How Ahrefs Counts Links and Domains

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Every backlink application will save unique links.

When constructing an index of the net, businesses need to make many decisions around running, parsing, and communicating info. While there is likely to be a whole lot of overlap between indicators, there is going to be some differences based on each organization’s decisions.

In the title of transparency, we would like to let folks understand more about Ahrefs’ link indicator.

Links take users from 1 page to another once clicked. There are many techniques to create themwith the most frequent way being the classic HTML element with an href attribute.

However, it is possible to create connections with different components, such as:

  • Onclick
  • Button
  • Ng-click
  • Option/value
  • And longer…

In an perfect world, whatever acts as a connection could be saved. Unfortunately, we do not reside in an perfect world. Neither Ahrefs nor Google shops all kinds of links since it is not an efficient procedure to load every page and click on every connection. That’s what you would need to do if you would like to obtain each the links that work for consumers. 

Instead, crawlers normally fetch webpages, potentially render themthen extract and save various kinds of links. All crawlers operate otherwise, so let us discuss how we can do things here in Ahrefs.

Links we shop

Here are the kinds of links we shop in our indicator.

External hyperlinks

Links from 1 site to another created utilizing the classic HTML element with an href attribute.

Internal hyperlinks

Links from 1 page onto a site to a different page on precisely the exact same site. There are 22.21 trillion inner backlinks in our indicator. That’s much more extensive than our reside outside connection count. We’re the sole SEO instrument where you are able to get this information without a custom made website crawl. We use the internal connection info in the URL Rating (UR) calculation, like the way Google would utilize it inside their PageRank calculation.

If you need to determine if we first and last crawled a URL, it is possible to assess the “Best by links” report in Site Explorer. There are tabs for the two External and Internal Links.

best by links report

Links we can shop

Here are the connections we shop under certain conditions.

Links added with JavaScript

Because Google leaves all pagesthey could count links which are added with JavaScript but are not at the HTML code. Rendering at scale requires far more resources than simply downloading the HTML of webpages. At Ahrefswe leave around 80 million pages every day. That’s the reason we’ll have a few of those links added by JavaScript, but maybe not all them. We’re now the sole SEO tool which leaves during our regular functioning of the net, thus we have some connection data which other tools do not have.

Howeverwe just rely hyperlinks inserted with JavaScript whenever they’re in the arrangement of an HTML element with an href attribute. You’ll view these links labeled in the backlinks report as “JS,” such as this:

js link

Links from webpages with URL parameters

Parameters are improvements to some URL such as: Tag =something. You might observe a number of those URLs within our index, but they are usually parameters which reveal different content. In most scenarios, pages with parameters may demonstrate exactly the exact same content. We have many programs in place to combine URLs to canonical models and extra protection for boundless crawl paths. Other tools might not make the very same conclusions or have the very same protections in place. As an outcome, they can count basically the exact same connection many times. 

Links we strive to not shop

Here will be the hyperlinks we all do our best to not shop.

Links from webpages with URL parameters

As mentioned previously, you can find good and bad kinds of parameters. We do your best to not keep those which are replicated.

Links from webpages in boundless crawl avenues

These paths produce an endless number of possible URLs. Parameters are just one way they can form but are filters, dynamic content, and broken relative paths such as hyperlinks. As mentioned previously, we’ve got lots of protections in place for hyperlinks on these kinds of pages so they’re not as inclined to appear within our reports. Respecting canonicalization and how we prioritize crawling pages are only two of these protections. Every indicator might need to manage these infinite distances, but there is possibility for those pages to populate link points. 

Links we do not shop

Here are the links we never shop.

Links from PDFs or other files

Google converts many document formats to HTML and indicators as they would any other webpage. This implies they rely links in these records. I don’t feel any SEO tool now indexes these hyperlinks, but we probably need to. I believe one day we shall, but I am also worried that the hard work and resources necessary for this will not be well worth it. According into Google Webmaster Trends Analyst John Mueller, links in PDFs don’t have any practical effect in web search.

Links from iframes

Iframes let a different webpage to display inside a webpage. Because of the, Ahrefs does not count hyperlinks in iframes. Howeverthey are revealed to consumers, so other programs can count them though the content belongs to another page. Google may or may not rely on these hyperlinks.

Links from pages not indexed

We shed these links.  There are mixed messages from Google agents on if they utilize these in connection calculations or not. Different tools can make unique decisions.

Same hyperlinks from multiple IPs

One fun fact about the net is that websites may function the same webpage from multiple IP addresses. If that is the situation, a hyperlink indicator may count the exact same link multiple times. We do not do so. We link hyperlinks with the pages they’re on. 

