If you’ve been putting SEO to use, you know that Google’s algorithms are opaque, and measuring the value of your SEO efforts can be difficult for that reason. When it comes to links, what is the best way to determine how effective your link building strategy is? How should we decide between link opportunities? Which metrics are best, and which are most practical?
I aim to explore these questions and offer some practical advice in the following guide.
What Are The Best Metrics To Check For A Quality Backlink?
I am of the opinion that the best metrics to check for backlink quality are metrics that don’t rely too heavily on the search algorithms and instead are strong indications that these are the kinds of sites Google wants to rank. These aren’t always the most convenient metrics, but they are the most instructive and likely to provide meaningful long-term information.
I’m not arguing against metrics such as Domain Authority or Page Authority, and we will be discussing those in-depth as well. But, the best metrics are update-proof because they are deeply rooted in the brand’s actual strength, as a traffic vehicle.
Let’s address those now.
Branded Search Volume
In a correlative study conducted by Tom Capper, branded search volume has a stronger correlation with Google rankings than Moz Domain Authority, which is considered by many to be the gold standard for determining how valuable a link from a domain is.
Branded search volume is simply the number of people who search for a specific brand. Raw traffic data isn’t available, and you can’t aggregate search data from every platform, but getting the number of people who search for a brand in Google is the next best thing.
You can obtain this information by going to the Google Keyword Planner and simply typing the brand name into the tool:
Clicking “get started” will take you to a page that lists the total amount of traffic for the brand name and for associated keywords.
If you have a full list of sites you are considering to target for your link building efforts, you can paste this link in the section below the “Find new keywords” section that you see above, under “Get metrics and forecasts for your keywords,” like so:
This will list traffic for each of the brand names. You can sort them by highest traffic by clicking on the
“Historical Metrics” tab and clicking the “Avg. monthly searches” column header:
This is a powerful way to prioritize your options, especially if you’ve already used more conveniently accessible link metrics to narrow down your targets.
Alexa Rank And Traffic Estimates
Alexa scores are the closest thing we have, to an estimate of how often the sites are used. The information comes from a global sample of millions of internet users using one of many browser extensions, cross-referenced with the data of sites that track all of their traffic using Alexa scripts. While it isn’t a perfect estimate of the amount of traffic a site gets, it seems to be more accurate than it was in the past, and is analogous or arguably better than Google’s keyword data, depending on who you ask.
To get Alexa rankings for a site you are interested in, go the Alexa.com and scroll near the bottom of the homepage, to the “Browse Top Sites” section:
There will also be a text box that says “or search for a site,” which we have entered “example.com” into, above. Click “Find” and you will be taken to a page like this:
Here you will be able to see the site’s “Global Rank.” Please keep in mind that rankings beyond 100,000 shouldn’t be considered statistically meaningful.
The lower the Alexa ranking, the better. The most popular site (Google, as you might have guessed) is ranked #1.
Clicking “Browse Top Sites” instead of performing a search will take you to this page:
These are some of the best metrics you can find anywhere; unfortunately, you can only get them for the top 500 sites unless you sign up for $99 per month. This will give you access to specific traffic figures and several user behavior metrics that can tell you a lot about how people are interacting with the site. User behavior metrics, tell you if people are actually using the site and can be a halfway decent proxy for the click-through rate that you can expect from a link on the site.’’
This is all good data to have, but the Alexa ranking alone can be enough to make a judgment call.
The Google Ranking Itself
This might seem like an obvious and frivolous point to include, but I believe that the position a page ranks in Google for its target keywords is one of the most important metrics to consider. We overestimate our ability to gauge the SEO value of a page, based on factors that we crawl and compile ourselves, but Google is already telling us which pages it thinks are most important for which searches, by its very nature.
Never let other link metrics throw you off, of this most crucial point. Google may actually penalize a site with great “Page Authority”. This is an extreme example, but it should be instructive.
Now, I want to be a bit more useful here, than simply recommending you to consider the top pages, you come across in your searches. The kind of searches you come across when you are building an outreach list tends to be quite different from the kind of searches that most people will be using to find pages. Just because a page ranks well for the keyword “SEO guest post” doesn’t mean it’s actually going to turn up in the kinds of searches normal people will be conducting.
