What Are Backlinks? What Google Actually Says They Do, and the Link Arithmetic Behind Them
· Royking Niba
Backlinks are links on other websites that point to a page on your website. If a news site writes about your business and links to your homepage, that link is a backlink for you. Google uses backlinks in two documented ways: to discover pages it has not crawled yet, and as one signal of what a page is about and how useful it might be. Below is Google’s own wording on both, a table of which kinds of backlink are fine and which break Google’s link spam policy, and a worked model of the original PageRank idea that explains why one link can be worth far more than another.
What Google says links are for
Google’s link best practices page, last updated 10 December 2025 and checked today, opens with the clearest single sentence Google has published on the subject:
Google uses links as a signal when determining the relevancy of pages and to find new pages to crawl.
Google Search Central, link best practices
Two jobs, then. The first is discovery: Googlebot follows links, so a page nobody links to is harder for Google to find, which is the whole subject of my post on orphan pages. The second is relevancy, and that is where backlinks earn their reputation. Google’s guide to its ranking systems, also last updated 10 December 2025, names the system behind it:
We have various systems that understand how pages link to each other as a way to determine what pages are about and which might be most helpful in response to a query. Among these is PageRank, one of our core ranking systems used when Google first launched.
Google Search Central, a guide to Google Search ranking systems
The same guide adds that how PageRank works “has evolved a lot since then, and it continues to be part of our core ranking systems.” So backlinks matter, Google says so in writing, and nobody outside Google knows the current formula. Anyone who tells you exactly how much one link is worth is guessing.
Backlinks, internal links and outbound links
| Link type | From | To | Who controls it |
|---|---|---|---|
| Backlink (inbound link) | Another website | Your website | The other site’s owner |
| Internal link | Your website | Your website | You |
| Outbound (external) link | Your website | Another website | You |
Every backlink you have is somebody else’s outbound link. That symmetry is why Google’s spam policy talks about links “to or from” a site, and why there are two separate unnatural links manual actions, one for each direction. Internal links follow the same mechanics but sit entirely under your control, which I cover in internal linking for SEO.
Which backlinks are fine and which break the rules
Google’s spam policies, last updated 28 August 2026, define the problem in one sentence: “Link spam is the practice of creating links to or from a site primarily for the purpose of manipulating search rankings.” They also make clear that paying for a link is not the violation in itself: “It’s not a violation of our policies to have such links as long as they are qualified with a rel=”nofollow” or rel=”sponsored” attribute value.” The table below sorts the common kinds of backlink by what Google’s documentation says about them. The rel values come from Google’s page on qualifying outbound links.
| How the backlink came about | Attribute Google asks for | Within Google’s policy? |
|---|---|---|
| A journalist or blogger links to your page because it is useful | None needed | Yes. This is the link Google’s systems are built to reward |
| You paid for an advertisement or sponsored placement with a link | rel=”sponsored” (or nofollow) | Yes, if qualified. No, if it passes ranking credit |
| A visitor posts your link in a comment or forum thread | rel=”ugc” recommended | Yes, unless the comments are placed to manipulate rankings |
| You swapped links with a partner site to rank, at scale | Not fixable by attribute alone | No. Excessive link exchanges are a listed example |
| You bought a guest post with a keyword-rich link that passes credit | Would need sponsored or nofollow | No, as published. Advertorials with paid links are a listed example |
| An automated tool or service created the links | Not fixable by attribute alone | No. Automated link creation is a listed example |
| Low-quality directory or bookmark site listings | Not fixable by attribute alone | No. Named in the policy’s examples |
| A network of sites you control linking to your money site | Not fixable by attribute alone | No. See PBN backlinks |
Google defines the attributes in plain terms. Sponsored is for links “that are advertisements or paid placements (commonly called paid links)”. UGC is recommended for “user-generated content (UGC) links, such as comments and forum posts”. Nofollow is for when “other values don’t apply, and you’d rather Google not associate your site with, or crawl the linked page from, your site.” You can combine values in one attribute, separated by a space or a comma.
A worked model: why one link is worth more than another
This is a teaching model, not a measurement of how Google ranks pages today. It uses the formula from the 1998 Stanford paper in which Sergey Brin and Larry Page described PageRank, where a page passes its score to the pages it links to, split evenly across its outgoing links and multiplied by a damping factor the paper set at 0.85. Google has said the system has changed a great deal since. What survives, and what the model makes visible, is the dilution principle.
Assumptions, all mine and labelled: the linking page has a score of 1.00, every one of its outgoing links counts equally, and nothing else about the link (position, anchor text, relevance) changes. The only variable is how many links leave the page.
| Outgoing links on the linking page | Share passed to each linked page (0.85 divided by links) | Relative to a page with one link |
|---|---|---|
| 1 | 0.850 | 100% |
| 5 | 0.170 | 20% |
| 10 | 0.085 | 10% |
| 50 | 0.017 | 2% |
| 100 | 0.0085 | 1% |
| 300 | 0.0028 | 0.33% |
Under this model, one link from a focused article with five outgoing links passes the same share as twenty links from pages carrying a hundred outgoing links each, because twenty times 0.0085 is 0.17. That is the arithmetic behind the advice to chase a few editorial links instead of hundreds of directory and footer links, and it is also why link farms that put hundreds of outbound links on a page were never a good deal even before Google classed them as spam. The model’s limits are real: modern Google weighs links in ways it does not publish, a link’s relevance and placement almost certainly matter, and a strong page with many links can still pass more than a weak page with few. Treat the table as an explanation of why quantity alone is a poor goal, not as a calculator.
What a good backlink looks like
- It exists because someone chose to cite you. Google’s link best practices page says linking out “can help establish trustworthiness (for example, citing your sources)”. The backlinks worth having are the citations other writers make for that reason.
- It sits in content about your subject. Google says it uses links to understand “what pages are about”, so a link from a page on your topic tells it more than a link from an unrelated page.
- Its anchor text describes the destination. Google’s guidance is to write anchor text that makes sense on its own and to avoid stuffing it with keywords, which its spam policies treat as a violation.
- It is on a page people actually read. A page that earns its own links and traffic has something to pass on. A page made to hold links has very little.
When backlinks become a problem
Most sites never need to think about bad backlinks. Google’s systems ignore a large amount of junk on their own, and an ugly link is not the same as a harmful one, a distinction I go into in toxic backlinks. Backlinks become your problem when you or someone working for you built them to manipulate rankings, because that is the pattern Google’s manual reviewers act on. If Search Console shows a links manual action, the fix is removal first and the disavow file second, in that order. If you suspect someone is pointing spam at you deliberately, read negative SEO attacks before you disavow anything. And if traffic has already fallen and you do not know why, start with my Google penalty recovery guide, which walks through telling a links problem apart from everything else that can cause a drop.
Related reading
- Google Penalty Recovery: how I diagnose and reverse a traffic collapse
- Unnatural links: the two manual actions Google names
- Toxic backlinks: how I tell a real problem from an ugly one
- PBN backlinks and why networks get caught
- Internal linking for SEO
- Google Business Profile suspended: the appeal process and the evidence Google accepts
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