Multiple links to the exact same page from one page

Currently, we just record 1 variant of a connection on a webpage. If you connect to a page at the menu and then again from the body material, we’ll only count one of those links. We may alter this in the long run to provide users more information, but that is the present condition. Google will rely all variants of hyperlinks for departure PageRank but may only use 1 variant’s anchor text.

Other link associated items which affect the indicator

Understanding the way we count hyperlinks is 1 thing, but many different things can influence what does and does not get counted.

Number of hyperlinks each page

I do not think we have a limitation for the amount of links we count per page, however we have a page size limitation that may eventually affect the amount of links we view. Google urges no more than a few thousand links per page.

Redirected or canonicalized

At Ahrefswe hope each of redirects and canonical tags and combine connections where sites tell us . For Google, this can be much more complex as they have lots of canonicalization signs that decide which page is your cause a canonical cluster. We keep matters easy as it is not possible to understand exactly how Google perspectives every circumstance, and it could confuse our customers when we handled canonicals and reconnect otherwise each time.

These connections have been labeled in our accounts with “301”, “302”, or “Canonical,” for example:

Which domain get found?

In Ahrefs, we’ve got the Referring domain names  report which reveals all of the domain names linking to a site or page.

But how do we count domain names?

You would believe this could be a simple question to answer. It’s only, correct? Unfortunately, matters are a bit more complicated as there are several methods to count domain names. One alternative would be to deal with every registered domain for a domainname — that appears to be the way Google aggregates them Google Search Console. Another would be to take care of each subdomain as a distinct domainname. You may also aggregate some parts of a website rather than others (what Google does), proceed by each section on another technician pile, etc. ) There are several choices.

At Ahrefs, we’ve got ~175 million domain names post-vetting. The vetting procedure involves removing spam domain names and breaking some subdomains where we have decided that distinct users control different places. We utilize a personalized record for this, however there is a somewhat similar people record in

ahrefs domains

It is essential to be aware that distinct domain definitions could lead to massive variations of speaking domains. Here are a few examples of items that others, perhaps not Ahrefs, can count as different domain names:

  • Mobile variations subdomains (,, etc.)
  • Country/Language subdomains (,,,, etc). There could be exceptions to this in our own indicator, for example, but this isn’t standard practice.
  • Random subdomains (,, etc.)

Another conclusion backlink tool suppliers need to make is if they ought to count some subfolders as distinct domain names. For example I believe most connection indicators would rely unique websites on famous platforms (e.g.,, as distinct domain names because different users command them. But why not the exact same for websites like or even At Ahrefswe do not currently do so, but there is a chance we can in the long run where we understand various men and women control every subfolder on a website.

The point here is that there are lots of methods to count domain names. That’s evident once you examine the varying amounts from businesses that count websites online. According to Verisign, you will find 370.7 million registered domain names in Q3 2020 across all TLDs. According to Netcraft, you will find 1,229,948,224 websites across 263,787,870 unique domain names with 193.8 million active websites in November 2020. According to Internet Live Stats, there are approximately 1.8 billion sites with less than 200 million now active. Each firm obviously has a distinct methodology for counting domain names.

To recap, what we do in Ahrefs is take each of the websites we all know about and eliminate many static and spam domain names, then put in some for subdomains on websites like That’s the way we return to our overall domain count of ~175 million. Other indicators may do so differently and think of unique counts.

Why we can not observe all hyperlinks

As we find webpages by crawling the internet, we could only do this on websites we are permitted to crawl. If website owners obstruct AhrefsBot in their robots.txt document, we can not crawl their website. For instance, if you buy a backlink from and cubes AhrefsBot, then we can not crawl their website and your backlink will not appear in Ahrefs. IP cubes, user-agent blocks out of servers (distinct from robots.txt), server timeouts, bot security, and several other items may also impact our ability to creep a few sites. Crawling the net at scale is not simple.

We have multiple connection indicators

Each tool must make decisions about information storage and recovery. At Ahrefswe divide our data into several indicators.

  • Live — the hyperlinks we find that are still busy on the internet. This best reflects the current state of the internet and is exactly what most of our customers will find most helpful.
  • Recent — hyperlinks we’ve observed active on the internet at the previous 3–4 weeks.
  • Historical — each of the links we’ve ever seen. This will be the most extensive listing, but with lots of connections that no longer exist.

You can change between indicators within our backlink and discussing domain name reports.

ahrefs indexes

Other indicators might decide to show all of the information they’ve ever seen, and while this implies they may demonstrate a great deal of links, a lot of these links might not exist .

Final ideas

We needed you, our customers, to get more info on the indicator so you are able to make informed decisions. We also would like you to let us know whether you believe we ought to change things and .

If you are currently comparing link indicators or have questions regarding our information, don’t hesitate to reach us out with any queries or for clarifications.

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