Ahrefs’ SEO metrics explained: What they mean and why they’re so good

Tim Soulo
Tim is the guy responsible for marketing and product development at Ahrefs. But most importantly he’s the chief evangelist of the company.

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Data: Ahrefs' Content Explorer
    Most people think of Ahrefs as a powerful “backlink checker” tool. But in reality, “checking backlinks” is just one of the many things that you can do with our huge data index.

    If you look at the big picture, Ahrefs is a data company.

    We collect data, we process data, we store data and, finally, we build all sorts of tools that let you use our data in your marketing.

    So yeah, we LOVE data! The “big” one:

    Big data is a term for data sets that are so large or complex that traditional data processing applications are inadequate. Challenges include analysis, capture, data curation, search, sharing, storage, transfer, visualization, querying, updating and information privacy.

    But before I explain what the different SEO metrics in Ahrefs mean (and how we calculate them), I'd like to brag for a bit about the monstrous infrastructure that's running behind the scenes.

    Ahrefs Data Index

    Here are a few core numbers, representing the size of Ahrefs’ index (you can always find them on our homepage by the way):

    In our index:

    • 12 trillion known links
    • 3 trillion known URLs
    • 200 million root domains

    Powered by:

    • 20 petabytes of storage
    • 200 terabytes of RAM
    • 15,000 CPU cores

    Every 24 hours, our crawler visits over 6 billion web pages and updates our index every 15-30 minutes.

    Creating a robot that will crawl the web and store web pages on your hard drive might sound like an easy thing to do.

    But that’s until you try to achieve the crawl speed of 200 million pages per hour. Or try to store all this data in such a way that your customers can make a call to the database and have all their graphs and reports built in seconds.

    That’s why the majority of our backend infrastructure was built in-house. All existing solutions simply couldn’t keep up with the volume of data we operate or, if they could, were too expensive. As of today, we’re running a custom big data database with ~85 trillion rows.

    In fact, according to a recent third-party study of the "most active good bots," Ahrefs boasts the second best crawler after Google, outperforming Bing, Yahoo, Yandex, Baidu, and pretty much everyone else:

    And that research was carried out before we drastically improved our crawl speed:

    So, as you can tell, we’re seriously obsessed with big data, and we absolutely love all the challenges associated with it.

    It looks like our CEO isn't going to settle anytime soon, either:

    Ok, enough bragging about our (and yours too, actually) data.

    Let me explain the SEO metrics that we have in Ahrefs.

    #

    "URL Rating" measures the strength of a target URL's backlink profile and the likelihood that the URL will rank high in Google.

    UR is measured on a logarithmic scale from 1 to 100, with the latter being the strongest.

    Sidenote.
    “Logarithmic” means that it's much easier to grow your page from UR 20 to UR 30 than from UR 70 to UR 80.

    We often see people explain Ahrefs’ URL Rating as a replacement for Google's PageRank metric, but that's not entirely accurate. UR and PageRank aren't the same things.

    We indeed started out with a PageRank-like formula, but then “UR” underwent quite a few iterations with a goal of creating a metric that would have the highest possible correlation with Google rankings.

    And, as you can tell from the graph below, the URL Rating correlates with Google rankings better than any of our “unprocessed” backlink metrics:

    backlink-factors-on-page

    Moz has a similar metric to our URL Rating called Page Authority, which predicts the likelihood of a page ranking high in Google. And, according to their own research study, it correlates with Google ranking slightly worse than our metric.

    #

    "Domain Rating" shows the strength of a given website's overall backlink profile.

    DR is measured on a logarithmic scale from 1 to 100, with the latter being the strongest.

    Domain Rating correlates with Google rankings pretty well, but not as well as the URL Rating—which suggests that you might be able to outrank high-authority sites if you build more backlinks to your page.

    DR is a great metric for picking websites to build links from. As a general rule, you need to aim to get backlinks from high-DR websites because they carry more "weight."

