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Serpstat updates 34 min read December 19, 2021

How To Stop Paying For Trash In The Backlink Index?

Research on backlink index data from Serpstat, Ahrefs, MOZ, Semrush, and Majestic.
Исследование данных ссылочных индексов Serpstat, Ahrefs, MOZ, Semrush и Majestic
Research on the backlink index
Зоряна Матюшенко
Customer Support & Education Specialist at Serpstat
Can you be sure that your SEO tool depicts the backlink diversity with 100% objectivity? While developing our own backlink index, we analyzed users' reviews to determine a more effective way to use an SEO platform to get the most accurate data.

And the results truly amazed us! (We honestly tried to avoid clickbait here, but there's no way around it). Long story short, the backlink index volume is not the crucial point.

The bigger the database — the lower the quality. Large databases often suffer from outdated data and duplicates. But wait, there's more! We've gathered a set of backlink insights you just can't afford to miss!
Building your own Backlink index is a resource-intensive process; that's why most SEO services use backlinks data they bought from vendors with crawlers. Such data is difficult to replenish and update because all changes are on the supplier's side. To influence the quality of the link data directly, Serpstat has developed its own backlink index.
The Serpstat Backlink index now includes 1.5 trillion links from 493 million domains. Crawlers add 2 billion unique links from 2.5 million domains daily.
As usual, SEO platforms often use the terms "the largest index," the most comprehensive database," "the best Backlink index" to describe their tools' abilities. But does quantity correspond to quality? We decided to go beyond the quantitative parameters of the Semrush, Ahrefs, MOZ, Majestic services to figure out the value they deliver in the analysis of the site's backlink profile.
Would you like to check your links within the Serpstat backlink index?
Click the button below, sign up, get a free 7-day trial and test all Serpstat tools!

How Are Link Indexes Different On Each Platform?

When comparing Backlink indexes, it is essential to mind different approaches to building links databases. For example, they can be formed from several "subindexes" containing data of varying relevance. Let's take a closer look at the differences in the architecture of the backlink databases of the abovementioned platforms.

Ahrefs' backlink index is built with the following subindexes:

  • Live — links that were found during the last crawl session and remain active until the subsequent crawling;

  • Recent — the subindex contains data on active, as well as lost links that were listed as "live" for the last 3-4 months. This list may include the links that were marked lost due to technical reasons.

  • Historical — all the links of the domain that have been assigned the "live" status, starting from 2016 (since the launch of the Ahrefs index). At the moment, these links might have lost relevance.
Semrush uses "fresh index". It consists of links recorded during the last six months of crawling.

MOZ displays "fresh" data from the last crawl. Although the data is not regularly updated for all links, higher-quality pages are the first priority. A machine-learning algorithm determines the quality.

Majestic's Index consists of the following parts:

  • "Fresh index" is all links considered active during the last crawl. The update rate is from 90 to 120 days.

  • "Historical index" - in addition to fresh-index data, contains all links that have ever been detected within the analyzed domain.
Serpstat backlink index only holds fresh links — those that were active within the last 70 days. This architecture allows updating the entire database for this period. However, if an active link is not found during the next check, information about it is stored for another six months in the "Lost Links" section. Therefore, users only get an up-to-date breakdown (whether it's a competitor's backlink profile or their own website).

Backlink index architecture
Backlink index atchitecture
Desktop PC software can be classified into a separate category of link analysis utilities installed directly on a computer or laptop. Examples of offline SEO services include Netpeak Spider and Screaming Frog for auditing and Netpeak Checker for key SEO parameters. This software needs to be downloaded and installed on a PC.

Among the main disadvantages of such programs is their slow operation compared to cloud services. In addition, there is a lack of 'cross-platform compatibility' and the need for initial software installation and updates for additional features. Speaking of advantages, such programs allow more convenient work with filters and sorting; all data is gradually downloaded from the database, and you can work with it locally.

