Link Types


Glossary  |  4 mins

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Backlinks, sometimes referred to as inbound links or incoming links, are links from one domain to another. In the context of SEO, backlinks are seen by Google as a “vote of confidence” that tells its algorithm that the page being linked to is associated or has value. Because pages with a higher number of quality backlinks tend to enjoy higher rankings, a solid backlink building strategy is an essential component for any SEO project.

Backlinks are important because they tell search engine algorithms that a page is credible and valuable to users. The more legitimate, quality backlinks a site has, the higher it will rank for various search terms on search engine result pages (SERPs). Because of this, SEO professionals and SEO tools place great stock in the quality of backlinks a site has, and use this as a primary indicator for its ranking potential.

This method of ranking pages based on the “votes of confidence” they gain through links is a cornerstone of Google’s PageRank algorithm, and was first set out in a 1998 whitepaper The PageRank Citation Ranking: Bringing Order to the Web. Google has made countless changes to its ranking algorithm since then, and although additional factors are certainly important, backlinks remain a major predictor of how well a site or page will perform in Google’s rankings.

Though there was a time when any link from any referring domain would improve a target site’s ranking, today backlinks exist on a stricter spectrum of value. This means that if you want to improve your site’s rankings through link building, your focus needs to be on high-quality, relevant backlinks.

The quality of a backlink is determined by a range of factors.

One of the most important is how trustworthy and authoritative the website hosting the link is. A link from the BBC News website, for example, will carry a lot more weight in the eyes of a search engine compared with a brand new site that has no authority whatsoever. This is because the BBC News domain is an authority, with a much bigger history of powerful backlinks and has very high levels of trust (through global traffic and consistent interaction of users, amongst many other key factors). The brand new website in this analogy has no such history or trust, and therefore no such credibility to be offering value as a backlink.

Another big factor is the context of the link within the content, and within the page itself. The use of anchor text plays an important role, and whereabouts on the page the link is placed. Google’s Penguin algorithm update included a filter that prevents rankings being manipulated by black hat link building tactics, including keyword stuffing and overuse of exact match anchor text, to reduce the benefit that was once provided by such underhand tactics.

The subject matter of a referring domain and a specific page that hosts a backlink will also have a big impact on the value of a link. When Google can see that a given backlink is topically relevant based on the content of the referring URL, it will see that link as carrying more weight than otherwise. For example, if a site that covers professional golf news links to a site that sells golf accessories, it will likely prove much more valuable than a link from a site about investment and personal finance. This is topical relevance, and is especially pertinent when considering which page is being linked to, AKA the deep links of the domain being referred.

It has long been understood that links from domains that haven’t previously linked to your domain are superior. Whilst this is still likely the case, it is also a very good trust signal to receive multiple links from the same domain, especially to different pages on your domain. Your backlink profile will always have more backlinks than referring domains, so it would therefore make sense that you might wish the most powerful referring domains to be linking multiple times.

Backlink acquisition can take many forms, though the longest standing and most white hat of the lot is to create high value content on your own website, which will then act as a linkable asset. This can be any piece of content; blog posts, infographics, videos or tools that provide value to a given target audience, and encourages people to link to it naturally. In this way, linkable assets give webmasters a passive method of creating backlinks for SEO, that will accrue value without requiring ongoing work. This emphasis on hosting linkable assets is the primary reason why the marketing disciplines of SEO and content marketing are so closely linked.

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Backlinks FAQs

Are backlinks important for SEO?

Backlinks are exceedingly important for SEO, as Google uses them as an indicator for how valuable a site is in the eyes of web users, and therefore how high it should be ranked on a given page of search results.

What makes a good backlink?

The quality of a backlink is determined by a range of factors, such as the authority and topical relevance of the referring domain, the age of the link, and the presence of keywords in a link’s anchor text. Other factors such as whether or not a referring domain has linked to the target site in the past can also influence the value of a link.

Questions to ask your link builder