What Is Backlink?

How Backlinks Work

Every backlink is a small piece of borrowed credibility. When another site links to your page, its author is implicitly telling readers — and search engines — that your page is worth going to. Because the author is not you, that endorsement carries weight your own claims cannot: anyone can call their page authoritative, but a link from a respected outside source is harder to fake. This is the intuition search engines industrialized.

The mechanics run in two directions. First, links are how search engines find the web at all. Google’s own documentation describes discovering new pages by extracting a link from a known page to a new one, so a page with no incoming links is hard for a crawler to reach. Second, once a page is known, the links pointing at it feed into how it ranks. The link graph — the map of who links to whom — is treated as a resource for judging quality, not just a set of navigation paths.

Not every backlink passes the same value, and some pass none on purpose. A standard editorial link is followable and transfers ranking signal. A link carrying rel="nofollow", rel="sponsored", or rel="ugc" tells search engines not to treat it as an endorsement, which is why paid or user-generated links are expected to be marked. And links built primarily to game rankings fall under Google’s link spam policies, where they are discounted or penalized rather than counted.

Types of Backlinks

Backlinks are usually sorted along two axes — how much signal they pass, and how they were earned:

• Followed (dofollow) links — the default. They pass ranking signal and are what most link-building aims to earn.
• Nofollow / sponsored / ugc links — carry a rel attribute that tells engines not to pass full endorsement. Still useful for traffic and discovery, but weak as a ranking vote.
• Editorial links — placed by a writer because your page genuinely helped their content. These are the links Google’s guidance treats as legitimate.
• Manual or self-placed links — directory entries, forum signatures, comment links. Low value at best; link spam at worst if done at scale to manipulate rankings.

The anchor text of a backlink — the visible, clickable words — adds context about what the target page is about, which is why natural, varied anchors read as more trustworthy than the same exact-match phrase repeated across thousands of links.

Example of Backlinks

The cleanest real illustration of what a backlink is comes from the document that named it. In their 1998 paper The Anatomy of a Large-Scale Hypertextual Web Search Engine, Sergey Brin and Larry Page described the prototype that became Google and wrote that “academic citation literature has been applied to the web, largely by counting citations or backlinks to a given page,” which “gives some approximation of a page’s importance or quality.” The web, in their framing, was a giant citation network, and a backlink was the web’s version of one paper citing another.

The crucial detail — the one most people skip — is what came next. Brin and Page immediately noted that their PageRank method “extends this idea by not counting links from all pages equally, and by normalizing by the number of links on a page.” In other words, from the very first design, a backlink was never worth a flat one point. A link from a page that itself is important, and that links out sparingly, counts for far more than a link from a page nobody cites that links to everything. The vote is weighted by the voter.

That weighting is why raw counts mislead. Google’s John Mueller has said publicly that the total number of links to a site is not what decides rankings — that a site could manufacture millions of links and have them all ignored, while “one really good link from one website” can be the signal that matters. The 1998 math and the 2020s guidance agree: a backlink’s value lives in the trust and selectivity of its source, not in the size of the pile. The takeaway for anyone building or auditing links is to evaluate each backlink the way the original algorithm did — as a weighted endorsement — instead of adding them up.

Backlink vs Internal Link

Both are hyperlinks, and both influence SEO, but they answer different questions and are controlled by different people.

The short version: a backlink is an outside vote you have to earn, while an internal link is a routing and relevance decision you make yourself. Conflating them leads people to treat their own internal links as if they conferred outside authority — they don’t.

Frequently Asked Questions

The Bottom Line

A backlink is an outside site vouching for your page with a link — the web’s original trust signal, borrowed from how academic papers cite each other. Its value was never in the count but in the source: a handful of deliberate, editorial links from selective sites tells a search engine more than a warehouse of automated ones, which is why the smart unit of measurement is the referring domain and the reason behind the link, not the tally.