Backlink Index Comparison: Methodology

Backlink indexes can be compared using different parameters. From the database size and the extent to which the data is complete — to the servers' and crawlers' capacity. In this study, we have included several parameters for quantitative and qualitative inspection:

  • Backlink index volume;

  • Data refresh rate;

  • Link accuracy;

  • Match rate (The uniqueness of backlinks).


Which parameters do you pay attention to when analyzing the backlink index?

The most important parameters regarding backlink indexes are freshness and relevance. When analyzing backlinks it's important to see links that are live right now and, therefore may be taken into consideration by search engines. I do not depend on links that have been live somewhen in 2007 or alike.

Secondly, I need to see the links that are relevant to the page. Seeing thousands of auto-generated "top 500 web pages"-links from all those well-known directory pages does not help if I miss recently published links in topic-related forums or user reviews.
    Sebastian Adler, SEO-Manager, Seoseb
    The main parameters:
    1. Link placement. You have to make sure it's not located in a directory with purchased links only (better to check manually);
    2. DR (using Ahrefs API);
    3. The quantity of referring domains and pages (using Serpstat API);
    4. The total amount of outbound domains and pages (using Serpstat API);
    5. The number of keywords for which the site is ranked. (using Serpstat API);
    6. Dynamic in the number of keywords in the last six months. (using Serpstat API);
    7. Thematic (better to check manually).
    Vladislav Naumov, Head of SEO at Inweb
    When analyzing a backlink profile of a website, I check the Domain Rating or equivalent of the referring domains, whether it's a DoFollow/NoFollow/UGC link, what Anchor Text has been used for the link, and when the link was last seen.

    Knowing how many links to my domain a referring domain is providing is also useful so I can see at an instant whether the link is being spammed or perhaps located sitewide. I think it's also beneficial to show the overall number of referring domains and backlinks my chosen domain has as a quick overview that can be monitored easily for any sudden spikes or drops.

    Though not essential, the average monthly traffic of a referring domain is a useful indicator to see how popular a website is without having to research it further using other toolsets, as would the statistics about the referring domain's own backlink profile.
      Steph Andrusjak, SEO Specialist,
      When running link building campaigns, I pay attention to a various set of criteria, whether they are qualitative or quantitative. My focus on the different parameters also depends on whether I'm running a campaign "at scale" or a more targeted approach.

      When working on an "at scale" campaign, i.e. looking at domains "in bulk", I'm looking first for DR, to some extent the UR, DomPop, TF and CF.
      When I go for the more targeted approach, I'm adding to this more granular criteria (rather qualitative), such as the trend of the visibility index of domains, language, follow/nofollow, or directly looking at the website: freshness of content, where the backlink could go, and other factors.

      If I'm looking at backlink index for monitoring and reporting, I tend to keep things simple: DR, DomPop, TF and CF. The more data point we bring, the more complex it gets, and the more difficult it is to report it to non-SEO.
        Baptiste Hausmann, SEO Manager at,

        I usually focus on the following parameters:

        • The traffic on the source page;
        • How many keywords from regional TOP-100 are listed on a page;
        • The type of link (not just Dofollow / Nofollow - Sponsored, UGC, link in comments, footer (site-wide link)). If you think about it, you can come up with many more types — link-picture, anchor, non-anchor, etc;
        • Page type (based on micro-markup or domain). For instance: Governmental, Educational, Catalog, Forum, Review, Blog;
        • Number of other outbound links on this page;
        • Date the page was published and the date of the first discovery;
        • Domain's topic;
        • Links' title;
        • Domain's title (useful for filtering out unnecessary domains);
        • Length of content on a given page;
        • Is this domain on the database of link exchange services? It would be handy to catch such;

        We find the data manually if we cannot catch it using a tool. Which, of course, is annoying — after all, we have to gather data from different spreadsheets and analyze it in a pivot.
        Nikolay Shmichkov, SEO specialist at SEOquick
        When analyzing a link profile, we pay attention to the following parameters:

        - DR and UR;
        - number of referring domains, backlinks, acceptors;
        - follow / nofollow proportion;
        - percentage of anchor / non-anchor links, as well as brand anchors;
        - availability (.gov, .edu domains);
        - the volume of traffic and keywords, etc.
        Igor Shulezhko, rankUP
        In off-page SEO, backlinks are a more crucial SERP factor. Before vetting the link for our client, we check whether it was penalized by Google in past, whether traffic comes from the country's we're targeting.