    Here are a few popular questions our customers ask about DR:

    Q1: “I didn’t lose any of my backlinks. Why did my DR drop?”

    A1: “That's because other sites have gained a lot of backlinks. Think of it this way: when a DR-100 website gets more backlinks, we can’t make it DR-101. So instead we push all the other websites down by 1. That's a very raw explanation of why you might see a drop in your DR while no backlinks were lost.”

    Q2: “My competitor doesn't have links from high-DR sites, so why is his DR higher than mine?”

    A2: “If a high-DR website links to thousands of other sites, we value their links less. But if a low-DR website only links to a few sites, we consider these links quite powerful. Your Domain Rating doesn't solely rely on the number of high-DR sites that link to you. It also takes into account how many other websites these high-DR sites link to.”

    Q3: “Are links from low-DR sites bad for me? Should I disavow them?”

    A3: “Low DR doesn't mean a website is bad. It just means they don't have a lot of links. If you need to identify bad links, check out this article: “An In-Depth Guide to Link Quality, Link Penalties and “Bad Links”

    #

    If you take all the websites in the world and order them by the size and quality of their backlink profile (basically by their DR), you’ll get the Ahrefs Rank.

    So Ahrefs Rank #1 belongs to the website with the best backlink profile, #2 is just a bit worse, #3 is a little worse than that, etc.

    You can see the full list of domains sorted by their Ahrefs Rank here.

    Here's one other way to understand it.

    Alexa Rank shows you how much traffic a website has relative to other websites in the world. And Ahrefs Rank shows you how good the website's backlink profile is relative to all other sites in the world.

    Here’s the most popular question about Ahrefs Rank:

    Q: “My backlink profile is growing, but my Ahrefs Rank is going down. Why?”

    A: “Because other websites are getting new backlinks faster than you. What happens here is very similar to my above answer about a drop in your DR.”

    #

    As you’re browsing backlink reports in Ahrefs’ Site Explorer tool, you might notice a “Live/Fresh” switch that changes the numbers in your reports when you toggle it.

    What is the difference between the two?

    Like I mentioned above, Ahrefs' backlink index is updated every 15-30 minutes with all the new backlinks our crawler has found.

    But not only do we crawl new pages, we also re-crawl the old ones. And, therefore, some of the links that were seen live might disappear by the time we re-crawl them.

    We remove all these “dead links” from our “Live” index right away, but they stay in the “Fresh” index for 3-4 months so you have enough time to act on this information.

    For example:

    The “Fresh” index shows that Brian Dean used to have a backlink from an article at Outbrain, but it got removed for some reason:

    Lost links are easy to spot in Ahrefs reports

    Lost links are easy to spot in Ahrefs reports

    Knowing that, Brian could reach out to Outrbrain and persuade them to put it back.

    A link saved is a link earned, right?

    #

    "Keyword Difficulty" shows how hard it would be to rank in the top10 Google search results for a given keyword.

    KD is measured on a logarithmic scale from 1 to 100, with the latter being the hardest.

    This SEO metric will save you a lot of time doing keyword research. But it should only be used for pre-vetting keywords, as nothing beats good old manual review of the SERPs.

    Please also note that our KD scale is non-linear. So KD 50 is not a "medium" keyword difficulty:

    In fact, I wrote a pretty detailed article on the concept of "keyword difficulty" in general and how our own metric fits there: "How To Gauge Keyword Difficulty And Find The Easiest Keywords To Rank For".

    And you can read about the rest of the SEO metrics in the Keywords Explorer tool here: "Keywords Explorer 2.0 by Ahrefs: Setting new standards for keyword research".

    Here are some of the most popular questions about Keyword Difficulty:

    Q1: “Do you take "on page" factors into account when calculating KD?”

    A1: “No. Ahrefs' Keyword Difficulty is based solely on the backlink factors of the top10 ranking pages.

    We don't look at the keyword usage in a Title/URL/H1 because our recent study of on-page SEO factors revealed it has only a minor impact on your ability to rank.

