What Are Backlinks and Why Do They Matter for SEO

A backlink is a link from someone else's website to yours. That's it. That's the entire concept. One site links to another site, and the link pointing toward you is your backlink. People sometimes call them inbound links or incoming links, and occasionally you'll see them referred to as external links (from the perspective of the site doing the linking), but they're all describing the same thing. Site A links to Site B, and Site B just got a backlink.

I know that sounds almost too simple, and honestly, the core idea really is that straightforward. But the reason this simple concept has spawned an entire industry, countless tools, and endless debates in SEO forums is because of what backlinks mean to search engines. Google, from its earliest days, treated links between websites as votes of confidence. If a reputable site links to your page, Google reads that as a signal that your page probably has something worthwhile on it. The more of those signals you collect, the more Google trusts your site, and the higher you tend to rank.

The original algorithm behind this idea was called PageRank, named after Larry Page. It was essentially an academic citation model applied to the web. In academia, a research paper that gets cited by hundreds of other papers is generally considered more important than one nobody references. PageRank took that same logic and said: a webpage that gets linked to by hundreds of other webpages is probably more important than one with zero links pointing to it. The math was more involved than that, of course, incorporating things like the authority of the linking page and the total number of outbound links on that page, but the fundamental insight was beautifully simple.

Now, Google has confirmed many times that their algorithm uses hundreds of ranking factors. And they've also evolved way beyond the original PageRank formula. But links continue to be one of the top signals. In various SEO industry studies — the kind Ahrefs and Semrush publish every year or so — the correlation between the number of referring domains pointing to a page and that page's ranking position remains strong. Not perfect, because correlation and causation are different things and there are pages ranking with very few backlinks in less competitive niches. But strong enough that no serious SEO professional ignores link building. Our article on Anchor Text Optimization: Best Practices and Common Mistakes explores this idea in more depth.

Not All Backlinks Are Created Equal

Here's where things get a bit more nuanced. A link from the New York Times carries far more weight than a link from your cousin's abandoned Blogspot site. This shouldn't surprise anyone. If you think about the citation analogy again, a mention in a prestigious journal means more than a mention in a random newsletter with twelve subscribers. Search engines evaluate links based on a bunch of different quality signals, and understanding those signals is where backlink strategy actually starts to get interesting.

The authority of the linking domain matters a lot. Tools like Ahrefs have their Domain Rating (DR) metric, Moz has Domain Authority (DA), and Semrush uses Authority Score. None of these are Google's actual metrics — Google doesn't share its internal authority scores publicly — but they're reasonable proxies based on each tool's analysis of the web's link graph. A link from a DR 85 site is generally going to move the needle more than a link from a DR 12 site. Generally. I want to be careful about speaking in absolutes here because I've seen exceptions. I've seen a single link from a highly relevant niche site with modest authority metrics outperform links from big generic sites. Relevance plays a role too.

Speaking of relevance. If you run a website about organic gardening and you get a backlink from a well-known gardening publication, that's probably more valuable than a link from a high-authority tech blog that happened to mention your site in passing. Google's gotten much better at understanding topical relevance over the years, and a link that makes contextual sense — where the content of the linking page is related to the content of your page — tends to carry more weight. The data on this is mixed, and I'm not sure anyone outside of Google knows exactly how much topical relevance factors into the equation versus raw authority, but the general consensus among practitioners is that it matters and it's been mattering more over time.

Then there's the distinction between dofollow and nofollow links. By default, all HTML links are dofollow, meaning search engine crawlers will follow them and pass along ranking value (sometimes called "link juice," a term I've always found slightly gross but it stuck). In 2005, Google introduced the rel="nofollow" attribute, originally to combat comment spam. When a link has the nofollow attribute, it's essentially a signal to Google saying "I'm linking to this page but I don't necessarily vouch for it." Google traditionally didn't pass PageRank through nofollow links.

But — and this is important — in 2019, Google changed how they handle nofollow. They announced that nofollow would become a "hint" rather than a directive. This means Google might choose to crawl, index, and even pass some value through nofollow links if they determine the link is genuinely useful. They also introduced two new attributes: rel="sponsored" for paid links and rel="ugc" for user-generated content links. In practice, most SEOs still consider dofollow links more valuable than nofollow ones, and that's probably fair. But the binary "nofollow links are worthless" take that you used to hear everywhere isn't really accurate anymore. A nofollow link from a major publication still sends traffic, still builds brand awareness, and might even pass some ranking value now. There's plenty more to dig into, and 10 Proven Link Building Strategies That Work is a great place to start.