        We also check sites' top-performing keywords to confirm the site has pay-worthy keywords relevant to our client niche. DR metrics must be stable and have fewer outbound links, compared to inbound links volume.
        Raveel Nadeem, Co-Founder at Backlinks Guru
        The most important conditions for a backlink to be effective is a properly selected donor and a proper text environment of the link. When choosing the donor we usually pay attention to the Domain Rate, the frequency of publication of new materials, the presence of an SSL certificate, the relevancy by topic, regionality, the domain history, the traffic and DR dynamics. The text of the article itself is of great importance - it must be unique, with a proper keyword density. Choosing the type of the link - text or image and, respectively, anchor or alt text, is also very important.
        Nikolay Galinov, Head of SEO at Netpeak Bulgaria,

        Large Database: Advantage Or Disadvantage?

        To evaluate a link analytics service, it is customary to operate with the backlink index volume — the number of referring domains or pages to a site in the database of a specific platform. Such an indicator may seem convenient and understandable, especially if you must choose one tool from several alternatives. Here are the platforms' statistics from official sources.
        The volume of backlink index, architecture
        Volume of backlink index
        *Majestic does not use the "referring domains quantity" metric to estimate the index volume, so we do not analyze the statistics for this tool to compare different services correctly.
        However, an extensive database does not always indicate good quality data. Often, the index contains duplicates and outdated backlinks. You might notice spammy links in reports, which most likely appeared in the index once and continue to persist. Due to the index's architecture, there may be overlays of data collected at different times (historical, recent, fresh, and any other subindexes).
        Why is the link data so different?

        There are a few reasons:
        Frequency and rate of index update. The time it takes for the entire index to be updated, i.e., the crawler goes through and updates all links in the database. In Serpstat's backlink analysis reports, the last indexation date is displayed on the right side of the screen.

        External links indexation
        Links indexation date rate
        The platforms' speed and ability to find new data on the website, as well as delete irrelevant backlinks.
        Crawling pages specificities:

        • whether robots.txt, meta robots and x-robots-tags, noindex/nofollow tags are taken into account;
        • the availability of website during several simultaneous crawling sessions,
        • individual blocking of platforms through the above methods or by HTTP headers, by type crawler calls to the page (GET, POST, HEAD), by an identifier (User-Agent) or on IP level.
        What to do if the SEO tool does not detect your link?
        Take advantage of the Recrawling URL Tool. Submit a list of pages with new backlinks, and Serpstatbot will collect data within 72 hours.
        Considering the difference in the architecture and crawlers' algorithms of the indifferent platforms (crawling depth, taking into account the uniqueness of the host, IP, subnets), it is incorrect to evaluate the indexes totally by the number of backlinks or referring domains.
        An extensive database is purely a marketing goal. If the quantity of backlinks is higher than the competitor's, it does not mean that the data is better. Serpstat can make the index database larger in a month than all competitors combined, but our users will not benefit from this.
        Mikhail Broun, Serpstat
        It's not a secret that there might be low-quality outdated content hidden in a huge database. Therefore, data correctness and relevance essential, rather than just volume.


        Does the only size of the backlink index play a role? Is the relevance and uniqueness of the data still significant?

        The size of the backlink index and the relevance are important, but for me, the presence of a donor in the index is more important than just knowing that some garbage resource refers to my site. Ahrefs shows more links than Serpstat, but this difference is primarily due to junk donors that Google doesn't even index. We use the Serpstat API to get donors' data.

        It would be a perfect feature to filter only referring pages in the Google index.
        Vladislav Naumov, Head of SEO, Inweb

        No database gives 100% effect, and therefore the relevance of the data and the size are significant. So, some platforms can boast about many links and domains, but these domains might be duplicates.

