What are backlinks?

To a larger degree, your backlink profile is made up of backlinks from external sites (also known as referring domains) that contribute to the overall strength, relevance and diversity of your domain’s backlink profile.

The total number of backlinks can often include many links from the same referring domain or multiple referring domains. It’s common for referring domains to link back to your content if it is relevant, authoritative or useful in some way to their own domain. In an ideal world, that’s how backlinks are accumulated; unique content that other websites want to be associated with.

Generally speaking, backlinks are considered to be a “vote” of confidence for the content that’s being linked to on your domain from outside sources.

The definition of link building

Link building is the process of acquiring hyperlinks from other websites to your own. A hyperlink (usually just called a link) is a way for users to navigate between pages on the Internet. Search engines use links to crawl the web. They will crawl the links between the individual pages on your website, and they will crawl the links between entire websites.

Not all links are deliberately built by SEOs or marketers. Many of them will be created for a range of reasons such as a journalist covering a news story and linking to a source, or a blogger who loves their new coffee machine so much that they link to the retailer who sold it to them.

Acquiring links that you didn’t ask for is the nirvana of SEO. It’s always something that you should be striving for and building towards over the long term. You do this by putting in the work to make your website link-worthy, whether that’s through a great product or aspect of your service, or via producing great content that is referenced by other websites.

Alongside this long-term approach, you can also leverage a range of link building techniques which allow you to build your authority and increase your chances of ranking well and getting traffic from organic search.

The anatomy of a hyperlink

In order to understand the importance of link building, it’s important to first understand the basics of how a link is created, how the search engines see links, and what they can interpret from them.

1. Start of link tag: Called an anchor tag (hence the “a”), this opens the link tag and tells browsers and search engines that a link to something else is about to follow.
2. Link referral location: The “href” stands for “hyperlink referral,” and the text inside the quotation marks indicates the URL to which the link is pointing. This doesn’t always have to be a web page; it could be the address of an image or a file to download. Occasionally, you’ll see something other than a URL, beginning with a # sign. These links take you to a specific section of the URL.
3. Visible/anchor text of link: This is the little bit of text that users see on the page, and on which they need to click if they want to open the link. The text is usually formatted in some way to make it stand out from the text that surrounds it, often with blue color and/or underlining, signaling to users that it is a clickable link.
4. Closure of link tag: This signals the end of the link tag to the search engines.

What does a good Backlink Profile look like?

• A natural link profile has variety.  The links come from different domains and links will have different strengths.
• To best understand your backlink profile, it makes sense to look at a few top level KPI’s such as the referring domains and IP’s, the country from where the backlink is coming from, and the Top-Level-Domain.
• There are domains which are better to receive links from than others.  These are domains that are “trusted” sources and have higher domain authority.
• For example, links from educational institutions (.edu) and government entities (.gov) tend to carry a lot of authority and indicate “trusted” content or sites to search engines.

Relevance

Google places more value on relevant backlinks because people are more likely to click on them. This is something they talk about in their “reasonable surfer” patent.

What does this mean in real terms? If a plumber has backlinks from two pages, one about cats and one about installing boilers, chances are the latter is most valuable.

This idea also plays out at the domain level.

Readers of plumbing.com are more likely to click on a link to a plumber’s website than readers of cats.com.

Authority

Backlinks from strong web pages usually transfer more “authority” than those from weak ones.

Page-level authority is something we’ve studied a few times, and we’ve found a clear relationship between it and organic traffic.

That said, backlinks from strong pages don’t always transfer more authority.

Google’s original patent states that authority is split equally between all outbound links on a web page. So if you have backlinks from two pages and one has more outbound links than the other, then, all else being equal, the link from the page with fewer outbound links transfers more authority.

Are things that simple these days? Probably not. Google has a fair number of patents describing various methods for assigning value to backlinks.

Traffic

Backlinks from high-traffic pages will usually send you more referral traffic than those from low-traffic pages. That’s obvious. The real question is whether backlinks from high-traffic pages positively affect rankings more than those from low-traffic pages?

This is a question we recently tried to answer. We took the top-ranking pages for 44,589 non-branded keywords and looked at organic traffic to the pages that link to them.

Long story short, there’s a small but clear correlation between rankings and backlinks from pages with organic search traffic. However, the sheer number of backlinks from unique websites (referring domains) and page-level authority look to be more important.

Placement

Because people are more likely to click prominently-placed links, some links on web pages likely pass more authority than others.