Anchor text is another factor. The clickable text of a link gives Google contextual information about what the linked page is about. If fifty different websites link to your page using the anchor text "best running shoes for flat feet," Google takes that as a pretty strong signal about your page's topic. But over-tweaked anchor text can actually trigger penalties. If every single backlink to your site uses the exact same keyword-rich anchor text, that looks unnatural. Real, organic link profiles have a messy mix of branded anchors (your company name), naked URLs, generic phrases like "click here" or "this article," and yes, some keyword-rich anchors sprinkled in. When I pull up a site's backlink profile in Ahrefs and I see that 80% of their anchors are exact-match keywords, that's a red flag. Either they've been doing aggressive link building or someone's doing negative SEO against them.

How Backlinks Actually Influence Rankings

Let me walk through the mechanics a bit more concretely, because I think people sometimes treat backlinks as this abstract concept without really understanding the chain of events.

When another website links to one of your pages, here's roughly what happens from an SEO perspective:

1. Google's crawlers discover the link on the external page. This can happen quickly if the linking site is crawled frequently, or it might take weeks if it's a smaller site that Google doesn't visit often.
2. The crawler follows the link to your page and registers that there's a new backlink in your link profile. Google processes this information and updates its index accordingly, though the timing is unpredictable.
3. The link contributes to your page's overall authority calculation. How much it contributes depends on all those factors we discussed — the linking site's authority, relevance, the anchor text, whether it's dofollow, the placement on the page (a link in the main body content is generally valued more than one buried in a footer or sidebar), and more.
4. Your page's updated authority score gets factored into its ranking for relevant search queries. If the additional authority pushes you above a competitor for a given keyword, you might see a ranking improvement.
5. Higher rankings mean more organic traffic. More traffic means more people see your content, some of whom might link to it naturally, creating a positive feedback loop.

That feedback loop is real and it's one of the reasons why link building can have compounding returns. The rich get richer, so to speak. Pages that already rank well get more visibility, which leads to more natural backlinks, which reinforces their rankings. This is also why it can feel so hard to break into competitive niches from scratch — you're trying to compete against pages that have been accumulating links for years.

I should mention that the impact of a single backlink varies enormously depending on your current situation. If your site has zero backlinks and you acquire one from a decent authority site, that single link might produce a noticeable ranking jump. If your site already has thousands of backlinks from hundreds of referring domains, one additional link is unlikely to move the needle in any measurable way. There are diminishing returns, and the marginal value of each new link decreases as your link profile grows. This is something I see newer SEOs misunderstand sometimes. They'll obsess over acquiring one specific link from one specific site, when in reality their time would be better spent building twenty links from twenty different domains of moderate authority. For a deeper look at this topic, see our guide on How Many Backlinks Do You Need to Rank on Google?.

The referring domains metric is worth dwelling on. It's not just about the total number of backlinks — it's about how many unique websites those links come from. A hundred links from a single domain is far less valuable than one link each from a hundred different domains. Google wants to see that a diverse range of websites are vouching for you, not just one site that happens to link to you from every page. When I'm auditing a site's backlink profile in Google Search Console or Ahrefs, the referring domains count is often more informative than the raw backlink count.

The Messy Reality of Getting Backlinks

Alright, so backlinks matter. A lot. That much is clear. The harder question is how you actually get them, and this is where the SEO industry fractures into different camps with strong opinions.

There's the "build great content and they will come" camp. The idea here is that if you create genuinely useful, original, well-researched content, people will naturally discover it and link to it. This is... partially true. I've seen it work. I've also seen incredible content sit at zero backlinks for months because nobody knew it existed. Creating something worth linking to is necessary but not sufficient. You usually need to do some kind of outreach or promotion to get eyeballs on your content in the first place, especially if your site doesn't already have an established audience.

Then there's manual outreach. This is the bread and butter of most link building campaigns. You identify sites that might be interested in your content, you reach out to the site owners or editors, and you pitch them on why linking to your page would be valuable for their readers. This can take many forms: guest posting, broken link building (finding dead links on other sites and suggesting your content as a replacement), resource page link building, the skyscraper technique (creating something better than what currently ranks and telling people who linked to the inferior piece about your superior version), and dozens of other strategies. Manual outreach is time-consuming and often has low response rates. Most people who've done it will tell you that a 5-10% response rate is decent, and the actual link acquisition rate is even lower.

