Link Building Metrics
There are various metrics associated with links that you should be aware of. These metrics can help you judge the value of a potential link, helping you assess whether it is worth pursuing and how much resources you should put into acquiring it. Knowing these kinds of metrics is also useful when you are doing link profile analysis (a holistic report of the number and types of links on a website), whether on a competitor's website or your own.
Domain strength
Domain strength is the cumulative value of an entire domain. Instead of looking at the value of individual pages, we look at the domain as a whole to understand how strong it is.
It is usually displayed as either Domain Authority or as the homepage's Page Authority.
PageRank is calculated by Google and based on the number and quality of links pointing to a web page. It runs on a scale from 0-10, with 10 being the highest. We can use the PageRank of a website's homepage to get an idea of how strong it is. Although technically this is only the PageRank of a single page, it is still a good indicator of the strength of a domain, because the majority of a website's links will be to the homepage and PageRank flows from there to internal pages.
It should be noted that there is a difference between "Toolbar PageRank" and the actual PageRank used by Google. Toolbar PageRank is visible to you by installing the Google Toolbar on your browser or by using a browser plugin/extension that pulls data from the same source. It is updated every 3-4 months by Google, which is different from the actual PageRank that is more fluid, constantly updated by Google to be fed into their ranking algorithm.
For that reason, the PageRank you see in the Google Toolbar could be several months old. This is why new web pages mainly have a PageRank score of 0: They need to wait for Google to update the toolbar.
Domain Authority is calculated by Moz and runs on a scale of 0-100, with 100 being the highest. It uses a number of signals taken from the Moz crawler and tries to predict how well a domain will perform in search results. It is useful alongside PageRank as another indicator of how strong a domain is.
In terms of link building, site strength is a good metric to use because you want to get links from websites that are very strong. If the links you get are from strong domains, they will pass more strength to your own website, which is a clear signal to Google that you have a good site that deserves to rank well.
For example, CNN has a PageRank of 8 and a Domain Authority of 99. Lots of other websites link to CNN because it is an authoritative website with high-quality content. Because of this, CNN is not very likely to link to low-quality websites, so if you get a link from CNN, it is a signal that you have a good website, too.
Tools for measuring domain strength
Google Toolbar for PageRank (for Internet Explorer)
Page strength
There will be occasions when you have the opportunity to get a link from a page that already exists on a website, as opposed to a new page that is created for a blog post or news item. An example could be an existing list of some kind to which your link gets added; perhaps your coffee shop is added to a page with a list of the best espresso in Seattle.
In cases like this, you should assess how strong the page is so that you know how worthwhile the link is to you before you put too much effort into acquiring it. There are two main metrics, and they are nearly identical to those for domain strength: PageRank and Page Authority.
We've already talked about PageRank. Page Authority is another Moz metric that is very similar to Domain Authority, except that it only applies to a single page rather than an entire domain.
The higher the PageRank / Page Authority of the page you want a link from, the more likely it is to help you with your SEO efforts.
Tools to measure page strength
Google Toolbar for PageRank (for Internet Explorer)
Anchor text
We've already covered the meaning of anchor text; now lets consider what it means as a metric for SEOs.
Anchor text can give Google an indication of the subject matter of the page being linked to. So if I linked to a page using the words "fitness routine," then it is likely that the page being linked to contains information about fitness routines. Google can then use this information as part of its ranking algorithms. In this case, they may decide that the page being linked to should rank higher for the keyword "fitness routine" and close variations.
For many years, having a lot of links pointing to your website that contained your keyword as the anchor text was a very good way of helping you rank well for that keyword. While this is still the case to some extent, it does appear that the strength of anchor text as a signal is diminishing slightly. This is most likely because of the over-optimisation of anchor text by SEOs and Google's readiness to penalize such websites through the Penguin update.
Rand talked about this in an episode of Whiteboard Friday and gave some indicators of what Google may use instead.
Due to the changing nature of the perception and use of anchor text, it is probably best to be cautious when building links. Try not to build too many links that have the exact same anchor text in them, particularly if the links are not of the highest quality, such as links that are from low-quality domains, non-editorial sitewide links, or links that have too much anchor text (for more details on link quality, check out this post on State of Digital). You should try to make your link profile look as natural as possible, which often means getting links that use your brand or company name as the anchor text.
Tools for measuring anchor text
Open Site Explorer - click on the "anchor text" tab
Number of links
When link building, you will obviously want to keep track of how many links you have built. You will also want to check into how your website compares to your competitors' sites to see how far (or how far ahead!) you have gotten.
