How Google could detect paid links

02 Aug 2012, Posted by admin in Featured,Google, 9 Comments

How Google could detect paid links

Google’s Penguin update, and the unnatural link warnings they’ve been sending out through Webmaster Tools, shows that they’re now looking to penalise suspicious & paid links instead of just devaluing them.

But the thing that really interests me is how Google determines which links are paid and which aren’t. If you’re an SEO, when you see a paid link, in most cases it’s generally pretty obvious if it’s unnatural or paid for – but it’s not as simple for a machine to detect.

There’s been some speculation as to what kinds of signals Google is looking at – sites that have the link warnings apparently tend to have a lot of sitewide links, most likely in footers and sidebars – and they also often have a very high keyword to brand anchor text ratio.

I’m not convinced that the ratio of anchor text used is enough to flag links as suspicious, at least not on it’s own. If the site or page doesn’t have that many links, then it’s a small sample size that could be easily skewed, and could lead to a lot of false positives. Another issue is that exact match domains would effectively get a free pass (although, that might still be true).

Time as a signal

I have a theory – and please note, this hasn’t been proven – that Google is looking at another signal to work out which links are suspicious. One of the big differences between paid links and natural links is when they’re placed. The majority of paid links are added to pages retroactively – i.e. a website has a page that mentions car insurance and a company might then approach them and offer to pay them on a monthly basis to change that text to a link.

I believe that if Google has crawled a page, and then at a later date recrawls that page and discovers a new link – with hardly any extra content added – that link is now flagged as suspicious. They might devalue it, they might send out a webmaster tools message or they might do both – but that link could well be flagged. The exception to this is if the page they’re crawling is the homepage, and potentially category pages, where content might change frequently.

If a reasonable chunk of text is also added at the same time as the link, then it potentially wouldn’t be flagged (so genuine updates to news articles wouldn’t accidentally flag that link).

How Google could deal with sidewide links

Other times, a paid link might be added to a sidebar in the form of a banner ad, or in a blogroll link, or as a link in the footer. These are, in 99% of cases, now sitewide links. They’d potentially trip the same filter as above, because those links would appear on pages that Google has already crawled, but there’d also be a higher percentage of false positives here (i.e. good links being flagged as bad) as bloggers often link to sites they genuinely endorse in blogrolls too.

If I were Google, I’d treat those links differently to deal with the increase in false positives. Unless I was confident that the link was classified correctly as either paid or natural, I’d consider silently devaluing that link and not sending out a link warning. After a time limit (maybe 6 months, maybe a year), I’d allow that link to start flowing Page Rank. If you’re buying links, you don’t want to pay for them and not have them work for months – you might be more likely to notice that the links you’re building aren’t working, so you stop renewing them. If it’s a genuine editorial link in a blogroll, then it’s more likely that that site can wait a while before getting the link value – because that link is mainly serving to pass them useful traffic.

“I’d like to get a few paid link reports anyway because I’m excited about trying some ideas here at Google to augment our existing algorithms” – Matt Cutts, 2007

I think this is probably something that Google have been doing for a while, way before the webmaster tools warnings were sent out. Matt Cutts mentioned in the past that they’ve been working on algorithms to automatically detect paid links, and I imagine there are probably other signals they’re looking at too.

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August 2, 2012 9:44 am

Patrick Hathaway

Nice theory. I’d like to think that time could be one of the triggers.

I guess the only place it may fall down is broken links – if they are replaced with a new, genuine link, this could potentially trigger? Although I guess if G can see that there was a link there previously and has now been replaced, that is different to a brand new link.

Also if you have a new resource that is linked to via a resources type page, I guess we don’t want that being penalised (presuming it is editorial).

If time is one of the triggers, what would the others be? Number of other links? Link location?

BTW I love the idea of potentially paid links not passing pagerank for 6 months.

August 2, 2012 12:18 pm

Paddy Moogan

Nice theory Dave, I just wanted to add something from my own testing on adding a link to old content.

I tried this back in early 2011 after a chat with a few people at a conference. I added exact match anchor text to old content and the links definitely made a difference in rankings to target pages. I didn’t edit the text, I just literally made some of the existing text a link.

That was last year, no idea if it would still work. I may test it though.

August 17, 2012 5:08 pm

Slavko Desik

Great article. I know that all is speculation when it comes to this, but these points do make sense. Except the obvious one that Patrick mentioned about adding a link in the resources area of a post.
I have a question though- Let’s say someone contacted me with a proposal of paying me for publishing a link on my site, with also adding a new content to go along with it. A new page, actually.
Can then Google detect that something is wrong? Since I cannot see a difference between such an action, and let’s say a guest post. The only thing that comes in mind is if Google evaluate the site that has been linked in terms of link profile.

My exact question would then be- can the actions by the site that has been linked in any way harm the site that gave the link? No matter whether we are talking about paid one or not.

November 19, 2012 5:54 am

Mark Walters

I think you’re right that the time a link was placed would be a good indicator of if it’s a paid link or not. That factor, along with the location of the link, if the link is relevant to the content and the anchor link text used for the link could probably highlight a good percentage of paid links. Some innocent links would no doubt get hit in the process though.

December 18, 2012 4:45 am

Oral Seymour

Google has tons and tons of data to comb through to see paterns. That’s why I laugh when I see link schemes like link wheels ect. If its takes me a few minutes to see then google can pick it up in no time.

July 26, 2013 10:57 am

Andy P of SEOTipsInfo

Interesting piece, although when it comes to Google a lot of the time they throw the baby out with the bathwater. For example if I were to offer a site some cash to put a new article on their site replacing old content on a high PR page that would be paid content but so hard to detect.
Google’s utopia of all natural links is honorable but is it realistic?

September 17, 2013 5:59 am

Cole Wiebe

Thanks for an interesting post. You’ve at least partially answered the question that’s been nagging me for some time. “How does Google know it’s a paid link?”

– Cole

September 23, 2013 12:39 pm


So. I’m quite new to SEO’s world and I’d like to ask you a question guys. Is Penguin going to penalize websites which have banner from which they get paid per click from sponsors (ppc)? I mean all this huge market is going to die? If I have a website with free content and got paid on how many clicks my banners receive (which are in the same niche of my site) am I going to see my site ranked lower or this will have no effect?

April 22, 2014 6:41 am


I think Google would ruin the industry if they decide to penalize site wide. big sites and authorities rely heavily on side wide links. wordpress, addthis, nickeldeon channel, godaddy are just a few names..

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