There's also the murkier world of paid links, link exchanges, and PBNs (private blog networks). Google's guidelines directly state that buying or selling links that pass PageRank violates their policies. And they've gotten much better at detecting these patterns over the years. The Penguin algorithm update in 2012 was specifically designed to target manipulative link building, and it decimated a lot of sites that had been relying on low-quality link schemes. That said, paid link building still happens at scale. Some people get away with it indefinitely. Others get caught and penalized. It's a risk-reward calculation, and I'd generally steer people away from it, especially for sites they care about long-term. But I'm also not going to pretend it doesn't exist or that nobody does it successfully. If this is new to you, Understanding Link Equity: A Complete Guide breaks it down step by step.

Digital PR has emerged as one of the more effective and sustainable link building approaches in recent years. This involves creating newsworthy content — original research, surveys, data studies, interactive tools, provocative takes — and pitching it to journalists and publications. When a journalist writes about your study and links to it as the source, that's a high-quality editorial link that's very hard for Google to discount. The links you get from digital PR campaigns tend to be from high-authority news sites, and they tend to be editorially given, which is exactly the kind of link Google wants to reward.

One thing that's worth noting: link building velocity matters too. If your site goes from getting two backlinks per month to getting two hundred per month overnight, that can look suspicious to Google. Natural link growth tends to be gradual, with occasional spikes when a piece of content goes viral or gets picked up by a major publication. A consistently unnatural growth pattern can trigger manual review. I've seen this in Google Search Console, where a site will receive a manual action for "unnatural links pointing to your site." Recovering from that involves disavowing the bad links and submitting a reconsideration request, and it's not a fun process.

Checking Your Own Backlink Profile

If you want to see what your backlink situation actually looks like, you've got several options. Google Search Console shows you some of your backlinks for free under the Links report. It's not exhaustive — Google doesn't show you everything they know about your links — but it gives you a reasonable overview of your top linking sites and most-linked pages. For more detailed analysis, Ahrefs, Moz, and Semrush all have backlink analysis tools that crawl the web independently and maintain their own link indexes. Ahrefs tends to have the largest index in my experience, but they're all useful. You can see things like your total backlinks, referring domains, the authority distribution of your linking sites, your most common anchor texts, new and lost links over time, and more.

When I'm looking at a site's backlink profile for the first time, here's what I pay attention to: the ratio of dofollow to nofollow links (a healthy profile has both, but you want a solid portion of dofollow), the diversity of referring domains, whether the links are coming from topically relevant sites, the anchor text distribution (looking for keyword stuffing), and the trend over time (is the site gaining or losing links?). I also look for any obviously spammy links — links from foreign-language gambling sites, link farms, or other sketchy sources — because those might be doing more harm than good.

Toxic backlinks are a real concern for some sites. If you've inherited a site with a history of black-hat link building, or if a competitor has engaged in negative SEO against you (building spammy links to your site deliberately), you might need to clean up your backlink profile. Google's Disavow Tool lets you tell Google to ignore specific links or entire domains when evaluating your site. It's a blunt instrument and Google has said that for most sites, their algorithms are good enough at ignoring bad links automatically. But in cases where you've received a manual penalty for unnatural links, the disavow tool becomes important. You might also find Dofollow vs Nofollow Links: What's the Difference? useful here.

One more thing that doesn't get talked about enough: backlinks decay. Links you acquired three years ago might not exist anymore. Sites go offline. Pages get restructured. Content gets deleted. If you check your Ahrefs Lost Backlinks report, you'll probably find that you're losing links all the time. This is normal and expected, but it means that link building isn't a one-time activity. Even maintaining your current rankings requires ongoing link acquisition to replace the links that naturally fall off over time. Some estimates suggest that the average webpage loses about 5-10% of its backlinks per year, though I'm not sure how rigorous those numbers are.

The relationship between backlinks and rankings is also not purely linear or immediate. I've added links to pages and seen ranking improvements within days. I've also added links and seen absolutely nothing change for months. There are so many variables at play — the competitiveness of the keyword, the current authority gap between you and the pages outranking you, the quality and relevance of the specific links you acquired, whether Google has even processed those new links yet — that predicting the exact impact of any given link building effort is honestly kind of impossible. You're working with probabilities and general patterns, not certainties.

People really do overcomplicate this topic. The core of it is: get other reputable, relevant websites to link to your pages, and your pages will tend to rank better in Google. The details matter, the execution is hard, and there's genuine nuance in how you go about it. But the underlying principle hasn't really changed since Google launched. Links are votes of confidence. More quality votes from more diverse sources generally means better rankings. And despite all the changes Google has made over the years, despite all the new ranking factors they've introduced, links remain one of the pillars that the whole system stands on.