Bill Slawski talks about this in his analysis of Google’s updated “reasonable surfer” patent.

If a link is in the main content area of a page, uses a font and color that might make it stand out, and uses text that may make it something likely that someone might click upon it, then it could pass along a fair amount of PageRank. On the other hand, if it combines features that make it less likely to be clicked upon, such as being in the footer of a page, in the same color text as the rest of the text on that page, and the same font type, and uses anchor text that doesn’t interest people, it may not pass along a lot of PageRank.

What links mean for search engines

There are two fundamental ways that the search engines use links:

1. To discover new web pages, which they can then use in their search results
2. To help determine how well a page should rank in their results

Once search engines have crawled pages on the web, they can extract the content of those pages and add it to their indexes. In this way, they can decide if they feel a page is of sufficient quality to be ranked well for relevant keywords (Google created a short video to explain that process.) When they’re deciding this, the search engines don’t just look at the content of the page — they also look at the number of links pointing to that page from external websites, and the quality of those external websites. Generally speaking, the more high-quality websites that link to you, the more likely you are to rank well in search results.

Links as a ranking factor are what allowed Google to start dominating the search engine market back in the late 1990s. One of Google’s founders, Larry Page, invented PageRank, which Google used to measure the quality of a page based in part on the number of links pointing to it. This metric was then used as part of the overall ranking algorithm, and became a strong signal because it was a very good way of determining the quality of a page. It turned out that by incorporating this into their algorithm, Google was able to serve much more useful and relevant search results than their competitors at the time.

It was so effective because it was based upon the idea that a link could be seen as a vote of confidence about a page, i.e. it wouldn’t get links if it didn’t deserve to. The theory is that when someone links to another website, they are effectively saying it is a good resource. Otherwise, they wouldn’t link to it, much in the same way that you wouldn’t send a friend to a bad restaurant.

However, SEOs soon discovered how to manipulate PageRank and search results for chosen keywords. At this point in time, Google was far more advanced than most search engines, but was still open to manipulation because it wasn’t very good at telling the difference between a high quality link and a low quality link.

Google started actively trying to find ways to discover websites which were manipulating search results by building low quality links, and began rolling out regular updates which were specifically aimed at filtering out websites that didn’t deserve to rank due to poor links.

This has also led to Google starting to discount a number of link building techniques that previously worked well; for example, submitting your website to web directories and getting a link in return. This was a technique that Google actually recommended at one point, but it became abused and overused by SEOs, so Google stopped passing as much value from that sort of link.

Over the years, Google has actively penalized the rankings of websites who have attempted such overuse of these techniques — often referred to as over-optimization — in their link building. This stepped up a gear in 2012 with the first of many updates, which became known as Penguin. These updates targeted specific link building techniques and arguably changed link building forever. From this point forward, low-quality link building techniques could not only be a waste of time, but they could also severely damage a website’s ability to rank well in organic search results. This is why we recommend understanding Google Webmaster Guidelines and crafting strategies which won’t fall foul of them.

We don’t know the full algorithm that Google uses to determine its search results — that’s the company’s “secret sauce.” Despite that fact, the general consensus among the SEO community and recent studies have shown that links still play a big role in that algorithm.It’s generally accepted that, if all other factors are equal, the volume and quality of links pointing to a page can make the difference between rankings.

We’ve mentioned “high-quality” a few times now, and there’s a good reason: The focus on quality is increasing as Google becomes ever more sophisticated at filtering out low-quality links. This directly impacts SEOs, as you need to make sure the link building techniques you choose focus primarily on that quality.

Followed vs. nofollowed

Nofollowed backlinks don’t usually influence the linked page’s rankings—although they can.

Because link building takes time and effort, it’s best to prioritize getting followed links. Just don’t kick up a fuss if you get a nofollowed link. It may still have some SEO value.

Anchor text

Anchor text refers to the clickable words that form a backlink.

Google says that anchor text influences rankings in their original patent.

Google employs a number of techniques to improve search quality including page rank, anchor text, and proximity information.

That said, when we studied the relationship between anchor text and rankings across 384,614 pages, the correlations were weak.So while anchor text does matter, it’s not as important as other things.

 If you’re building backlinks through outreach, you won’t usually have much control over the anchor text used when linking to your site. That’s a good thing. It helps keep things natural and is also a sign that the link you’ve acquired is of a certain quality.