No one can say for sure how big the internet is, but we know it’s prodigious. There are:

  • Nearly 2 billion live websites.
  • More than 100 trillion total web pages.
  • At least 2.5 quintillion bytes of data added to it daily.
  • An incalculably vast number of links between pages.

For context, NASA estimates that there are 250 billion stars in the Milky Way galaxy. The scale of the internet is best described as cosmic.

If the internet is its own universe, Google is its most prolific voyager. The search engine crawls the web’s expanse 40,000 times per second. Each time, it returns with links to what it believes are the most authoritative sources of content for a search query.

So, is your site a beacon of authority that will light up searchers’ paths to knowledge, or a mote of dust whose content is bound to dwell in the deepest recesses of search engine results pages (SERPs)?

There’s no way of knowing for sure. But Domain Authority may just be the closest you can come to an answer.


Table of Contents

Chapter 1: Understanding Domain Authority
Chapter 2: Measuring Domain Authority
Chapter 3: Links and Domain Authority
Chapter 4: Search engine optimization and Domain Authority
Chapter 5: Why Domain Authority changes
Conclusion: Backlink building never stops


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Chapter 1: Understanding Domain Authority

1. What is Domain Authority (DA)?

Domain Authority is a metric created by Moz that tries to predict how well a website is expected to rank in SERPs, with 0 being the lowest probability of ranking well, and 100 being the highest. Domain authority is ranked on a logarithmic score, meaning it’s harder to increase your score from 60 to 70 than it would be to raise it from 30 to 40.

2. How does Moz determine DA?

Mainly through an analysis of proprietary metrics. These include, but definitely aren’t limited to:

  • Linking root domains (number of unique backlinks to your site).
  • Total number of inbound links to your site.
  • Spam score, or a measure of the level of “spamminess” of sites that link to your site.

3. What is DA 2.0?

Domain Authority 2.0, released in 2019, is an updated version of DA 1.0. It analyzes a much larger library of links (35.5 trillion). Moz has also switched to a neural model that can better detect link manipulation. In essence, there’s more data being analyzed in a more nuanced way to improve the accuracy of the score.

Domain Authority 2.0 – Moz

4. Is DA a ranking factor?

No – it’s a metric made by Moz. Google has nothing to do with DA, and DA in no way influences whether or not your site will rank.

5. Why does DA matter?

Even though it’s not a ranking factor, it’s the closest thing we have to a metric that attempts to predict how well a site will rank. Experts have been known to spar over the accuracy of the metric – meaning, is it an accurate prediction?

The jury is still out on that one, but the general consensus is that DA is nonetheless valuable for link building purposes. Search engines favor sites with links from authoritative sources, and DA is a fairly reliable metric for determining what qualifies as “an authoritative source” in Google’s eyes.

6. Does DA accurately predict how my site will rank?

We haven’t seen definitive proof that it does (see question 5).

7. How is DA different from PageRank?

PageRank was basically Google’s now-defunct version of DA. It ranked a site’s authority on a scale of 1 to 10, and was shut down in 2016.

8. How is DA different from Page Authority?

Domain authority predicts how well domains and subdomains rank, whereas page authority is a Moz metric that estimates how well a single page on a particular site will rank.

9. Are there any similar metrics to DA worth measuring?

Quite a few, actually. None use the exact same factors to reach a score, but some examples of metrics that attempt to quantify “trustworthiness” and “authority” include the following:

  • SEMrush’s Authority Score.
  • Ahrefs’ Domain Rating.
  • Majestic SEO’s Trust Flow and Citation Flow.

Domain Rating from Ahrefs

Check Domain Rating on Ahrefs through the Site Explorer tool.


SEMrush Authority Score

Check Authority Score in SEMrush’s Backlink Analytics tool.

Domain Authority is arguably the most comprehensive in terms of the number of links analyzed, but we have yet to encounter hard evidence revealing as much.

10. Can sites with low DA outrank sites with high DA?

Absolutely. Microsoft.com, for example, will probably never outrank Brafton for a keyword like “Persona Examples” or “B2B Content Marketing.” The authority of a site, as determined by the quality and quantity of backlinks, is an important factor – whether you call it by DA or any other name. But it’s hardly the only factor.