        Inside the backlink index tool, you need a feature for searching for these duplicate links, filtering out junk links from site analysis reports, and other things (in Serpstat, this is implemented automatically). Otherwise, you have to analyze massive data tables, where you have to find valuable donors. Often, you end up with 100,000 lines, and there are less than three hundred actual exciting links.
        Nikolay Shmichkov, SEO specialist, SEOquick
        The quality of the data is the most important. For me, looking at the size of the backlink index is secondary. The most critical aspect of any tool, for that matter, is that the data can be trusted and is sufficient to define strategies and tactics to help my clients grow their business and organic reach. But of course, if an index is limited, then the quality of that data will be impacted.
        Baptiste Hausmann, SEO Manager at,
        For many scenarios, the size is important, as I want to get an overview of all the links pointing to a particular page. An indication if the link is live (and since when) is super helpful, but I tend to check the availability of the backlinks on my own in most cases.

        What can be super frustrating are duplicated links, as they create "noise". I like tools that try to list the "original" link and flag copies automatically.
        Stephan Czysch, SEO Specialist,
        Would you like to check your links within the Serpstat backlink index?
        Click the button below, sign up, get a free 7-day trial and test all Serpstat tools!

        Data Refresh Rate

        To determine how often data is being refreshed, we have to consider the whole data refresh cycle. It officially takes 60 to 180 days for the analyzed platforms to update the link information.
        Data refresh rate indicaror
        Data refresh rate
        But is this a realistic timeline? Let's analyze the data, provided by SEO platforms:
        We've detected outdated entries in the reports, which couldn't be there if the declared update frequency was true.


        What is the optimal refresh rate for the index? Is it important to get new links right away?

        I think this depends on the use case. For SEO analysis or audits a monthly updated but accurate index does its job. When it comes to penalty reconsiderations a or other urgent use cases it maybe helpful to have a very recent snapshot.
        Sebastian Adler, SEO-Manager, Seoseb,
        For some use cases (like copying your competitors backlink strategy or combating a negative backlink attack), high update frequency is crucial.
        Malte Landwehr, Head of SEO at Idealo,
        If you get a lot of backlinks organically, a link database updated in more or less "real-time" is nice to keep track of. This is also a great monitoring feature to keep track of your competitors' link-building efforts in real-time and set short-term actions.

        Nevertheless, I know that this is only possible to a limited extent, even with the greatest usage of link crawling resources. So a delay of a few days or weeks won't be that bad.

        Some SEO tool providers offer features to import link data from Google Search Console, Bing Webmaster Tools. Webmaster etc. That's particularly useful to get even more backlink data during link-building campaigns.

        Besides a "real-time" backlink index it's also useful to have a separate index that shows outdated, lost, or broken backlinks.
        Alexander Außermayr, SEO, CRO & Web Analytics,
        It is enough to update the database once every two weeks. I don't notice any practical value in catching a new inbound link the next day.
        Vladislav Naumov, Head of SEO at Inweb
        I can't claim to know the exact optimal frequency but for me, having the index refreshed once a month or on a quarterly basis is essential.
        Getting new links right away is of course an ultimate goal but not really realistic or practicable.
        Charlotte Maghe, Head of SEO,
        Every SEO specialist always wants to receive links immediately.

        Integration with a webmaster is super important - so that he quickly found backlinks in the index forcibly according to potential domains. So far, for today, this functionality is not detected, and we have to seek almost all requests in the search.

        There is a direct correlation between the links and positions, but the devil is in the details. A clean reference profile in white SEO is more critical than many quantitative metrics - I discovered this in 2016-2017 and after that. We often make backlinks within the outreach method, and we do not always get reports that links were placed by mail. Therefore, it is necessary to search for them manually because the backlink index of the platforms comes with the delay.
        Nikolay Schmitkov, SEO specialist at SEOquick

        Links Accuracy

        No tool can guarantee a 100% link display. For example, services track only 50-70% of the total backlinks a domain has, but it is frequently enough to work with a backlink profile regularly.
        Seeing all the links is not particularly necessary to analyze the backlink profile. Ahrefs, for example, shows a bunch of links, but there are also a lot of "spammy" websites which refer to low-quality content in a row.
        Vladislav Naumov, Head of SEO at Inweb
        However, it is still essential to get as much information as possible for some tasks. For example, if we are talking about recovering from a penalty.