I’m about to recommend a fairly evolved process, but you may find that it can be too cumbersome or too picky. If that’s the case, you can simply try opening an incognito window and Google the titles of some of the pages on the site you are interested in. If they show up in the number one position, you can consider them to have “passed” the test. If they aren’t showing up in the first position for an exact search of their title, they don’t have a lot of authority with the search engines.
If you want to be a bit more exclusive with the sites that “pass,” here is another procedure.
Separately from creating a list of potential outreach targets, take your target site’s homepage URL to the Google Keyword Planner and paste the URL into the “Find new keywords” bar:
Choose “This page only” from the dropdown menu (“Entire site” rarely works) and then click the “get started” button.
Make sure that the results are sorted by relevance, and copy the first keyword from the list in that column:
Now just paste the keyword into Google (preferably in an incognito window so that your search history doesn’t influence the results) and run a search. Repeat this for a few of the top recommendations. If you don’t come across your target site within the first page of the search results for any of them, you may want to reconsider if they are a valid target.
To be fair, this is a pretty harsh way to judge a site, especially if the keywords in question are competitive. For something a bit more forgiving, try identifying their most successful pages and see how those are doing. You can do this by taking the site URL to the Moz Open Site Explorer:
After clicking the “Search” button, click on “Top Pages” in the left navigation:
Make sure the results are sorted by “Page Authority,” then check the first few top pages in the same way we tested the homepage, above. If you can find a first-page listing for any of them it depicts that the site does fairly well at ranking in the search results, and shouldn’t be discarded.
If you have SEMrush, you can repeat this procedure for those pages on the site that have the most estimated traffic from “Traffic Analytics” in their left navigation, under the “Domain Analytics” section.
Metrics For Competitive Link Research
As I said above, the metrics above are the best in terms of evaluating the quality and durability of a link. Aside from any heuristic information you can gather in your research to make judgment calls, they are the best proxies for strong brands and referral traffic potential, which are central to a long-term successful SEO strategy.
However, they are certainly not the most convenient metrics to use when you are involved in competitive link analysis, such as scoping out competitor’s links, or otherwise dealing with large data sets.
When your goal is to narrow down a large list of options quickly, you will need to rely on the native metrics constructed by companies like Moz, Ahrefs, and SEMrush.
Domain Authority is the name of a metric developed by Moz, but the term has been adopted by the SEO community, to refer to the overall ability of a domain to rank.
It’s important to keep in mind that Google doesn’t actually employ any ranking factor called “domain authority” and evidently doesn’t use one like it either. Jon Mueller has directly confirmed this:
“We don’t have anything like a website authority score.”
Kyle Roof has also run SEO experiments with orphaned pages (pages without any links from the rest of the site) and demonstrated that they don’t inherit any authority from the main site.
With this information in mind, you might be wondering why Domain Authority could be considered a valuable metric at all.
The answer is that, while page level link metrics are the closest to what Google is actually using when they evaluate the rank-worthiness of a page, in most cases there is no way to know what those page level metrics are going to be, once a link is placed.
If you can control the exact URL of the link you are obtaining, there is a good chance you are running afoul of Google’s guidelines on link schemes, which state:
“Additionally, creating links that weren’t editorially placed or vouched for by the site’s owner on a page, otherwise known as unnatural links, can be considered a violation of our guidelines.”
Of course, there are some circumstances where a link can be placed editorially and you have some influence over which URL it is placed on, such as when you contact a webmaster about a broken link or a resource list, and recommend your link as an optional placement. In those circumstances, page-level authority metrics are the ones you should be relying most heavily on.
But, in most cases, your outreach efforts will have more vague outcomes. They may lead to guest posts, in which case you have no idea what the page level authority metrics will be, or they might be more general cross-promotional efforts and brand-awareness efforts, in which case the position or even existence of a link as a result of the outreach is ambiguous.
In those circumstances, domain authority is a proxy for the backlink value of the entire domain, which has an implicit connection to the value of the internal links on the site, as well as the likelihood that any given page will earn backlinks from those other domains.
Domain level metrics don’t mean quite the same thing for different tools. Ahrefs Domain Rating and SEMrush Domain Score are calculated in a similar way to Google PageRank, except on the domain level instead of the page level. PageRank is essentially an estimate of the probability that somebody would land on your page if he/she randomly clicked through links on the web, so these domain metrics are estimates of the likelihood that somebody would land on a domain if they randomly clicked links on the web.