Chapter 2: Measuring Domain Authority

1. What is a good DA score?

Domain authority is best used as a relative metric that is gauged against your competitors’ DA scores. For example a DA score of 60 is good if your competitors average a 50. For context, brand new sites start with a DA score of 1. Only a few major sites such as Facebook, Amazon and YouTube have DA scores at or near 100.

2. How do you check DA score?

You can check any site’s DA score for free by installing the MozBar Chrome extension. You can also check DA through one of Moz’s paid tools like Moz Keyword Explorer and Link Explorer.

3. How often does your DA score change?

Moz updates your DA score daily. However, it takes a lot to noticeably move the needle. Drastic changes to your DA score may stem from an update from Moz. Most updates from Moz are fairly minor (every 3-4 weeks) and usually will not have a pronounced impact on your score.

Chapter 3: Links and Domain Authority

1. What is a backlink profile?

A backlink profile, or backlink portfolio, is your total collection of backlinks, also known as inbound links or incoming links. The definition doesn’t implicitly distinguish unique backlinks from total number of backlinks.

However, most website analytics tools can do that for you. For instance, SEMrush has metrics for “Total Backlinks” for the collective number of inbound links and “Referring Domains” to show the unique sources of those backlinks.

Moz authority score

2. Why is a backlink profile so important to DA?

Because the number of backlinks and where those backlinks come from weigh heavily into Moz’s DA score. Moz cares because Google and Bing care. Search engines look at backlinks as a sort of reputational barometer. Credible sites linking to your domain are votes of confidence. Few or questionable sites linking to your domain could be red flags.

3. What are ‘good’ backlinks?

Basically, any “follow” links to your website that come from a site with a DA score that is higher or comparable to yours. More simply, any backlink to your site from a popular, trustworthy domain is a good link.

A “follow” link is any link that does not have the rel=”nofollow” tag. For instance, if an industry magazine links to your site in the body of an article, that would be a follow link. It’s an organic vote of confidence for your site, and it will pass along good “link juice.”

A no-follow link is any user-generated link in the comments section, links in the source section of Wikipedia, links from paid ads and paid search, and links on social media. The nofollow tag exists to prevent spammers on comment boards and social media channels from exploiting the benefits of backlinking.

4. Are ‘nofollow’ links bad news?

Not necessarily. They do not pass along link equity in the way that a follow link might, which means they won’t directly build DA. However, Moz has suggested that nofollow links can have some value when they appear on credible sites. Research conducted by Backlinko also indicates as much.

Using Occam’s Razor, we can also discern that nofollow links have value if they’re generating traffic – for instance, they’re being clicked on in Facebook posts and Yelp comments. Long story short, nofollow links don’t build DA, but can have some search engine optimization (SEO) value.

5. So what are ‘bad links’ and how can they negatively impact your DA?

Links from sites that have low DA or low trust scores (identifiable through Moz and other tools). Moz factors its “Spam Score” – which is based on analysis of 27 features that are known to appear on banned or penalized sites – into link quality, which, in turn, negatively influences DA.

6. How do “root domains” tie into domain authority?

Root domain refers to the highest level of your site’s structure. For instance, “Yourwebsite.com” might be your root domain. Within that domain, you might have a specific page (“Yourwebsite.com/blog”).

A subdomain can also exist as part of your root domain, and can have a completely separate DA score from your root domain. An example of a subdomain might be “Shopping.Yourwebsite.com.”

7. How do social media links affect DA?

Some sources suggest that social signals do influence DA – though these could be cases of correlation and not causation.

What we do know for certain, though, is that when links are well-shared on social media, they generate more traffic, and this visibility increases the chances that authoritative sources will organically link back to that content.

8. Does internal linking influence DA?

No. However, it can help pass authority from one page on your site to another.

Chapter 4: Search engine optimization and Domain Authority

1. How does content relate to DA?

For starters, you need content because you have to give other sites something to link back to. That content also has to be good enough and well-promoted enough to actually have a chance of earning backlinks.

Otherwise, Moz has not explicitly stated that it uses high-quality content as a factor in determining DA. But they have implied that great content can ultimately help individual pages rank better on Google, which in turn attracts more backlinks that will directly improve DA.