As we've discussed in previous chapters and seen in surveys, the raw number of links pointing to your website is a strong ranking signal. However, you do need to remember that the quality is equally, if not more important than the number.
As a metric, number of links can be useful to us in two main ways:
1. Measuring progress / success of a link building campaign
2. For running comparisons between your website and competitors' sites
Both of these uses still need to factor in quality of links in order to be helpful to us. When we compare our number of links to a competitor's number, it can sometimes show gaps that may explain ranking differences. If you're trying to rank for the keyword "wooden tables" and the websites on the first page of results all have over over 1,000 linking domains, that gives you a solid sense for the competitiveness of that niche and the kind of attention you need to earn in order to rank among those results.
Tools for measuring number of links
Linking root domains
Not to be confused with the raw number of links, linking root domains is an even more powerful ranking signal to Google. When we say linking root domains, we mean the number of distinct domains that link to us, not the raw number of links.
For example, if CNN linked to you from five different news stories, that would be counted as five links, but only one linking root domain, since all five links came from cnn.com.
If the BBC linked to you from one news story, that would be one link and one linking root domain.
The number of linking root domains is a stronger signal than the raw number of links because it is a better indication of the true popularity of a website. If we go back to how Google think of links as "votes," then in this sense each website has only one vote to give you. No matter how many times they link to you, they still only count as one vote, which prevents the digital equivalent of "stuffing the ballot box."
Multiple links from the same domain can be the result of a number of things. Linking from multiple content pages is one way, but the most common ways are by what we call sitewide links. A sitewide link is a link that is placed in some kind of templated element of the website, such as the header, footer, or sidebar. The most common example is a "blogroll" link, as a blogroll is generally on every page of the website.
In general, these types of links are not as valuable as in-content links from just a few pages. Sitewide links can sometimes be spammy, paid for, and not editorially given in the sense that Google would like. In fact, Moz published a case study of a site that was heavily penalized by Google for incorporating sitewide links on its clients' pages. Therefore, you should treat them with caution, only get them from high-quality websites, and don't be too aggressive with your anchor text.
Tools for measuring linking root domains
Open Site Explorer - click on the "linking domains" tab
Relevance of the linking page
There has always been some debate as to whether relevance is a strong signal used by Google to calculate the value of a link. Logic tells us that it should be, because it is natural for relevant websites to link to each other. However, what if you get a link from the homepage of the BBC to your website about coffee? You wouldn't reject it just because the BBC website isn't about coffee.
If we look beyond link building for a moment though, you still want to bring targeted traffic to your website so that you can try to convert visitors into customers. For this reason alone, you should be trying to place links on websites where potential customers may visit. This means that the value of the link goes far beyond SEO and can become a source of direct income.
As discussed in the anchor text section above, there are some indications that Google is moving away from anchor text as a strong signal and, instead, could be using analysis of an entire page to attribute relevance to the link. If this proves to be the case, then getting links from relevant pages could become a strong ranking signal.
Right now, best practice should be to focus on quality to make sure you're being passed link equity and on relevance in the sense that you want to attract the right kind of traffic.
Position of links on the page
Imagine you live in Seattle and you have a blog about coffee. You're going to share a link with your readers to the website of a local coffee shop that serves the most amazing fresh coffee ever. Where would you place this link on the page?
If you really wanted your readers to see it, you'd position it somewhere obvious. Probably in the main body of the page, probably near the top of the page, and probably within some content that explains how amazing the coffee shop is.
You probably wouldn't place the link in the footer, right? Many users may not scroll down the page that far, and even if they do, they wouldn't expect to find useful links in that section.
Google is able to work out the position of a link on a page, and from this could choose to value it differently. If the link is in the footer of a page, then Google could reduce the value of that link because they assume it isn't a great link for users (otherwise, it wouldn't be hidden away in the footer).
Google can also use the position of links on a page in aggregate. For example, they could see if 50% of all the links pointing to your website are in some kind of footer. This could indicate low-quality link building, and Google may decide to take a closer look.
Another example could be if Google finds that 50% of the links pointing to your website are from sidebars. Again, on its own, this may be legitimate, but it could also be a signal to Google that you're buying links. Many link brokers will place links in the sidebar of pages as opposed to within the content.
Because of this ability, you should make sure that you are getting links from websites which are happy to link from within content wherever possible. There is nothing wrong with the odd sidebar link, but too many of them does not signal a good link profile.
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