What this means is that it isn’t just the total number of links that matter, but also the number of links pointing to those links, and so on.
Moz Domain Authority also incorporates the “link distance” of a domain from a trusted site (MozTrust) as well as various other factors, and then uses a machine-learning algorithm to match those factors to a prediction of rankings.
SEMrush also uses a metric called “Trust Score” based on links from trusted websites. It can be evaluated on the domain level or the page level.
Page authority resembles domain authority, except for it being applied to individual pages rather than to the site as a whole.
Moz Page Authority and Ahrefs URL Rating both incorporate a PageRank-like algorithm as well as other trust factors, to make a prediction of the probability that an individual page will rank well, irrespective of the actual keywords on the page.
SEMrush Page Score is essentially a PageRank proxy, and it also has a “Trust Score” that can be evaluated on the page level.
As we mentioned above, page level link metrics are more closely related to the actual factors that Google uses to rank web pages. PageRank itself is a direct ranking factor, and the proxies for it employed by all the major tools can be a good substitute for it. The other trust factors incorporated into these algorithms are not used directly by Google, but most SEO professionals agree that proximity to trusted sites is, if not a factor used by Google, at least a good proxy for the trust factors they do use.
Which Domain and Page Authority Metrics Should You Use?
Before discussing this, if there is only enough room in the budget for Moz, Ahrefs, SEMrush, or an alternative, I would not be willing to recommend one over the others on their link metrics alone. You will need to make a decision based on the other features these tools have to offer. None of these link metrics have a correlation with rankings higher than 40 percent, so despite the fact that they are incredibly helpful, it is not as though any of them is going to be able to guarantee that specific actions will result in a specific ranking outcome.
With that in mind, in my opinion, Ahrefs currently offers the best metrics.
There are two primary reasons for that. First, according to a third party study by Imperva, their crawler bot is the second most active crawler after Google itself, outperforming even Bing and Yahoo:
Second, the Ahrefs URL Rating has a 40 percent correlation with rankings, while Moz Page Authority has a 37 percent correlation with rankings. While I fully admit that this difference is small enough that the practical implications are negligible, it would also be dishonest to call it a tie.
Of those two factors, the crawl rate is the one that has the most practical impact. Moz more frequently fails to return Page Authority for a page, which makes fewer comparisons possible.
Since page level link metrics are the most accurate indicators of the value of a link, I would not consider domain level metrics as strongly, in choosing between tools.
I do want to reiterate here that for the most popular SEO tools (including Majestic as well as the other three discussed), from a practical standpoint, the differences in value between the metrics themselves are close to negligible. Please consider the other features and the user interfaces in order to select the tool that works best for your needs.
How To Compare Link Metrics
Whether you are building an outreach list or engaging in competitive link research, you will need to be able to compare link metrics quickly in order to narrow down which contacts you will want to consider or which strategies you want to reverse engineer.
Comparing Link Metrics In Moz
Moz’s “Compare Link Metrics” view
Moz Open Site Explorer allows you to compare link metrics for up to five URLs. Do try this, start by entering your primary URL:
Select “Compare Link Metrics” from the left navigation:
Now click the “Add URL” button on the resulting page:
From here, you can enter up to four additional URLs. They can be different URLs from different sites, or the same site, or both. Hit “Submit” after you have entered the URLs:
From here, you can compare link metrics side by side:
Comparing Link Metrics While Researching Outreach Targets
Realistically, you won’t typically be selecting outreach targets using the Moz “compare link metrics” option in most cases. It’s typically easier to grab the information as you go using Mozbar, a browser plugin.
You can use Mozbar free, but you will need to create a Moz account in order to use the tool. Once you
have it set up, you will see search results that look like this:
The “PA” is the Page Authority and the “DA” is the Domain Authority. Clicking link analysis will take you to the full list of link metrics, as in the “Compare Link Metrics” section above.
This will allow you to make quick judgment calls about whether to pursue links from the sites you come across while you are Googling for places to guest post, find broken links, or otherwise identify link opportunities.
Mozbar also displays these metrics on pages as you browse them:
I recommend keeping a spreadsheet of interesting contacts as you come across them, with a layout similar to this:
It’s a good idea to include an additional column to include qualitative notes about why a particular option looked interesting to you.