    Calculating the overall relevancy of a page might be a good addition to KD, but we haven't tackled it just yet.”

    Q2: “The #1 result is very strong! And your KD is way off!”

    A2: “Ahrefs' Keyword Difficulty score only shows you how hard it would be to rank in the top10, not #1. When you're in the top10, a lot of other ranking factors kick in, so it's almost impossible to accurately calculate your chances of ranking #1.”

    Q3: “How accurate is your KD score compared to other tools?”

    A3: “It's impossible to objectively compare KD scores from different tools because there's no "base KD value" to compare against. Each SEO professional uses his "gut feeling" as a base value, which obviously differs from person to person.

    And yet, the only KD study that was carried out to this date showed that Ahrefs has the most accurate KD score of all available solutions.”
    number-of-wins

    #

    Search volume was one of the hottest topics in SEO last year.

    All because Google decided to take it away from the free users of Google Keyword Planner tool.

    Ever since that happened, our customers keep asking us this question:

    "How accurate are the Search volume numbers in Ahrefs?"

    Google Keyword Planner is known to have quite a few "dirty secrets," which causes SEO professionals to question the accuracy of their data.

    So you'll be glad to know we no longer rely on GKP alone for calculating our Search volumes.

    We pair their numbers with the data from clickstream sources, allowing us to calculate more accurate search volume numbers.

    I've shared more details about it here.

    And I plan to write a dedicated article about the issue with Google's search volume and how we solve it. So if you don't want to miss it, please subscribe to the Ahrefs Blog.

    #

    For any website you put into Site Explorer, we'll show you the number of keywords it ranks for and the estimated amount of organic search traffic it gets:

    And if you switch to the "Organic search" tab of the "Overview" report, you'll see this beautiful graph:

    So how accurate are these numbers and how do we calculate them?

    Organic keywords

    The database of keywords in Site Explorer is approaching 200 millions for the United States alone.

    But, obviously, even a database that big can't cover all possible search queries that people might put into Google. That's why we tend to underestimate the total number of keywords a website is ranking for.

    Organic traffic

    This is our estimation of how much traffic a target website or URL gets from organic search. We calculate it based on the keywords we see that website or URL ranking for.

    And because we don't have all possible keywords (see above), we tend to drastically underestimate the search traffic of a given website.

    For example, for the Ahrefs Blog, we underestimate organic search traffic by 5x:

    But as soon as you try to compare two websites from the same niche, you get a very accurate picture.

    Ahrefs shows that our company blog gets around 10x more search traffic than my personal blog:

    Which is exactly the case, if you look at the numbers from Google Analytics:

    In other words, the organic traffic numbers you see in Ahrefs should not be treated as exact values but, rather, should be used for comparing websites with each other and seeing trends in your search traffic over time.

    Back To You

    So these are the metrics we get asked about the most.

    I hope that this article helps you better understand Ahrefs' reports and make them more actionable.

    If you have any other questions about the numbers you see in Ahrefs, feel free to ask them in the comments and I’ll be happy to help you.

    Tim Soulo
    Tim is the guy responsible for marketing and product development at Ahrefs. But most importantly he’s the chief evangelist of the company.

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    • Olivier

      How do you get the non-geo positions for each country?
      when i Google something, my results are city-bound.

      • we get this data from our data providers, so I’m not exactly sure how they do it.

        • Olivier

          Then how can i be sure this isn’t a location based resultset?
          Or maybe this could be a nice feature request; show rankings for specific city/geolocations

    • Ashwin Chotoo

      Can you please clarify one thing please. I do understand UR and DR, but from a very basic position, please answer this question. When i am looking for sites to target for links, Should i be looking at the UR or DR. Which is a more precise snapshot of the website.

      • you should try to get links from domains with high DR and pages with high UR 😉

        • Hey Tim,

          I would much rather use this than Majestic so when buying expired domains is a good rule of thumb is gettin domains with a DR 40+ or will 30+ do well for a PBN site?