Remember: DA is an overall domain metric that tries to project how well your overall website will rank on search, not an individual web page. If you can get multiple web pages to rank well on Google, you can improve DA, and those improvements – in theory – should correlate to ranking improvements across your entire site.

2. How can search engine optimization (SEO) improve your DA?

Again, it may seem counter-intuitive, but DA is not meant to score the effectiveness of your SEO strategy.

That said, SEO tactics can be responsible for why certain sites have strong backlink portfolios and others don’t. As mentioned, getting more individual pages on search results and ranking for keywords improves the chances of your content being found via search, and that boosts the likelihood that you’ll earn quality backlinks.

3. How does domain authority help/harm ranking for target keywords?

Sites with higher DA scores have a better chance of ranking for keywords with high difficulty scores. Consider targeting keywords with difficulty scores that are within 10 points of your DA score. This is a type of off-page SEO that can have huge benefits on your site’s overall ranking on search.

4. What’s the relationship between guest blogging and DA?

Blogging on someone else’s website or contributing content to an online magazine are some of the easiest ways to earn high-quality backlinks that improve DA – assuming that site’s DA score is comparable to, or higher than, your own.

Chapter 5: Why Domain Authority changes

1. Why does your DA change?

Finally, we arrive at the titular question – and we saved it for last for a reason. You’ll need a strong understanding on what DA is and how it’s determined to understand how it changes.

And DA can change for multiple reasons:

  1. Updates to how Moz determines DA.
  2. Because DA is a relative metric, meaning the sites with the highest DA have a score of 100. If one of those sites experiences substantial link growth (as happens from time to time with say, Facebook and Twitter), the entire scale gets skewed, and this can influence your DA, particularly if it’s at the lower end.
  3. Your backlink portfolio changes – purposeful or incidental, and for better or for worse.

2. What can I do about it?

Try to figure out the reason behind the change. This isn’t always possible, but there are a few places to look.

First, did Moz upgrade? Look at their “What’s New” page to find out if that’s the reason for the change, and try to get to the root of why that upgrade may have positively or negatively affected you.

In the event that you’ve noticed your DA increase – and you’ve ruled out an algorithm change – the first place to go is your backlink portfolio. If it has grown, identify which new referring domains have the best DA, what content they’re linking to and how most users are discovering those pages (social media, direct linking traffic from a few particularly popular web pages, search, etc.).

The goal is to figure out what you’re doing right and do more of it.

If your DA has gone down – and it’s not an algorithm change – again, look at your backlink profile.

It’s possible it hasn’t experienced any growth. Ideally, your number of backlinks should always be climbing since, on the whole, more links are added to the web each day than removed – meaning, for the most part, the DA scale is always trending upward. Put differently, more backlinks on the web at large suggest that the standard for “authority” is always increasing.

Also try to identify toxic links – those links from sites with malware or adware, from spam sites, link networks that exist solely for link-building purposes, etc. These can be identified using an SEO tool like SEMrush. Alternatively, if you’re using Moz tools, toxic links should reflect in your overall Spam Score.

Either way, you need to identify toxic links, and then disavow them through Google Support. Just follow the directions on this page.

Otherwise, look for erroneous page redirects, 404 errors and other broken links on your site that could be hurting your DA.

Conclusion: Backlink building never stops

And if it does, that’s a huge neon sign in Google’s eyes that your domain is becoming less relevant to searchers.

Think of your backlink portfolio as a building that should always be getting taller. If it stops growing, it begins to fall behind the other buildings that are still growing. And when this happens, it will almost certainly begin to get pushed down toward the bottom of the biggest, most densely populated digital metropolis of all: SERPs.

Domain authority estimates how tall your building is relative to the buildings around it, so to speak. And yes, it’s a correlative estimate. But it’s one of the best we have.

Tend to it, and in time, you’ll be that much more likely to tower over the competition.

Dominick Sorrentino is a senior writer in Chicago. He's a wordsmith who endeavors to use language, story-telling and creativity to solve problems. He enjoys pizza, the musical styling of A Tribe Called Quest, traveling, a good conversation and, of course, putting pen to paper.