        Match Rate

        Besides the size of the database, the frequency of updates, and the data coverage, it is crucial to focus on its uniqueness in comparison, especially if there are several link analysis tools to choose from.

        The share of unique referring domains is a parameter showing the percentage of donors in similar reports from competitors' platforms didn't detect.

        For this analysis, we randomly selected ten domains in different niches: from gaming to YMYL, but we tried to diversify the selection in terms of geography, niches, and approximate traffic. List of domains we researched:

        • (USA) - online (USA) - gaming
        • (USA) - web hosting
        • (USA) - the automotive industry
        • (USA) - environmental protection, government organizations
        • (USA) - IT, programming
        • (USA) - video games and consoles
        • (Poland) - game design
        • (Ukraine) - equipment
        • (USA) - a government health organization.
        For each domain, we've gathered the following data:

        • Referring donor by Serpstat;
        • Referring donor by competitive service;
        • Common donors to Serpstat and a competitor;
        • Unique donor domains Serpstat.
        Serpstat and Ahrefs, unique domains
        Serpstat vs. Ahrefs
        Serpstat and Semrush unique domai
        Serpstat vs Semrush
        Unique domains Serpstat and MOZ
        Serpstat vs MOZ
        Serpstat index contains about 60% of referring domains included in the index of alternative resources and about 40% of unique data not found in similar platforms.
        By examining a site's link profile using Serpstat, you will get more relevant data for analysis. And, using a combination of several services, you will see the complete picture of your current backlinks promotion.


        Have you compared the number of links in different tools for your projects? If so, what conclusions have you made?

        At Sortlist, we often check the number of our links in various tools such as Ahrefs or Semrush, it's always better to have multiple sources of data checkpoints.

        But as already mentioned, quantity is not the only criterion to take into account. This data should always be taken with a grain of salt. Spoiler alert: the data still shows a lot of spammy links coming up.

        As main points, I would say that you should always weigh your data and those of others, and try to look at quality rather than quantity, and also relevancy is key! So yes, checking your backlink profile in different tools is always a good idea.
        Charlotte Maghe, Head of SEO,
        I have used a lot of different backlink tools and databases. Most of the time it seemed that having a large index is the most important problem they try to solve.

        Accuracy and the possibility to tweak the way those tools gather their link information are things I always have to struggle with. I do not look at index sizes but try to use databases that represent a data set that gives me the most accurate data.
        Sebastian Adler, SEO-Manager at Seoseb,
        The number of links displayed in different SEO tools can differ wildly. What I have noticed is that Serpstat seems to cut out the organic spam that websites naturally pick up and just shows the links that matter.

        I think Serpstat is the first I've seen to do that out of the different tools I've used over the years. Whilst this is helpful to cut out the noise, knowing about the spam sites is sometimes useful in case those domains are actually impacting your domain's health.
        Steph Andrusjak, SEO Specialist,
        I think it is important to never trust one single tool, but to combine the data from all of them (plus the Google Search Console), to get a wider overview. The one insight I believe is often overlooked is discounting disavowed links and looking for the hidden ones to put them into consideration.
        Timo Fach, Head of SEO at
        Yes, I have done it many times.

        So far, no tool gives clear parameters needed for filtering out, so you have to sort the domains and check them separately.
        For example, I need to check in Google not only NOFOLLOW, but also SPONSORED / UGC content. If you need a domain comparison tool — Serpstat has a more suitable implementation.

        Serpstat has a good link analysis tool, and its data is worth exploring.
        Nevertheless, it would be helpful if there were more integrations with the webmaster to find your links promptly and, of course, have excellent methods for sorting link data. I spoke about it also according to the database size, from their history to the current condition (Serpstat already has these features). And for sorting, I lack several metrics that no one has yet, and I have to check links manually.