    • Thank u Tim Soulo

    • Jamie Richards

      I’ve genuinely been waiting for this for a long time!

      • hey @jamierichards_seo:disqus , sorry it took me so long to reply, but I just updated this article.. thought you might want to skim through again 😉

    • Most important keyword metric is Keyword Difficulty (KD). KD is game changer for ranking keywords. Excellent work Mr. Tim Soulo

      • thanks a lot for the feedback, Zahid! 🙂

    • John Schnettgoecke

      Happy to see this article this morning. Thanks, Tim!

    • Victoria Lysenko

      Very nice article! Thank you!

    • Tim why does a domain have show different UR, for example my non www version and the www version both have different UR. Which one should I trust? Why is that?

      • UR stands for “URL Rank”… http://www.domain.com and domain.com are technically different URLs 🙂 Hope that makes sense

        • Thanks Tim I figured that was it. I have a REQUEST that everyone will appreciate and now that I am talking to boss I will ask. On the Standard Plan you should definitely change the position tracking to TOP 100 not TOP 50. To jump from the Standard Plan to the Advanced is a big price jump. Top 50 just does not cut it. Can you make it happen for all of your users? We would all appreciate that.

    • > Is this # of RD’s (dofollow AND nofollow)?
      yes.. that’s a total # of RDs

      > If it’s total what happens if the #1 has 1000 RD’s, and the rest 9 results have 10 RD’s in total, will the KD be 90?
      we remove outliers before calculating average 😉

      • I have a similar question to Ian’s.

        Does UR take nofollow referring domains in to consideration?
        If it does that will be very misguiding.

        Preferably UR should be based only on dofollow referring
        domains.

    • Top Content vs Top Pages. From what I can see content is by shares and top pages is by links. Are there any other differences?

      • we have come requirements to say that a “page” has “content”… so “Top Pages” report is based on all pages we know, while “Top Content” is based on pages with content only

        but I agree, that is confusing.. and we might merge these two reports soon

    • Tim, if a site has incoming links that point to pages that have been removed and not redirected (i.e. they return a 404 or 410), are those links ignored for purposes of DR?

      What if they are 301 redirected to another page? Is that treated exactly the same as a direct link to that destination page, is some link juice lost in the redirect, or is it ignored? (thinking about both DR and UR)

      • yeah.. links to 404 pages are not calculated in DR.. we tackle this situation same as Google — they don’t count links to 404 pages

        but if you 301 these links to a live page, we do calculate them.. again, just like Google does 🙂

    • Việt Hùng Ase

      I can’t see full list of domains sorted by their Ahrefs Rank, you can fix it.

    • According to Ahrefs data,URL Rating (UR) is the most ranking factory. Well, my question is that, when I got a editorial dofollow backlink from DR 80+, but when I analyzed that backlink from Ahrefs, it shows DR 80+, but show UR only 30+ or 40+, how you analyzed backlink UR rating. How can i improve my UR rating from DR 80+ editorial dofollow link. If I am getting an editorial dofollow backlink from DR 80+, then why not my UR is 70+ or 80+. How can i improve my UR rating for backlink from DR 80+? Well Please answer Mr @timsoulo:disqus

    • I have been always forget what the actual meaning of these short-forms while using ahreafs. Thank you for sharing.

    • I was using ahref for a while but saw this info now. many new things i did not know thank you 🙂

    • result togel

      Top Content vs Top Pages. From what I can see content is by shares and top pages is by links. Are there any other differences?

    • happy tu read your article, thanks for sharing, helpfull explanations

    • Its really a good article but how do i increase domain rating.

      • just build more links from diverse domains 🙂

        but actually.. you should not have DR as your main KPI.. I’m sure your end goal is traffic from search, or even sales. So DR is a secondary metric, that helps you see the strength of your backlink profile.

        Even a low-DR website can get nice traffic from search, if they pick the right keywords to target

      • Excellent

    • Great Tips for the seo. It is very useful for my website. Good sharing..

