play, Singapore’s ranking could change in spite of any action (or inaction) whatsoever on their part.
Domain Authority (and Page Authority) work in a similar fashion. Since they’re scaled on a 100-point system, after each update, the recalculations mean that Authority score of a given page/site could go down even if that page/site has improved their link quantity and quality. Such is the nature of a relative, scaled system. As such — and this is important enough that we’ll emphasize it once more — Authority scores are best viewed as comparative rather than absolute metrics.