        Nikolay Shmichkov, SEO specialist at SEOquick
        Yes, I use different tools. The core insight here from me is that you never know the source of data that is being presented. Most of the time, every tool shows different results, making it harder to decide on which data to rely on. My strategy is to compare, check, and sort the data manually so I can get a most complete overview.
        Gundel Woite, Manager at Jenpix
        In everyday work, I use several tools to obtain more detailed data. For now, no single tool can guarantee a 100% link display. Ahrefs shows a lot of links, but many of them are junk. Some data from Search Console is also useful.

        Serpstat's solution is pretty good so far in terms of convenience (it has an API function for analyzing backlinks and a URL rescan tool). When you work with massive data, it saves a lot of time.

        Aleksey Biba, Head of SEO,
        Would you like to check your links within the Serpstat backlink index?
        Click the button below, sign up, get a free 7-day trial and test all Serpstat tools!

        Why Serpstat?

        So how do you stop paying for garbage in service link indices? Above, we've discovered that having a lot of reference data doesn't matter if it's outdated or incomplete.

        Since the link ranking factor is one of the leading in SEO, it is necessary to pay careful attention to the analysis of links and the quality of the analyzed data.
        Serpstat Backlink Analysis will help you obtain the necessary information to research (even if you are already using another tool).

        Serpstat focuses on the quality of the index data. And, in addition to the regular reports of link analysis, such as:

        • Referring domains
        • Backlinks
          External links
        • External domains
        • Link anchors
        • Top pages (by link diversity)
        The platform has many unique link-building features - Links intersect, Redirecting Domains, Malicious Domains, and URL recrawling tool.

        Serpstat Recrawling URL Tool will provide data on links "on-demand". Send a list of pages (up to 500 URLs per day) with new backlinks, and our robot will collect data on them within 2-3 days. The feature is available to users with any paid plan.

        The tool will be helpful if you purchased links and want to immediately track their impact on SDR to remove them if necessary and avoid negative consequences. Also, if your client requires up-to-date information "for today" and new links have not yet been displayed in the report.
        Recrawling tool
        Links intersect, is a tool that allows you to carry out simultaneously the comparison of the link diversity of several domains to find common and unique donors for each analyzed web resource.

        For example, you want to find high-quality and relevant link placement websites. Previously, you would have to explore each competitor separately and manually search for common sites in the reports. Now it is enough to find several relevant competitors, enter their domains in the tool and automatically find those donors who link to all of them.
        Links intersect
        Redirecting Domains - a report that shows sites that link entirely to the analyzed domain while transmitting link weight. Building up entire domains that are redirected to a website is a popular link-building strategy. Track the influence of this method on the domain and find out which of the competitors buys drops and attaches them to the website.
        Referring redirecting domains
        Malicious domains. If your site received a link from a questionable resource, you could see the platform and type of vulnerability targeted by the "infected" donor.
        In the API for backlink analysis, there are 16 methods for data around referring domains and pages, malicious donors and acceptors, dynamics of your link diversity, anchors, leading pages by the number of backlinks, donors intersect, etc. Automate routine SEO processes and create custom reports.
        Do you have technical questions about the link analysis service? Contact Serpstat support team. Our specialists will answer within ONE minute to guide you. Only a few platforms provide free support. And we are among them! No limits and restrictions, even for users without a paid subscription.
        Would you like to check your links within the Serpstat backlink index?
        Click the button below, sign up, get a free 7-day trial and test all Serpstat tools!


        Most of the time, the size of the backlink database (the number of referring domains or pages) is used to evaluate indexes, and this indicator seems to be straightforward. However, only the relevance and completeness of the data are decisive factors.

        SEO specialists often take advantage of different platforms and combine data from several reports and indexes for a comprehensive analysis. One of these tools in your arsenal can be Serpstat, which, in addition to its backlink index, also has numerous unique reports for backlink analysis.

        Well, we have shared various insights from the world of backlinks. Leave comments to discuss the article and ask additional questions about backlink diversity analysis in Serpstat :)

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