    • Its really a nice post and it is very useful for my website.

    • Very good analisys!

    • So, I’m a bit confused on just the Ahrefs rank portion. Using Ahrefs, we have been working diligently to procure backlinks for a client of ours, and have been extremely successful, getting .edu links, etc. Their UR rank has increased tremendously, DR rank has stayed the same, yet their Ahrefs rank has gone down pretty substantially. Their keywords have increased, along with site traffic, and we are in the process of fixing their site errors. Something isn’t adding up.
      Meanwhile, I’ve been using my website as a comparable, using the same methodology, and everything is steadily rising in all categories. It seems as if something is amiss.
      Great article. Thank you.

      • hey Brad. Ahrefs Rank is kind of “precise,” so as we reorder millions of websites in their rank — you see a lot of changes over time.

        But DR is scaled down to only 100 points, which are logarithmic. So the higher you get in DR, the harder it will be to get that extra point. While Ahrefs Rank can be growing in thousands per day.

        And finally, UR and DR are not connected directly. UR is a score of the page. In your case — the score of your homepage. The fact, that your homepage grows in UR might not be enough to get an extra point in DR.

        hope all of that makes sense 🙂

        • Absolutely makes sense. I’m tracking on every part but the Ahrefs rank. Is the Ahrefs rank based on links alone, dofollow, domain links, or a combination of all?
          I really appreciate your help on this, Tim. I’ve been racking my brain on this for a month. All of my agencies efforts have grown a specific clients metrics considerably, while watching their Ahrefs rank drop by nearly 400k in Ahrefs rank. Every other metric has grown considerably. 

    • Nirnay Patel

      Great article Tim! Definitely sharing it on Twitter!

    • Prateek Agarwal

      Is there a way from which I can see a list of all low KD keywords and high volume keywords in my domain i.e finance.

    • Just 2 days ago my team member asked me How Ahrefs calculates DR and UR. At that moment I have not proper answer but now I have.

      Thanks for the explanation. We loved to use Ahrefs tool.

    • Meanwhile, I’ve been using my website as a comparable, using the same methodology,

    • Clare Hoang

      short & sweet article!

    • Hello Tim,

      Thanks so much for the post..is there a database of HIGH DR websites? Also is DR the same as PR page rank?

      Paulina

    • Hi Tim,

      Great article. We are just getting to grips with Ahrefs and I have to say this is a sweet piece of kit. We have been using SEMRush, which is amazing, but the two combined is so important to our success for our clients.

      Rgs,
      Ibby

      • I second that, been on SEMRush for a few years, combined now with Ahrefs is a sweet treat.

    • Saj

      Whats the time period for the organic traffic estimate? The most recent month? Last 30 days? 4 years?

    • Jordan Manco

      Tim, I felt like this was a good read, and that it was well written.

    • my Ahrefs Rank is drop but my UR doesn’t , why ?
      is UR calculated by organic traffic ?

    • On the topic of “Fresh” vs. “Live” … When Ahrefs shows that I have a broken link and I then fix or remove it, how come it stays in both the Fresh and Live views of broken links for a long, long time (years)? If your bot refreshes every 15 minutes, how can a “Broken Last Check” be from 20 months ago (which I have several in my reports)? Thank you.

    • Good Article. Today I understand Ahrefs rank.

    • Excellent Brag (Explanation) 🙂 Just one question : Where do you host these servers?

    • Very detail and usefur article. Thank you very much, Tim !

    • My domain is top for many keyword but my Ahrefs Rank is drop and my DR doesnt, can anyone tell me why?

    • short & good article!

    • Thanks for sharing

    • good article.

    • ComUP

      Your data are way more unrealistic I just search for some competation organig traffic and you give some kewwords 1/10 of it’s real traffic volume ,
      I was having blog ranked n 1 on that keword I got 7k+ traffic daily while the report show me 300 traffic . ppl you should improve your data and give us real statics .