Posted by Cyrus-Shepard
Links matter for SEO. A lot.
Most marketers understand that links to websites count as “votes” on the web. Google — and other search engines — use these votes to rank web pages in search results. The more votes a page accumulates, the better that page’s chances of ranking in search results.
This is the popularity part of Google’s algorithm, described in the original PageRank patent. But Google doesn’t stop at using links for popularity. They’ve invented a number of clever ways to use links to determine relevance and authority — i.e. what is this page about and is it a trusted answer for the user’s search query?
To rank in Google, it’s not simply the number of votes you receive from popular pages, but the relevance and authority of those links as well.
The principals Google may use grow complex quickly, but we’ve included a number of simple ways to leverage these strategies for more relevant rankings at the bottom of the post.
“Thus, even though the text of the document itself may not match the search terms, if the document is cited by documents whose titles or backlink anchor text match the search terms, the document will be considered a match.”
In a nutshell, if a page links to you using the anchor text “hipster pizza,” there’s a good chance your page is about pizza — and maybe hipsters.
If many pages link to you using variations of “pizza”— i.e. pizza restaurant, pizza delivery, Seattle pizza — then Google can see this as a strong ranking signal.
(In fact, so powerful is this effect, that if you search Google for “hipster pizza” here in Seattle, you’ll see our target for the link above ranking on the first page.)
Volumes could be written on this topic. Google’s own SEO Starter Guide recommends a number of anchor text best practices, among them:
While some Google patents discuss ignoring links with irrelevant anchor text, other Google patents propose looking at the text surrounding the anchor text for additional context, so keep that in mind.
A word of caution: While optimizing your anchor text is good, many SEOs over the years have observed that too much of a good thing can hurt you. Natural anchor text on the web is naturally varied.
Over-optimization can signal manipulation to Google, and many SEOs recommend a strategy of anchor text variety for better rankings.
In the early days of Google, not long after Larry Page figured out how to rank pages based on popularity, the Hilltop algorithm worked out how to rank pages on authority. It accomplished this by looking for “expert” pages linking to them.
An expert page is a document that links to many other topically relevant pages. If a page is linked to from several expert pages, then it is considered an authority on that topic and may rank higher.
A similar concept using “hub” and “authority” pages was put forth by Jon Kleinberg, a Cornell professor with grants from Google and other search engines. Kleinberg explains:
“…a good hub is a page that points to many good authorities; a good authority is a page that is pointed to by many good hubs.”
– Authoritative Sources in a Hyperlinked Environment (PDF)
While we can’t know the degree to which these concepts are used today, Google acquired the Hilltop algorithm in 2003.
A common practice of link builders today is to seek links from “Resource Pages.” These are basically Hub/Expert pages that link out to helpful sites around a topic. Scoring links on these pages can often help you a ton.
Additional Resources: Resource Page Link Building
All links are not created equal.
The idea behind Google’s Reasonable Surfer patent is that certain links on a page are more important than others, and thus assigned increase weight. Examples of more important links include:
Conversely, less important links include:
Because the important links are more likely to be clicked by a “reasonable surfer,” a topically relevant link can carry more weight than an off-topic one.
“…when a topical cluster associated with the source document is related to a topical cluster associated with the target document, the link has a higher probability of being selected than when the topical cluster associated with the source document is unrelated to the topical cluster associated with the target document.”
– United States Patent: 7716225
The key with leveraging Reasonable Surfer for SEO is simply: work to obtain links that are more likely to get clicked.
This means that you not only benefit from getting links from prominent areas of high-traffic pages, but the more relevant the link is to the topic of the hosting page, the more benefit it may provide.
Neither page topics/anchor texts have to be an exact match, but it helps if they are in the same general area. For example, if you were writing about “baseball,” links with relevant anchor text from pages about sports, equipment, athletes, training, exercise, tourism, and more could all help boost rankings more than less relevant links.
Despite rumors to the contrary, PageRank is very much alive and well at Google.
PageRank technology can be used to distribute all kinds of different ranking signals throughout a search index. While the most common examples are popularity and trust, another signal is topical relevance, as laid out in this paper by Taher Haveliwala, who went on to become a Google software engineer.
The original concept works by grouping “seed pages” by topic (for example, the Politics section of the New York Times). Every link out from these pages passes on a small amount of Topic-Sensitive PageRank, which is passed on through the next set of links, and so on.
In the example above, 2 identical pages target “Football”. Both have the same number of links, but the first one has more relevant Topic-Sensitive PageRank from a linking sports page. Hence, it ranks higher.
The concept is simple. When obtaining links, try to get links from pages that are about the same topic you want to rank for. Also, get links from pages that are themselves linked to by authoritative pages on the same topic.
Phrase-based indexing can be a tough concept for SEOs to wrap their heads around.
What’s important to understand is that phrase-based indexing allows search engines to score the relevancy of any link by looking for related phrases in both the source and target pages. The more related phrases, the higher the score.
In the example below, the first page with the anchor text link “US President” may carry more weight because the page also contains several other phrases related to “US President” and “John Adams.”
In addition to ranking documents based on the most relevant links, phrase-based indexing allows search engines to consider less relevant links as well, including:
Beyond anchor text and the general topic/authority of a page, it’s helpful to seek links from pages with related phrases.
This is especially helpful for on-page SEO and internal linking — when you optimize your own pages and link to yourself. Some people use LSI keywords for on-page optimization, though evidence that this helps SEO is disputed.
Local inter-connectivity refers to a reranking concept that reorders search results based on measuring how often each page is linked to by all the other pages.
To put it simply, when a page is linked to from a number of high-ranking results, it is likely more relevant than a page with fewer links from the same set of results.
This also provides a strong hint as to the types of links you should be seeking: pages that already rank highly for your target term.
Quite simply, one of the easiest ways to rank is to obtain topically relevant links from sites that already rank for the term you are targeting.
Oftentimes, links from page 1 results can be quite difficult to obtain, so it’s helpful to look for links that:
If the above concepts seem complex, the good news is you don’t have to actually understand the above concepts when trying to build links to your site.
To understand if a link is topically relevant to your site, simply ask yourself the golden question of link building: Will this link bring engaged, highly qualified visitors to my website?
The result of the golden question is exactly what Google engineers are trying to determine when evaluating links, so you can arrive at a good end result without understanding the actual algorithms.
Above all else, try to build links that bring engaged, high-value visitors to your site.
If you don’t care about the visitors a link may bring, why should Google care highly about the link?
Consider this advice when thinking about links for SEO:
Finally, DO try to earn and attract links to your site with high quality, topically relevant content.
Big thanks to Bill Slawski and his blog SEO by the Sea, which acted as a starting point of research for many of these concepts.
What are your best tips around topically relevant links? Let us know in the comments below!
Note: A version of this post was published previously, and has since been substantially updated. Big thanks to Bill Slawski and his blog SEO by the Sea, which acted as a starting point of research for many of these concepts.
Sign up for The Moz Top 10, a semimonthly mailer updating you on the top ten hottest pieces of SEO news, tips, and rad links uncovered by the Moz team. Think of it as your exclusive digest of stuff you don’t have time to hunt down but want to read!