You can also include a column for emails or other contact information; although it’s often a good idea to separate the discovery and contact gathering processes into two separate processes, since searching for contact information can bog you down, and after comparing link metrics you may later decide not to contact the site you came across.
Evaluating Feasibility Of Ranking For A Keyword
You can use the Mozbar to determine whether a keyword is “out of your league” or if it is something worth perusing in your site’s current state.
To do this, simply search for the keyword you are considering attempting to rank for and take note of the link metrics, especially the Page Authority. Then simply browse through your site with the Mozbar, to get an idea of what your typical Page Authority is. If it is comparable, there is a good chance you will be able to rank for the keyword without needing to do any link building or promotion.
If you want to be a bit more rigorous, plug the PA for each page that ranks on the front page into a spreadsheet and calculate the average. If your typical new blog post or page is higher, you can likely make it the front page, provided your site covers related topics and you don’t have any trust factors throwing you off.
If not, don’t give up yet.
Paste your site into Open Site Explorer and go to “Top Pages” in the left navigation:
Look at the Page Authority of your top pages to see if they have more Page Authority than is typical for your keyword. If so, consider adding the keyword to one of your top pages if it is a good fit there. If it isn’t, evaluate whether your top pages obtained their authority from internal links alone, or if they obtained backlinks from a strategy you are confident you can reproduce.
Comparing Link Metrics During Competitive Link Research
You can sift through your competitors’ backlink profiles using Open Site Explorer. All you need to do is plug their homepage into the tool and go to “Inbound Links” in the left navigation.
From here, you can sort by Page Authority or Domain Authority. Under ideal circumstances, the recommendation would be to sort by Page Authority, evaluate whether earning a link from the same page is a possibility, and if not, browse the site a little with the Mozbar to get an idea of the Page Authority for a typical page.
If you are more pressed for time, you can sort by Domain Authority and use it as a proxy metric for Page Authority you can expect from a typical link on the site.
Comparing Link Metrics In Ahrefs
Running a Batch Comparison Of Link Metrics For Several URLs
This very powerful feature of Ahrefs isn’t available with Moz. It allows you to evaluate a list of URLs you have had previously vetted using other methods and narrows it down to options that look the most promising to you.
Batch Analysis allows you to compare metrics for up to 200 URLs at once:
Just copy and paste a list of URLs from a spreadsheet or text document and click “Start Analysis” to get the metrics, which you can then sort by any of the metrics available, or export to a new spreadsheet.
The great thing about this is that it allows you to start by evaluating link opportunities purely in terms of things like feasibility, branding, and other qualitative considerations, without needing to concern yourself with the link metrics at first. Then, after developing a list of options, you can prioritize which options to consider first based on the link metrics, after running a batch analysis.
Keep in mind that you can simply keep refreshing this and running new batch analyses forever. There is a limit to the number of pages you can evaluate, based on the plan you sign up for with Ahrefs. Just don’t go into thinking that you’ll be able to get a sorted list of link metrics for every page on the web. It doesn’t work that way.
The Ahrefs Toolbar
Ahrefs has a browser plugin similar to Mozbar, called simply the Ahrefs SEO Toolbar. It works in essentially the same way as the Mozbar and can be used in all of the same ways discussed above. If you didn’t read the sections on “Comparing Link Metrics While Researching Outreach Targets” and “Evaluating Feasibility Of Ranking For A Keyword” in the Moz section above, make sure to give them a read for some strategic recommendations on how to use this kind of toolbar.
To make the most of those sections, you will also want to know the purpose of these options in the left navigation:
Backlinks are most useful during competitive research, in which you will be able to sort a competitor’s links by the relevant metrics. Top pages, on the other hand, is best for reviewing your own site in comparison with what is currently ranking for a keyword you are considering.
Comparing Link Metrics In SEMrush
SEMrush is most useful as a tool for identifying keyword opportunities, and this is the best way to put their link metrics to use. But first, as you can see, you can certainly use SEMrush to evaluate the link metrics of a site in a similar manner to the way you would in Ahrefs or Moz Open Site Explorer:
Similar to the other tools, SEMrush also has a browser toolbar that can be used to view page and domain link metrics.
