Google’s PBN Patent: Why 20 Sites Linking to You May Count as One

Say you build twenty websites, and each one links to your main site. That’s twenty links, right?

Under the Google patents in this article, they might count as one.

So far in this series, I’ve covered where a link sits on the page, where a link comes from on the web’s map, and when a link arrives. This article is about who is behind the link. It covers two related Google patents that describe how to spot sites controlled by the same owner, and how to shrink the votes they pass to each other. You can watch the full video breakdown below.

The Two Patents at a Glance

This article covers two related patents. The first is US 8,719,276, “Ranking nodes in a linked database based on node independence.” The second is US 7,783,639, “Determining quality of linked documents.”

Detail	US 8,719,276	US 7,783,639
First filed	November 2003 (provisional)	June 30, 2004
Granted	May 6, 2014	August 24, 2010
Inventors	Paul Haahr, Martin Kaszkiel, Amit Singhal	Krishna Bharat, Amit Singhal, Paul Haahr
Later versions	None	Continuations granted in 2012 and 2014
Status	Expired	Expired

The names are worth a second look. Amit Singhal went on to lead Google Search for years. Krishna Bharat created Google News.

One note on the title. The patents never use the term “PBN,” short for private blog network. They describe clusters of affiliated sites controlled by a single entity, which is what most link builders mean when they say PBN.

The Problem: One Owner, Many Votes

The node independence patent spells out the problem. Site owners were shaping their link structure around how PageRank worked. Some were paying high-ranking sites to link to them. And commercial link farms were trying to push rankings up artificially.

Think of every link as a vote. The idea behind both patents is simple: one entity shouldn’t get to vote over and over again. Twenty sites run by one person are not twenty independent opinions.

But to stop that, Google first has to figure out which websites belong to the same entity. That is where the patents get specific.

How Google Decides Sites Are Affiliated

The patents describe grouping websites into clusters of affiliated sites. A cluster forms when there is a high probability the sites are all controlled by a single entity. Between them, the two patents name these signals:

Signal	What the patents describe	Patent
Ownership records	Common ownership information, such as a WHOIS lookup	8,719,276
Similar content	Sites that look alike in their text or structure	8,719,276
Link patterns	How tightly the sites link to each other	Both
Traffic patterns	Sites that many users visit in the same session	7,783,639
Hosting	Similar hostnames, or IP addresses whose first two or three numbers match	7,783,639
Manual input	Information entered by people directly	8,719,276

The IP address detail

The hosting signal is the most specific one. The second patent says that if the first two or three numbers of two servers’ IP addresses are the same, affiliation can be inferred. For example, 203.0.113.24 and 203.0.113.87 share their first three numbers.

The bigger point is that there is no single signal to hide. Changing your domain registration details covers one signal out of many. The content, the structure, the linking, the traffic and the hosting can all still point back to the same owner.

The Math That Collapses a Network

Once sites are grouped into a cluster, the patents describe two ways to shrink their votes.

Rule 1: Divide the vote

The first patent gives an example. A page gets a full vote of 1.0 from an independent site. But when the page sits in a three-site affiliated cluster, each vote it gets from the other two sites in that cluster is divided by three, down to about 0.33 each.

Rule 2: Keep only the strongest vote

The second rule is even stronger. If several sites in the same cluster all link to one page, only the strongest of those votes counts. The rest are dropped.

That is the “twenty sites, one vote” rule from the start of this article. And it is not just a passing idea in the description. It is written into the claims of the patent, the part that defines what the patent actually protects.

One Author, Three Links

If networks collapse, what kind of links actually add up? The second patent answers with a simple example.

Three pages written by the same author all link to one page. Two other pages, from two different authors, link to it too. The patent’s reasoning is that three links from the same author don’t make the page three times as good. But the two independent links are different. The patent says they complement each other, so their value stacks.

Affiliation is not all or nothing

The patent also treats affiliation as a matter of degree. Sites on the same host can count as strongly affiliated. Sites with weaker evidence can count as weakly affiliated. The more independent two sites are, the more their votes add up.

That is why a wide spread of genuinely independent sources is so valuable, and why real independence is hard to fake. For more on building links at volume without cutting corners, read the truth about scalable link building.

The Cap and the Trusted Authorities

The first patent adds one more rule. No single site can pass more than a full vote. So even a huge site with an enormous number of links pointing at it cannot completely dominate the sites it links to.

But there is a twist. Sites that reach what the patent calls a trusted authority level can give a full vote to every site they link to, no matter how many outbound links they have. The patent says this discourages sites from hoarding their rank by linking to only a few places.

In the seed site article, I explained why pages with fewer outbound links tend to pass more value. For ordinary sites, that still holds. But in this design, a truly trusted authority’s link isn’t watered down by the other links on the page.

What This Means for Your Link Building

Here is what these patents suggest for anyone building links.

1. Count independent organizations, not referring domains

Ten links from sites owned by one company may add up to about one. When you review a backlink profile, group the linking domains by who actually owns them.

2. Don’t build a network

Links from sites you own or control collapse, no matter how many of them there are. Google’s spam policies also name partner pages built only for cross-linking as link spam.

Excessive link exchanges (‘Link to me and I’ll link to you’) or partner pages exclusively for the sake of cross-linking.

— Google Search Central · Spam policies · Google Search Central: Spam Policies for Google Web Search

3. Hiding ownership isn’t enough

The patents name signals far beyond domain registration records: content, structure, linking patterns, traffic and hosting. Masking one of them does not hide the others.

4. Go after links from truly independent sources

Independent endorsements are the ones that stack. Aim for links from many different organizations, not many sites from a few.

5. Earn links from trusted authorities

In this design, a trusted authority’s links can pass a full vote, even when the page links out a lot.

6. Cross-link your own properties for users, not rankings

Linking your own sites together is fine for navigation and for helping visitors. Just don’t expect it to move your rankings.

The Honest Caveat

A patent shows what Google invented and chose to protect. It does not prove this exact system runs in Google’s algorithm today. Both of these patents have now expired.

Still, the ideas in them have been public for more than twenty years, and they came from people who went on to run Google Search.

Conclusion

These patents come down to one idea: who is behind a link matters. Google described ways to spot sites controlled by the same owner, divide their votes, and count only the strongest one. Twenty links from one owner may be one vote. Twenty links from twenty independent sites are twenty.

Where a link sits matters. Where it comes from matters. When it arrives matters. And who is behind it matters too.

Next in this series, I look at Google’s link spam detection patent, and the clever “wobble test” it uses to tell a link farm from a genuinely popular site.

Want links from truly independent sites? Talk to Link Builders about your next campaign.

Sources

• US 8,719,276: Ranking nodes in a linked database based on node independence, Google Patents
• US 7,783,639: Determining quality of linked documents, Google Patents
• Spam policies for Google web search, Google Search Central

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