What Are Backlinks and Why Do They Matter for SEO?

A backlink is a link from someone else’s website to yours. That is really all it is.

If a food blogger writes about their favourite kitchen tools and links to your product page, that is a backlink. If a news site quotes your research and links to your article, that is a backlink. If a forum post recommends your service and includes your URL, that is a backlink too.

They sound simple, but they happen to be one of the most important factors in whether your pages rank on Google.

Why does Google care about backlinks?

When Larry Page and Sergey Brin built the original Google algorithm at Stanford in 1996, their central insight was that a link from one website to another is a form of endorsement. Their paper, “The Anatomy of a Large-Scale Hypertextual Web Search Engine,” described this as “PageRank” and it became the foundation of how Google worked.

Nearly 30 years later, Google still operates on this logic. Its algorithm treats backlinks as third-party votes for your content. A page with many good-quality backlinks tends to outrank a page with none, even when the content quality is similar.

In 2023, a leaked Google document known as the “Google API Content Warehouse” leak confirmed that backlinks remain a core signal in Google’s ranking systems, despite years of speculation that Google was moving away from them.

Think of it like academic papers. A research paper cited by a hundred other papers is probably more important than one nobody references. Google applies the same logic to websites.

Not all backlinks are equal

A link from the BBC carries far more weight than a link from a random blog with three posts and no readers. Google measures link quality through PageRank, which considers the authority of the linking site and how many other links are competing for that same authority.

Here is what makes a backlink valuable:

Authority of the linking site. A link from a well-established, trusted website passes more value than one from a new or low-traffic site. Ahrefs measures this as Domain Rating (DR); Semrush uses Authority Score. Both are proxies for how much trust Google has built up for that domain over time.

Relevance of the linking site. A backlink from a site in your niche is worth more than one from a completely unrelated industry. If you run an accounting firm and a major finance publication links to you, that is strong. If a gaming website links to you, it is much weaker, and in some cases Google may discount it entirely.

The anchor text used. Anchor text is the clickable words in the link. “Click here” tells Google very little. “Best accounting software for freelancers” tells Google a lot about what your page covers.

Where on the page the link appears. A link in the main body of an article carries more weight than one buried in a footer or sidebar. Google has confirmed it evaluates link placement as part of how it weighs a link’s importance.

Whether the link is followed or not. A dofollow link passes authority to your site. A nofollow link includes a tag telling Google not to pass PageRank. Nofollow links still have value because they drive traffic and a natural backlink profile includes a mix of both.

What does the research actually say about backlinks and rankings?

Ahrefs studied over 1 billion pages in 2020 and found that 90.63% of pages get zero organic traffic from Google, and the leading factor separating them was the absence of backlinks. Pages with more referring domains consistently ranked higher and attracted more traffic.

Backlinko’s analysis of 11.8 million Google search results found that the number-one result on Google has an average of 3.8 times more backlinks than results in positions 2 through 10.

SparkToro and Moz’s annual “State of the Algorithm” surveys have consistently shown that link signals remain one of the top three ranking factors even as Google’s algorithm has evolved to include more content quality and user experience signals.

A real example of backlinks changing rankings

In 2017, the team at Siege Media ran a case study on a client in the home services space. The site had decent content but almost no backlinks. Over six months, they built 40 high-quality links from relevant home improvement publications and directories. Organic traffic increased 300%. Rankings for the client’s primary keywords moved from page 4 to page 1.

The content did not change. The technical setup did not change. The backlinks were the variable.

What makes a bad backlink?

Not every backlink helps you. Some can actively hurt your rankings.

Links from sites that exist purely to sell links, links from unrelated spam sites, links with over-optimised anchor text where every link pointing to you uses the exact same keyword phrase, and large volumes of links appearing suddenly and artificially all send negative signals to Google.

Google’s Penguin algorithm, launched in 2012 and now running in real time as part of the core algorithm, specifically targets manipulative link building. If your site has a history of spammy links, you can use Google’s Disavow Tool to tell Google to ignore them.

The safe test: if a link would make sense to a human reader and comes from a real site with real content, it is probably fine. If it exists only for SEO purposes, it is probably not.

How many backlinks do you need to rank?

There is no fixed number. It depends entirely on how competitive your target keyword is.

For a low-competition keyword in a niche industry, you might rank with three or four good backlinks. For a high-competition keyword where every result in the top 10 comes from established websites with thousands of links, you would need significantly more.

The right approach is to check what the top-ranking pages for your target keyword already have in terms of backlinks using a tool like Ahrefs or Semrush, and use that as your benchmark. You are not trying to hit a number. You are trying to be competitive with whoever already ranks.

How do you build backlinks?

The most reliable ways to earn backlinks are:

Creating content worth linking to. Original research, free tools, and data that other writers cite as sources attract natural links without outreach. This is the highest-leverage long-term approach.

Guest posting. Writing articles for other sites in your niche, with a link back to your site in the content or author bio.

Broken link building. Finding broken links on other websites and offering your content as a replacement.

Digital PR. Getting your data or research cited in news articles and publications.

Being a source for journalists. Platforms like HARO connect journalists with expert sources, and quotes typically come with a link from a news publication.

For a full walkthrough of free methods that work for new sites, see how to get backlinks for free.

How do you check your backlinks?

Google Search Console shows you your backlinks for free. Go to the Links section to see which sites link to you and which of your pages have the most links.

For more detail, including the authority scores of linking sites and your competitors’ backlink profiles, Ahrefs, Semrush, and Moz all offer free tiers with limited monthly checks. Enough to track progress when you are starting out.

Frequently asked questions