Using SEMrush Metrics To Identify Promising Keywords
When compared to the other tools, SEMrush’s link metrics alone doesn’t really stand out. However, SEMrush has a metric that is particularly useful for the relationship between keywords and links. This metric is what you will find in their Keyword Difficulty Tool. The tool can be found in the left hand navigation under the “Keyword Analytics” section:
From here, you can paste a list of keywords into the text box:
Then press the “Show difficulty” button to see the results:
The “Difficulty, %” column is calculated by simply looking at the link metrics for pages that rank in the first 20 search results, with 0% being the easiest and 100% being the hardest.
The main issue that I face with this is that this relative scale doesn’t give you anything to compare to on its own. In order to determine whether you currently have the capability to rank for one of these keywords, simply include a keyword in your list that you are already ranking for.
Then, simply sort the keywords from least to most difficult. Anything that has a lower difficulty than the keyword you are already ranking for should be within your reach provided the keyword is topically related to the rest of your site.
Other Link Metrics To Consider
“Follow” Vs Nofollow
A no-follow link looks like this in the html for a site:
<a href=”example.com/url” rel=”nofollow”>anchor text</a>
The rel=”nofollow” attribute tells the search engines not to count the link. In other words, if the link you obtain from a site contains this, the search engines most likely will not count the link. The search engines may make exceptions in cases of nofollow links that their algorithms estimate should be followed, but in general, this is not the case, even for social media links.
You can easily check for nofollow links using this toolbar.
While the nofollow attribute is an important consideration in your outreach and link building efforts, I want to stress that any followed links you earn should be valuable enough that they would still be worth earning even if they were nofollowed. In other words, if the referral traffic and branding isn’t worth it on its own, going out of your way to earn the link is a waste of time at best, and a violation of Google’s guidelines at worst.
The existence or nonexistence of a nofollow tag should only be used in deciding between two links that are already worth it.
I also want to stress that earning nofollow links can definitely be good for your SEO, as I argued at Search Engine Land. I would not go out of my way to avoid earning nofollow links, but it would be ignorant to suggest that you should ignore this factor entirely.
Number of Linking Domains
While SEO tool metrics like Moz Page Authority, Ahrefs URL Score, and SEMrush Page Score are all better predictors of the value a link will pass than a raw count of the number of external backlinks, there is still a reason to factor this into your decisions when the apparent value of links from two options is similar.
If, for example, two pages you are interested in earning links from both have the same Page Authority, making a decision based on the number of external backlinks is a rational way to break the tie.
The reason for this is that backlinks from external sites count for more than links from the same site.
Rather than looking at the total external backlink count, however, I would recommend using the number of linking domains to break the tie.
The reason for this is that, at least according to the original PageRank algorithm, all links get counted in the same way. There is no special differentiation between internal and external links. However, as Google has evolved, it has become apparent that multiple links from the same domain have diminishing returns.
In other words, each subsequent internal link counts less than the previous internal link. The same goes for each subsequent link from an identical external domain.
If two pages have the same Page Authority, but one of them has more linking domains, it is probably the page with the most link value to offer. If nothing else, the page’s authority is likely to keep growing as it attracts more links from external domains, while the other page can only grow as fast as the domain’s overall authority.
It would be fair to argue that it’s pushing things to call this a “metric,” but it would also be negligent for me to avoid discussing relevance in a guide to measuring the value of links.
A link is relevant if it is topically related to the page that the link is placed on, and if linking to it makes sense in context.
A link to a page about how to do your taxes from a page about meditation will not be as valuable as a link from a page about finance or starting your own business.
While underestimating relevance is a big problem, I believe overestimating the need for relevance is just as common. If two pages are about the exact same topic, it doesn’t really make sense for one page to link to the other, unless it is sharing additional information that isn’t on the original page. To say that a link is relevant is not to say that they are targeting the same keyword or covering the exact same topic. It simply means that the link makes sense in context and that there is a topical relationship.
Unfortunately, no tools can measure how relevant a link is to a specific keyword and spit out a number that you can use, to decide between options. Any tool that could do so, would likely fail as a practical aid in choosing between link opportunities, since the way in which Google determines relevance is unknown.
For this reason, a subjective estimate is as good as any, such as marking in a spreadsheet how “relevant” a URL is on a scale from 1 to 10.
While Google doesn’t share internal link metrics, a wide variety of tools are available to the modern SEO that allow us to estimate the value of a linking opportunity. Putting these metrics to use, we can develop SEO strategies optimized for the best results. Keep this guide handy and refer back to it as you continue to hone your link building strategies.